Skip to content

karapish/blockchain

BranchesTags

Repository files navigation

ERC-20 Ownable Token with Mint & Burn

Overview

This smart contract implements a fungible token with:

  • Full ERC-20 standard interface (EIP-20)
  • Ownership control (via Ownable)
  • Minting (only owner can mint new tokens)
  • Burning (token holders or approved spenders can burn tokens)

Specification

Interfaces & Behavior

Component Methods / Events Access Control / Requirements
ERC-20 totalSupply(), balanceOf(address), transfer(address,uint256), approve(address,uint256), transferFrom(address,address,uint256), allowance(address,uint256)
Events: Transfer, Approval		 Standard checks: non‐zero addresses, sufficient balances, allowance logic, etc.
Ownable owner(), onlyOwner modifier, transferOwnership(address), optionally renounceOwnership() Owner set at deployment; only owner can call owner-only functions.
Minting mint(address to, uint256 amount) Only owner can mint; cannot mint to zero address; total supply increases.
Burning burn(uint256 amount), burnFrom(address account, uint256 amount) Holders (or approved spender) can burn; sufficient balance; total supply decreases.

Security & Constraints

  • Prevent operations involving zero address.
  • Ensure safe arithmetic (overflow/underflow) — use Solidity ≥0.8 or libraries.
  • Emit appropriate events: for mint, a Transfer(0x0, to, amount); for burn, Transfer(account, 0x0, amount).
  • Ownership functions protected via onlyOwner.
  • Do not allow minting/burning beyond expected logical constraints (if any).

Out of Scope

Unless added explicitly, the contract does not include:

  • Role-based access beyond single owner (e.g. separate minters or burners)
  • Supply cap / maximum supply
  • Pausing or freezing transfers
  • Permit / meta-transaction support
  • Snapshot / voting / staking or other extensions

Example Implementation Snippet

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract MyToken is ERC20, Ownable {
    constructor(string memory name, string memory symbol) ERC20(name, symbol) {
        // optionally initial minting
    }

    function mint(address to, uint256 amount) public onlyOwner {
        _mint(to, amount);
    }

    function burn(uint256 amount) public {
        _burn(msg.sender, amount);
    }

    function burnFrom(address account, uint256 amount) public {
        uint256 currentAllowance = allowance(account, msg.sender);
        require(currentAllowance >= amount, "ERC20: burn amount exceeds allowance");
        _approve(account, msg.sender, currentAllowance - amount);
        _burn(account, amount);
    }
}

ERC-20 Required Functions & Events

Below are the mandatory methods and events a contract must implement to comply with ERC-20. (Optional metadata functions are not listed here.)

⚙ Required Methods

Function Signature Visibility & Return Types Purpose / Requirements
totalSupply() function totalSupply() public view returns (uint256) view, returns total number of tokens in existence. oai_citation:0‡Ethereum Improvement Proposals
balanceOf(address _owner) function balanceOf(address _owner) public view returns (uint256 balance) view, returns the balance of _owner. oai_citation:1‡Ethereum Improvement Proposals
transfer(address _to, uint256 _value) function transfer(address _to, uint256 _value) public returns (bool success) non-view; transfers _value tokens from caller to _to. Must emit Transfer. Should fail (revert) on insufficient balance. Zero-value transfers allowed. oai_citation:2‡Ethereum Improvement Proposals
approve(address _spender, uint256 _value) function approve(address _spender, uint256 _value) public returns (bool success) non-view; caller sets allowance for _spender to spend up to _value from caller’s account. Should emit Approval. May overwrite existing allowance. oai_citation:3‡Ethereum Improvement Proposals
allowance(address _owner, address _spender) function allowance(address _owner, address _spender) public view returns (uint256 remaining) view; returns remaining amount _spender is allowed to withdraw from _owner. oai_citation:4‡Ethereum Improvement Proposals
transferFrom(address _from, address _to, uint256 _value) function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) non-view; moves _value tokens from _from to _to, where the caller has sufficient allowance. Must reduce allowance accordingly. Must emit Transfer. Zero value transfers allowed. oai_citation:5‡Ethereum Improvement Proposals

🗳 Required Events

Event Signature When to Emit
Transfer(address indexed _from, address indexed _to, uint256 _value) event Transfer(address indexed _from, address indexed _to, uint256 _value) Emit on any token transfer. Also emit when tokens are minted (i.e. from address 0x0 → recipient) or burned (recipient is 0x0). Zero value transfers still emit. oai_citation:6‡Ethereum Improvement Proposals
Approval(address indexed _owner, address indexed _spender, uint256 _value) event Approval(address indexed _owner, address indexed _spender, uint256 _value) Emit whenever approve(...) is called successfully. oai_citation:7‡Ethereum Improvement Proposals

📌 Notes & Requirements

Who Pays Gas When You Invoke a Non-View Function via MetaMask

  1. You send a transaction (non-view function call) through MetaMask.
  2. You (the sender) pay for the gas.
  3. The payment comes from your wallet address (the account you used in MetaMask).
  4. MetaMask will show you an estimate for the gas cost before you confirm.
  5. If your wallet doesn’t have enough ETH to cover the gas, the transaction will fail or won’t be sent.

🔍 Additional Details

  • Gas cost = gasUsed × gasPrice (or with EIP-1559: base fee + priority tip).
  • Even if the transaction fails (e.g. reverts), you still pay gas for the work done up until the failure.
  • The recipient of a transaction doesn’t pay the gas. The gas always comes from the sender (unless some contract logic reimburses them later, but that’s extra).

Here’s a walkthrough (in Markdown) of the Ethereum send() / transaction signing & lifecycle process, covering who signs what, what RPC does, validation, rejection, etc.

⸻

Ethereum Transaction Send / Signing Lifecycle

Below is a step-by-step of what happens when you invoke a non-view function (via send()), from signing to inclusion in a block.

1. What parties sign

  • Externally Owned Account (EOA): the user who owns the private key of the sending address signs the transaction.
  • No other party signs by default. Only the private key of the sender is used to generate a digital signature over the transaction contents (nonce, gas limit, gas price / tip, to, value, data, chain ID). oai_citation:0‡Medium
  • If using a wallet such as MetaMask, the wallet UI will ask you to confirm, then uses your private key (or hardware wallet) to sign.

2. Will RPC be invoked?

  • After signing locally, the signed transaction is sent (broadcast) to the Ethereum network via an RPC endpoint (e.g. via eth_sendRawTransaction) or via a provider (like Infura, Alchemy, or your own node). oai_citation:1‡Alchemy
  • The local client (wallet / Web3 library) constructs the transaction object, signs it, serializes it (often RLP encoding), then invokes an RPC call to submit the signed transaction. oai_citation:2‡Medium

3. What party is accountable for validation and rejection

  • Sender / wallet: ensures correct parameters (e.g. nonce, gas limit, to address, data) before signing. If something is invalid, the client/wallet may reject locally (e.g. bad address, insufficient funds).
  • RPC node / Ethereum node/network: once submitted, the node that receives the transaction validates it. Validation includes checks like:
    • Is signature valid?
    • Is the nonce correct (not replaying or too low)?
    • Does the sender have enough ETH for gas + value?
    • Is gas price acceptable?
    • Is chainId correct?
  • If any validation fails, the transaction is rejected (not included in the mempool). The node may reply with an error.

4. Lifecycle of the transaction (if it passes initial validation)

  1. Mempool / Transaction Pool
  • After passing basic checks, the transaction sits in the node’s transaction pool (mempool) waiting to be picked up by a miner (or validator, depending on consensus).
  1. Mining / Including in Block
  • A miner/validator picks the transaction (often based on gas price / tip) and includes it in a new block.
  1. Block Propagation
  • The block is propagated to other nodes.
  1. State Execution
  • When the block is executed, the transaction executes the specified function on contract (non-view), updating state. Gas is consumed.
  1. Receipt
  • A transaction receipt is generated, containing status (success/failure), gas used, logs/events, etc.
  1. Confirmation
  • Once the block is part of the canonical chain and many more blocks are built on top, the transaction is considered confirmed.

✅ Summary

  • The sender signs with their private key.
  • RPC is invoked to submit the signed transaction.
  • Nodes validate and can reject if invalid.
  • If valid, the tx enters the mempool, then eventually included in a block, executed, and you get a receipt.

✅ How to determine the correct nonce

You generally fetch the nonce by querying the network for the account’s transaction count. Key options:

  • Using RPC / provider:
    Call eth_getTransactionCount(address, "pending") — this returns confirmed + pending transactions (so you can safely use the next nonce).

  • Alternative:
    Call eth_getTransactionCount(address, "latest") (only confirmed ones), but this may cause collisions if you have pending txs.

⚠️ What to watch out for

  • Pending transactions:
    If you already submitted txs that aren’t mined, their nonces are reserved. Using the same nonce will cause conflicts or rejection.

  • Skipping nonces:
    If you pick a nonce higher than current + 1 (leaving gaps), that tx stays pending until all prior nonces are mined. Later txs are blocked until gaps are filled.

  • Concurrency:
    If multiple processes/wallets send txs from the same address, they may race for nonces. Use shared state or locking to avoid clashes.

🛠 Best practices

  • Always query "pending" nonce from your provider before creating a tx.
  • If you have a queue of txs, track nonces locally so you know what’s reserved even if not confirmed.
  • If a tx is stuck or pending too long, replace it by submitting a new tx with the same nonce but higher gas (replace-by-fee).
  • Use libraries / SDKs / frameworks that help with nonce management (e.g. ethers.js, web3.js, Nethereum, or backend systems) to avoid manual handling.

SDKs

  • ethers.js
  • web3.js
  • Nethereum

When you send a transaction to a node (RPC / full node), it goes through several validation steps before being accepted into the node’s mempool. These checks help ensure that bad/fraudulent transactions are filtered out.

Here are key checks / steps:

Step What is Checked Why It Protects
Signature correctness The transaction must have a valid digital signature matching the claimed sender address. Prevents spoofing / forging of transactions.
Nonce correctness The nonce must be ≥ the account’s current nonce; usually from eth_getTransactionCount(..., "pending"). Avoids replay or out-of-order or duplicate tx issues.
Balance check Sender must have enough ETH to cover value + gas limit × gas price (or max fees). Prevents transactions that would overspend.
Gas limit & fees Gas limit must be valid; fees must meet minimal rules, etc. If gas price is too low, some nodes may decline or drop. Prevents spam / DoS with extremely underpriced txs.
Basic format checks RLP-serialization correctness; fields present; chain ID matching; etc. Ensures malformed txs are rejected early.
Consensus rules The tx must not violate protocol or client-specific rules (e.g. EIP rules, gas rules, chain rules). Prevents invalid state transitions.

✅ Transaction Flow & Types

  • Only valid transactions enter your node’s mempool and get broadcast.
  • Other nodes revalidate them during propagation.

🔹 Types of Ethereum transactions

  • Contract deployment
  • Human-to-human (EOA → EOA)
  • Contract-to-contract (internal)
  • Hybrid (e.g., DeFi use)

🔹 Transaction states

  • Pooled / Mined / Dropped / Replaced
  • Canceled – replacement that cancels the original
  • Confirmed – mined & included on-chain
  • EOA – between Externally Owned Accounts
  • Failed – attempted but didn’t succeed
  • Internal – smart contract ↔ smart contract
  • Private – sent directly to a miner (skip mempool)
  • Stuck – pending, can’t be mined
  • Type 0 – legacy (pre-EIP-1559)
  • Type 2 – EIP-1559 format

🔌 Ethereum Wire Protocol: Full Node Tasks

All full nodes on Ethereum have three basic tasks with the Wire protocol:

  1. Synchronization – Download and verify headers, blocks, and state to stay in sync.
  2. Block Propagation – Share new blocks with peers for fast global consensus.
  3. Pending Transaction Propagation – Gossip unconfirmed transactions from mempool to peers.

Ethereum transactions are propagated across a decentralized Peer-to-Peer (P2P) network using protocols like RLPx and the Wire Protocol, ensuring block producers and validators can find pending transactions in the mempool. Nodes discover each other using bootnodes and establish secure connections using the RPLx protocol. They synchronize state, blocks, and pooled transactions using the Wire protocol

Nodes propagate transactions by signaling new transactions via the NewPooledTransactionHashes message, or peers can query for these transactions using the GetPooledTransactions message. Since The Merge, the consensus layer client receives, pre-validates, and passes blocks to the execution layer client, which executes transactions, validates the block’s state, and sends the validated block back to the consensus layer client for broadcasting.

Our actors in Ethereum’s transaction flow

⚡ Front-running bots

  • Monitor the public mempool for profitable opportunities.
  • When they see a big trade, they send their own tx with higher gas so it executes first.
  • Example: You buy a token → bot buys before you → raises price → sells after (sandwich attack).

📊 MEV searchers

  • MEV = Maximal Extractable Value.
  • More advanced than simple bots: scan mempool or use private relays (e.g., Flashbots).
  • Bundle profitable txs (arbitrage, liquidations, sandwiching) → submit to validators.
  • Compete in an “MEV auction” by paying higher fees.

🧑‍⚖️ Validators

  • Block proposers in Ethereum Proof-of-Stake.
  • Decide which mempool txs (public/private) to include in blocks.
  • Profit motive: maximize rewards via priority fees + MEV bundles.
  • Can cooperate with searchers via MEV relays (e.g., Flashbots).

🔍 Explorers

  • Tools like Etherscan to observe mempool and chain state.
  • Show pending txs, gas prices, activity.
  • Don’t seek profit directly but provide transparency that bots/searchers also use.

✅ In short:

  • Front-running bots = simple opportunists.
  • MEV searchers = advanced profit optimizers.
  • Validators = decide final tx ordering/inclusion.
  • Explorers = observers giving visibility.

Ethereum Transaction Types & EIP-1559

  • Type 0 (Legacy): Transaction format from before EIP-1559. Uses a single gasPrice field. Still valid and accepted.
  • Type 2 (EIP-1559): Introduced in the London hard fork. Uses maxFeePerGas + maxPriorityFeePerGas + base fee mechanics. Default/preferred now.
  • Backwards compatibility: Legacy transactions continue to work even after EIP-1559.

🔹 Full Node

  • Stores full blockchain data (headers, blocks, state).
  • Verifies all transactions and blocks against consensus rules.
  • Relays valid txs/blocks across the p2p network.
  • Does not create new blocks.

🔹 Miner (Proof-of-Work era, pre-Merge)

  • A full node plus block production role.
  • Used computational power (hashing) to solve puzzles.
  • If successful, produced a block → earned block reward + fees.

🔹 Validator (Proof-of-Stake, post-Merge)

  • A full node plus staking-based block proposer role.
  • Selected randomly (weighted by stake) to propose/attest blocks.
  • Earns rewards from priority fees, MEV, and issuance.

✅ In short:

  • Full node = verifies & relays.
  • Miner (old) / Validator (current) = full node + block producer role.

🔹 How MEV Searchers Operate

  1. Transaction Monitoring
  • Run their own Ethereum nodes or use private relay feeds.
  • Continuously scan pending txs in the public mempool.
  • Identify profitable patterns: arbitrage, liquidations, sandwich opportunities.
  1. Simulation
  • Use custom bots to simulate “what if I insert my tx here?”
  • Run many simulations to estimate profit vs. cost (gas, risk).
  1. Bundling & Submission
  • Craft bundles of transactions (their tx + victim tx + closing tx).
  • Submit via:
    • Public mempool (fast, higher gas to outbid others).
    • Private relays (e.g. Flashbots) → avoid leaking strategy to bots.
  1. Competition
  • Multiple searchers compete in a “MEV auction.”
  • Offer higher priority fees or direct payments to validators.
  • Validator includes the most profitable bundle.
  1. Execution
  • If chosen, their transactions execute in the exact order they planned.
  • Profit goes to the searcher; validator earns the tip.

🔹 Community & Communication

  • Searchers are organized and often work semi-professionally.
  • Public discussion happens in research forums (e.g., Flashbots forum).
  • Academic papers, GitHub repos, and blogs explain MEV strategies in theory.
  • Anything like “special Discord channels” does exist, but they are private, competitive, and not open to the public — most professional MEV actors guard strategies closely.

✅ In short:
MEV searchers are like quant traders for Ethereum → scanning txs, simulating outcomes, and competing to pay validators for profitable order flow.

🔹 Private Relays in Ethereum

  • What they are

    • Network services that let MEV searchers send transaction bundles directly to validators, skipping the public mempool.
    • Part of the MEV-Boost / PBS (Proposer-Builder Separation) ecosystem.

  • Why they exist

    • Prevents strategies (arbitrage, liquidations, sandwiches) from being copied by other bots.
    • Reduces risk of front-running in the public mempool.
    • Lets validators earn more by receiving optimized bundles.

  • How they work

    1. Searcher → submits bundle to builder (via private relay).
    2. Builder → constructs a block with most profitable tx ordering.
    3. Relay → forwards block proposal to validator.
    4. Validator → signs/attests block → includes on chain.

  • Examples

    • Flashbots Relay (most known).
    • bloXroute, Eden, Manifold, others.

✅ In short:
Private relays = “private pipelines” for transactions, used to protect MEV strategies and let validators choose the most profitable block proposals.

🔍 References on MEV Auctions

🔹 Base Staking Yield (Inflation-Only)

  • Where it comes from

    • Ethereum issues new ETH as rewards to validators for duties:
      • Attestations (voting on correct blocks)
      • Sync committee participation
      • Proposing blocks

  • Rate depends on validator count

    • The more validators there are, the more the total reward pool is split.
    • Each validator gets a smaller slice when participation grows.

  • Typical range

    • With current validator set (~1M+ active validators), base inflation rewards = ~3–4% APR.
    • This excludes execution-layer rewards (priority fees + MEV).

  • Key point

    • Inflation yield is the guaranteed, protocol-level reward.
    • Execution rewards (fees, MEV) sit on top and push APR higher (≈5–6% with MEV-Boost).

🔹 Why Ethereum Blockspace Feels Scarce

  1. Bidding wars
  • Open mempool = everyone competes on gas price.
  • Creates volatility, higher fees, and disadvantages for regular users.
  1. All-pay auction problem
  • Even failed bids consume blockspace (reverted txs still included).
  • Bidders underprice to reduce risk, lowering validator revenue.
  • Artificial scarcity emerges.
  1. Limited bidding language
  • gasPrice (Type 0) or simple fee bidding doesn’t allow fine ordering preferences.
  • Users resort to spamming or brute-force strategies.
  • Wastes blockspace and adds network load.

✅ In short: Blockspace is scarce not just because of technical limits, but also due to inefficient auction design in the public mempool.

🔹 Execution vs. Consensus Clients

  • Execution client (e.g., Geth, Nethermind)

    • Runs the EVM, processes transactions, updates balances and state.

  • Consensus client (beacon node, e.g., Prysm, Lighthouse)

    • Runs Proof-of-Stake consensus.
    • Relies on the execution client for transaction validity and state.

🔹 When a block has a failed transaction

  • The execution payload in the block contains all transactions.
  • Execution client applies them sequentially:
    • Reverted tx → sender loses gas, no other state changes.
    • Successful tx → balances and contracts updated.

🔹 How the beacon node learns

  1. Beacon node receives the new block from the proposer.
  2. Forwards the execution payload to its paired execution client.
  3. Execution client updates balances and state.
  4. Beacon node checks that the resulting state matches the block’s root.

✅ In short:

  • The execution client updates wallet balances.
  • The beacon node only coordinates consensus and validates that the execution client’s result is correct.

🔹 Ethereum’s Account Model

  • Ethereum uses an account-based model (not UTXO like Bitcoin).
  • Each account has:
    • Address
    • Nonce
    • Balance
    • Storage root (for contracts)
    • Code hash (for contracts)

🔹 World State

  • The EL client maintains a global world state = mapping of all accounts → their balances and data.
  • This state is stored in a Merkle Patricia Trie (state trie).
  • Root hash of the trie is included in every block header.

🔹 Syncing

  • When you run an EL client:
    • It downloads blocks from peers.
    • Applies all transactions in order.
    • Updates the state trie after each block.
  • Over time, the client reconstructs the entire Ethereum state.

🔹 Wallet visibility

  • The client doesn’t need to “track” wallets individually.
  • It just stores the entire state database (key-value store).
  • If you query eth_getBalance(address), the client looks up that address in its state trie.

✅ In short:
An EL client “knows all wallets” because it maintains the entire Ethereum state trie, updated with every block. Every balance, nonce, and contract is part of this global state, not something the client has to “discover” one by one.

🔹 Ethereum (ETH)

  • State storage: Merkle Patricia Trie (MPT) → maps addresses → accounts (balance, nonce, storage, code).
  • Persistence: Entire state is maintained continuously and updated with every block.
  • Size: As of 2025, the Ethereum world state is hundreds of GBs (≈250–350 GB depending on pruning).
  • Lifetime: Indefinite — state persists as long as accounts/contracts exist.

🔹 Ethereum Classic (ETC)

  • Same design as Ethereum (before upgrades like Verkle tries are introduced).
  • Uses the Merkle Patricia Trie for global state.
  • Size: A bit smaller than ETH because of less activity and fewer contracts.
  • Lifetime: Also indefinite — state grows with chain usage.

🔹 Bitcoin (BTC)

  • Different model: UTXO (Unspent Transaction Output) set.
  • No account trie — instead, it tracks all unspent outputs in a database (LevelDB/RocksDB).
  • Persistence: UTXO set is updated every block, like Ethereum’s state.
  • Size: Much smaller — ~10–15 GB today (since it only tracks spendable outputs, not contracts/storage).
  • Lifetime: Indefinite, updated as long as Bitcoin runs.

✅ In short:

  • ETH & ETC → use a Merkle Patricia Trie to store the full account-based world state, continuously updated, and now hundreds of GB in size.
  • BTC → uses a UTXO set instead, stored in a database, smaller (~10–15 GB).
  • In all cases, this state is kept forever, updated at each block, because it’s the reference for validating new transactions.

🔹 Ethereum / Ethereum Classic State Model

  • Accounts:
    Two types:

    1. Externally Owned Accounts (EOAs): normal wallets (just balance + nonce).
    2. Contract Accounts: smart contracts (balance + code + storage).

  • Storage:

    • Each contract account has its own persistent key-value store.
    • This storage is part of the world state, kept in the Merkle Patricia Trie.
    • Keys/values are 32-byte slots.

🔹 Solidity Example (your array case)

uint256[] public myArray;

🔹 Storage Mapping in Solidity

  • myArray.length → stored at a fixed slot.
  • Elements (myArray[0], myArray[1], …) → stored at derived slots (using keccak256 hashing).

When your contract runs, the EVM reads/writes these slots in the account’s storage.

🔹 Key Point

  • Yes: In Ethereum/ETC, “storage” is the persistent data space inside contract accounts.
  • EOAs (human wallets): no contract storage, only balance + nonce.
  • All of this lives inside the global state trie, so every node can validate and reproduce the same results.

✅ In short:
Arrays, mappings, and structs in Solidity → compiled into storage slots → stored in the contract account → persisted in the state trie.

🔹 Coinbase Accounts

  • User accounts at Coinbase

    • When you open a Coinbase account, they create a custodial wallet for you.
    • On-chain, this corresponds to an Externally Owned Account (EOA) controlled by Coinbase’s infrastructure, not directly by you.
    • Coinbase holds the private keys, you just interact via their app/API.

  • Contract accounts

    • Coinbase doesn’t create contract accounts for you by default.
    • If you deploy a smart contract, you (or your app) would create that account on Ethereum, not Coinbase.

✅ In short:
Coinbase user wallets are EOAs. They’re custodial EOAs, meaning Coinbase holds the keys. Contract accounts are separate and created only when you deploy smart contracts.

🔹 MetaMask Accounts

  • EOAs only

    • MetaMask generates Externally Owned Accounts (EOAs) for users.
    • You control these via your private key or seed phrase.
    • These EOAs can hold ETH/tokens, sign txs, and interact with smart contracts.

  • Contract accounts

    • MetaMask does not create contract accounts automatically.
    • If you deploy a smart contract using MetaMask, that action creates a new contract account on Ethereum.
    • But the creation comes from your EOA sending a deployment transaction.

✅ In short:
MetaMask = wallet for EOAs.
Contract accounts exist only if you deploy a contract from your EOA.

🔹 Create an Externally Owned Account (EOA)

  • EOAs are just a keypair (private key + address).
  • They are not created on-chain until they send or receive ETH/tokens.
  • Typical API calls:
    • web3.js / ethers.js 
      // web3.js
const account = web3.eth.accounts.create();
console.log(account.address, account.privateKey);
      // ethers.js
const wallet = ethers.Wallet.createRandom();
console.log(wallet.address, wallet.privateKey);
    • JSON-RPC
      • personal_newAccount (if node has the personal API enabled)

🔹 Create a Contract Account

  • Contract accounts are created on-chain when an EOA sends a special transaction with data = compiled bytecode.
  • Typical API calls:
    • JSON-RPC
      • eth_sendTransaction with a data field (no to address)
      {
  "from": "0xYourEOA",
  "data": "0x6080604052...",   // contract bytecode
  "gas": "0x500000"
}
    • web3.js / ethers.js 
      const contract = new web3.eth.Contract(abi);
contract.deploy({ data: bytecode })
  .send({ from: account, gas: 5000000 });
      const factory = new ethers.ContractFactory(abi, bytecode, wallet);
const contract = await factory.deploy();

✅ In short:

  • EOA = keypair → created locally via libraries (accounts.create, Wallet.createRandom, etc.), no transaction required.
  • Contract account = deployed contract → created on-chain via eth_sendTransaction with data = bytecode.

🔹 EOAs and the Ledger

  • An EOA is just a keypair (address + private key).
  • When you generate it locally (MetaMask, ethers.js, Coinbase internal systems), it doesn’t yet exist on-chain.
  • The Ethereum ledger doesn’t pre-store “all possible addresses.”

🔹 How it receives assets

  • Ethereum’s world state (state trie) is a mapping: address → account data.
  • If an address has never been used, it simply isn’t present in the state trie.
  • The moment someone sends ETH/tokens to it, the EL client:
    • Creates a new entry in the state trie for that address.
    • Initializes it with balance (and nonce = 0).

🔹 Key Point

  • You don’t need to “register” an EOA on-chain before receiving assets.
  • The address is deterministically derived from your keypair, so anyone can send to it.
  • The ledger will “activate” the account when a transaction or transfer first touches it.

✅ In short:
An EOA is “off-chain” until first use. Once ETH or a token is sent to it, the execution client creates an entry for it in the global state, and from then on, it’s part of the ledger.

🔹 How Ethereum Addresses Are Derived

  1. Private key
  • A random 256-bit number.
  • Must remain secret (controls the account).
  1. Public key
  • Derived from the private key using Elliptic Curve Cryptography (secp256k1).
  • One-to-one relationship: every private key produces exactly one public key.
  1. Address
  • Take the public key.
  • Hash it with keccak256.
  • Take the last 20 bytes → that’s your Ethereum address.
  • Example: 
    address = keccak256(public_key)[12:]

🔹 Why it’s deterministic

  • Given the same private key → always get the same public key → always get the same address.
  • No central registry is needed.
  • That’s why wallets like MetaMask or Coinbase can generate addresses offline and know they’ll work.

🔹 How others can send to it

  • Once you know the address, you don’t need the private key to send assets there.
  • Anyone can include that address in a transaction’s to field.
  • When the first transfer happens, Ethereum clients add the address to the global state with its new balance.

✅ In short:
An Ethereum address is just a deterministic hash of a keypair. Because it’s predictable and unique, it can receive ETH or tokens even before it appears on-chain.

🔹 Block arrives

  • The EL client receives a new block (with its transactions) from peers.
  • Each transaction has a from, to, value, gas, and optional data.

🔹 Processing transactions

  • For each tx, the client:
    1. Checks sender (from)
    • The account must already exist in the state trie (otherwise tx is invalid).
    1. Checks recipient (to)
    • If to exists → update its balance / run contract code.
    • If to does not exist and it’s not empty code → create a new account entry in the state trie.
      • Example: first time you send ETH to a fresh EOA.

🔹 Updating the global state trie

  • If an address didn’t exist in the trie yet:
    • The client inserts a new entry (balance = value, nonce = 0, code = empty, storage = empty).
  • The state root is recalculated after applying all transactions in the block.
  • The block header includes this new state root, which every node checks to stay in sync.

🔹 Key Point

  • EL clients don’t “pre-know” all addresses.
  • They dynamically add them to the state trie the first time a tx touches them.
  • That’s how a never-before-used EOA can suddenly hold ETH after its first incoming transfer.

✅ In short:
When a block arrives, the EL client processes txs → if a to address isn’t in the trie yet, it creates it on the fly and updates the state accordingly.

🔹 Why an EOA address is unique and deterministic

  • 1 private key → 1 public key → 1 address
    • Private key: random 256-bit number.
    • Public key: derived from private key using elliptic curve multiplication (secp256k1).
    • Address: address = keccak256(public_key)[12:] → last 20 bytes.

🔹 Key implications

  • Deterministic: Same private key always yields the same address.
  • Unique: The probability of two private keys giving the same address is astronomically small.
  • Trustless: Anyone can generate an address offline, no central registry needed.
  • Receivable: Others only need the 20-byte address, not the public or private key, to send ETH/tokens.

✅ In short:
An EOA works because cryptography guarantees a 1-to-1 deterministic mapping from private key → public key → address. That’s why an address can exist “off-chain” and still receive assets the first time it’s referenced in a block.

🔹 Private Key

  • A 256-bit secret number — must be kept hidden.
  • Used for:
    • Signing transactions (ECDSA signatures).
    • Proving ownership of the account (you control the funds).
  • Never shared; only the signature is broadcast.

🔹 Public Key

  • Derived from the private key (via secp256k1 elliptic curve multiplication).
  • Used for:
    • Verifying signatures → nodes confirm that a tx was signed by the right private key.
    • Deriving the address → keccak256(public_key)[12:].
  • Doesn’t need to be kept secret; anyone can know it.

🔹 Address

  • Derived from the public key.
  • Used for:
    • Receiving ETH/tokens.
    • Identifying accounts on-chain.
  • Much shorter (20 bytes) so easier to handle than raw public keys.

✅ In short:

  • Private key = sign.
  • Public key = verify.
  • Address = receive.

🔹 Public Key

  • What it is:

    • Mathematically derived from the private key (via elliptic curve multiplication).
    • A fixed identifier that corresponds to one private key.

  • Purpose:

    • Used to verify signatures created with the private key.
    • Used to derive your address (keccak256(public_key)[12:]).

  • Properties:

    • Can be shared openly.
    • Same every time (doesn’t change).

🔹 Signature

  • What it is:

    • A cryptographic proof generated by applying the private key to some message (e.g., a transaction).
    • In Ethereum, this is an ECDSA signature (r, s, v values).

  • Purpose:

    • Proves that the message/transaction came from the holder of the private key.
    • Allows others to check validity using only the public key.

  • Properties:

    • Different every time, even if the same message is signed (because of randomization in the algorithm).
    • Only valid for the specific message signed.

✅ In short:

  • Public key = a static identifier derived from the private key, used for verification.
  • Signature = a dynamic proof generated with the private key, used to show authenticity of a specific message.

🔹 Step 1 — You create the transaction

  • You fill in:
    • to = your friend’s address
    • value = 1 ETH
    • gas + maxFeePerGas
  • This unsigned transaction is just a piece of data.

🔹 Step 2 — MetaMask uses your private key

  • MetaMask holds your private key (in the browser extension, encrypted with your password).
  • It takes the unsigned tx data and runs ECDSA signing with your private key.
  • Output = transaction + signature (r, s, v).
  • The private key never leaves MetaMask.

🔹 Step 3 — Transaction broadcast

  • The signed transaction is sent to your connected Execution Layer (EL) client (e.g., Infura, Alchemy, or your own Geth).
  • The client gossips it across the Ethereum p2p network (devp2p → eth/66 protocol).

🔹 Step 4 — How the EL verifies

When another EL client receives the tx:

  1. Recover public key from the signature (possible because ECDSA allows key recovery).
  2. Hash public key with keccak256, take last 20 bytes → reconstruct the sender address.
  3. Check:
  • Does the sender exist in the state trie?
  • Does the sender have ≥ 1 ETH + gas fees?
  • Is the nonce correct?
  • Is the signature valid?

If all checks pass → tx is valid and goes to the mempool.

🔹 Step 5 — Block inclusion

  • A validator eventually proposes a block.
  • The EL executes your tx:
    • Deducts 1 ETH + gas from your EOA balance.
    • Increments your nonce.
    • Adds 1 ETH to your friend’s account (creating it in the trie if it didn’t exist yet).

✅ In short:

  • Private key: signs the tx (in MetaMask).
  • Signature: proves authenticity, lets EL recover your public key/address.
  • Public key: never sent directly, only reconstructed from the signature.
  • Execution client: verifies signature + state, then updates balances when block is mined.

🔹 1. Proposer is chosen

  • In Proof-of-Stake, the beacon chain (Consensus Layer) randomly selects a validator to propose the next block.
  • That validator runs both:
    • A Consensus Layer (CL) client (e.g., Lighthouse, Prysm).
    • An Execution Layer (EL) client (e.g., Geth, Nethermind).

🔹 2. EL prepares the payload

  • The validator’s EL client takes pending transactions from its mempool.
  • It executes them in order, applying gas limits and validity checks.
  • Result = execution payload:
    • List of transactions
    • Resulting state root
    • Receipts, logs, etc.

🔹 3. Handshake between EL and CL

  • The EL client passes this execution payload to the validator’s CL client through the Engine API (engine_getPayload, engine_newPayload, etc.).
  • CL client doesn’t execute txs — it just trusts EL for state.

🔹 4. Block is proposed

  • The validator’s CL client wraps the execution payload into a beacon block.
  • Broadcasts the block to other validators on the P2P network.

🔹 5. Other validators verify

  • Peers’ EL clients re-execute the payload transactions to confirm the state root.
  • Their CL clients check consensus rules (signatures, attestations).
  • If all checks pass → block accepted.

✅ In short:

  • The EL client inside the validator’s own node feeds transactions → execution payload → to the CL client.
  • The CL client → proposes the block to the rest of the network.
  • So the tx doesn’t “travel” to some remote staker — the validator is running EL+CL together.

🔹 Normal flow (no MEV-Boost)

  • Each validator runs its own EL client with a mempool.
  • When selected to propose a block, it picks txs from its own mempool to build the block.

🔹 With MEV-Boost

  • Validators outsource block building to external block builders.

  • Flow:

    1. Searchers → send bundles of profitable txs to builders.
    2. Builders → construct candidate full blocks (using their own mempool + bundles).
    3. Builders → submit bids via relays to validators.
    4. Validator (via MEV-Boost middleware) → chooses the most profitable block proposal.

  • The validator’s own EL client doesn’t build the block in this case — it just verifies the block is valid after the builder provides it.

🔹 Key point

  • MEV-Boost does not send txs directly into a validator’s mempool.
  • Instead, it bypasses the validator’s mempool entirely by letting builders deliver ready-made blocks.
  • Validators pick between blocks (auctions), not transactions.

✅ In short:

  • Without MEV-Boost: Validator’s mempool → block.
  • With MEV-Boost: Builder’s mempool/bundles → block → validator.

🔹 Execution Payload (simplified structure)

  • parentHash – Hash of the parent execution block.
  • feeRecipient – Address that receives transaction fees (validator’s chosen withdrawal address).
  • stateRoot – Root of the state trie after applying all included transactions.
  • receiptsRoot – Root of the receipts trie (logs/events for each tx).
  • logsBloom – Bloom filter for quickly searching logs/events.
  • prevRandao – Randomness for the block (from beacon chain).
  • blockNumber – Height of the chain.
  • gasLimit / gasUsed – Gas constraints for the block.
  • timestamp – Unix time of the block.
  • baseFeePerGas – Base fee from EIP-1559.
  • extraData – Arbitrary data (set by proposer/builder).
  • transactions[] – The full list of signed txs included.
  • withdrawals[] – Withdrawals from validator balances (post-Shanghai/Capella).

🔹 Example (simplified JSON)

{
  "parentHash": "0xabc123...",
  "feeRecipient": "0xdef456...",
  "stateRoot": "0x789abc...",
  "receiptsRoot": "0x456def...",
  "logsBloom": "0x00...ff",
  "blockNumber": 1928374,
  "gasLimit": 30000000,
  "gasUsed": 2893472,
  "timestamp": 1694451200,
  "baseFeePerGas": "0x34e62ce00",
  "transactions": [
    "0xf86c820...",
    "0xf87083..."
  ],
  "withdrawals": [
    { "index": 1, "validatorIndex": 12345, "address": "0xaaa...", "amount": 32000000000 }
  ]
}

🔹 Why miners went to Siberia

  • PoW required massive energy, and electricity was the #1 cost.
  • Regions with cheap hydropower (Siberia, Quebec, Iceland, parts of China) became mining hubs.
  • Firms co-located their rigs near power stations to cut costs.

🔹 What happened after The Merge

  • Ethereum (ETH) abandoned PoW completely → GPUs/ASICs for ETH became useless.
  • Some miners tried to:
    • Switch to Ethereum Classic (ETC) or coins like Ravencoin, Ergo.
    • Repurpose GPUs for AI/ML workloads.
    • Sell hardware (big wave of used GPUs hit markets in 2022–23).
  • Specialized ETH ASICs mostly became e-waste.

🔹 Today

  • The ETH PoW mining business is gone.
  • Bitcoin mining still thrives — and cheap electricity hubs are still relevant — but BTC is mined with specialized ASICs, not GPUs.
  • Those Siberian operations that were ETH-only either pivoted to BTC/ETC, sold off, or shut down.

✅ In short:
The “cheap hydropower farm in Siberia” strategy worked in the PoW era. After Ethereum’s Merge, ETH mining ended, so that business disappeared — only BTC and a few smaller PoW coins keep similar setups alive.

🔹 Example of Profitable Transactions to Builders

  • Arbitrage:
    Buy token on Uniswap at 100, sell on Sushiswap at 102 → profit from price difference.
  • Liquidations:
    On Aave or Maker, liquidate an undercollateralized loan → get a liquidation bonus.
  • Sandwich attack:
    Detect a large buy order in mempool → place your buy just before, and sell just after, profiting from slippage.
  • Bundle:
    Searcher can package multiple txs together (buy + sell) to guarantee atomic profit if block includes both.

Builders receive these bundles and create blocks with maximum value for validators.

🔹 Who is a Searcher?

  • Searcher = profit seeker.
  • They run bots to scan the mempool or private relays for opportunities.
  • Use custom simulation engines to test “what if my tx went here?” scenarios.
  • Submit bundles of profitable txs to builders (via Flashbots or other relays).
  • Compete against other searchers → whoever pays the highest tips to validators usually wins.

✅ In short:

  • Searcher = trader/algorithm/bot that finds and bundles profitable opportunities.
  • Builder = block constructor who takes txs (including from searchers) and assembles the most profitable block.
  • Together they feed the MEV auction that validators pick from.

🔹 Collateralized Lending (Aave / Maker)

  • User deposits collateral (e.g., 10 ETH) and borrows stablecoins (e.g., 10,000 DAI).
  • Protocol requires a collateral ratio (e.g., 150%).

🔹 When the loan goes underwater

  • If ETH price drops, collateral may no longer meet the ratio.
  • Example: 10 ETH @ $2,000 = $20,000 collateral → ratio = 200%.
  • If ETH falls to $1,200 → $12,000 collateral, ratio = 120% (below 150%).
  • Loan is now undercollateralized.

🔹 Liquidation process

  1. Protocol marks the position as liquidatable.
  2. Searcher (liquidator) sends a liquidation transaction.
  • Repays part/all of the borrower’s debt on their behalf.
  1. In return:
  • Liquidator seizes borrower’s collateral at a discount (e.g., 5–10%).
  • That discount = liquidation bonus, pure profit for the liquidator.

🔹 Why it’s profitable

  • Liquidators can instantly resell the collateral on DEXs.
  • The “bonus” ensures bots/searchers race to liquidate risky positions.

✅ In short:
Liquidations = buying collateral at a discount by paying off someone’s bad loan.
Searchers/bots compete to grab these chances for a guaranteed profit.

🔹 Case: Liquidation on Aave / Maker

  • Borrower’s position falls below collateral ratio.
  • Liquidator repays the borrower’s debt (partially or fully).
  • In return, liquidator gets the borrower’s collateral + a small bonus.

🔹 Does Aave/Maker lose money?

  • No, normally they don’t.

    • The debt is repaid (by the liquidator).
    • The seized collateral covers the debt + the liquidation bonus.
    • Protocol remains solvent.

  • When risk appears:

    • If the market moves too fast (e.g., ETH price crashes suddenly), collateral value might fall below debt + bonus.
    • In such cases, protocol’s insurance fund (e.g., Aave Safety Module, Maker’s Surplus Buffer) absorbs the shortfall.

🔹 Who bears the loss?

  • Normal liquidation: borrower loses collateral, liquidator profits, protocol safe.
  • Extreme crash: protocol’s backstop funds or governance tokens (AAVE/MKR) may be used to cover deficit.

✅ In short:

  • In regular conditions → Aave/Maker do not lose money in liquidations.
  • In extreme volatility → losses are socialized via insurance/backstop mechanisms.

🔹 Aave

  • All core contracts (LendingPool, Incentives, Governance, etc.) are deployed on Ethereum.
  • Source code is published and verified on Etherscan.
  • Repo: github.com/aave/protocol-v2 (and v3).
  • Governance decisions (risk parameters, asset listings) are made by AAVE token holders through on-chain governance.

🔹 MakerDAO

  • Maker Protocol contracts (Vaults, Collateral, DAI Stablecoin, Liquidations) are also fully on-chain.
  • Verified on Etherscan.
  • Repo: github.com/makerdao.
  • Governance (like stability fees, collateral ratios) decided by MKR token holders via public governance votes.

🔹 Why this matters

  • Because contracts are public + immutable once deployed, users and searchers/liquidators can trust:
    • How collateralization is calculated.
    • How liquidations happen.
    • How governance parameters are applied.
  • Protocol transparency = stronger trust, no hidden rules.

✅ In short:
Yes — Aave and Maker publish their smart contracts openly, and loan governance (risk params, fees, collateral) is enforced by on-chain code plus token-holder governance.

🔹 Ethereum (L1)

  • Base blockchain network.
  • Provides security, consensus, and settlement.
  • Hosts smart contracts for apps like Aave, Maker, Uniswap, etc.

🔹 Aave

  • A lending protocol deployed as smart contracts on Ethereum (and also on some L2s like Polygon, Arbitrum, Optimism).
  • Not its own chain — it lives on Ethereum or L2s.

🔹 MakerDAO

  • Protocol behind the DAI stablecoin.
  • Runs entirely on Ethereum smart contracts.
  • Uses governance via MKR token to set parameters.
  • Also not its own chain.

✅ In short:

  • Ethereum = L1 blockchain.
  • Aave & MakerDAO = applications/protocols built on Ethereum L1 (and some L2s).
  • They depend on Ethereum’s security, not their own consensus.

🔹 What is Base?

  • A Layer 2 blockchain built by Coinbase.
  • Uses the OP Stack (same tech as Optimism).
  • Secures itself by posting data/transactions back to Ethereum (L1).

🔹 Why it exists

  • Cheaper & faster transactions than Ethereum mainnet.
  • Fully compatible with the Ethereum Virtual Machine (EVM).
  • Tightly integrated with Coinbase products → easy on/off ramps.

🔹 Key traits

  • Not an L1 → it inherits security from Ethereum.
  • Rollup: executes transactions off-chain, then batches them to Ethereum.
  • Ecosystem: DeFi, NFTs, on-chain apps — same as Ethereum, but lower gas.

✅ In short:
Base = Coinbase’s Ethereum Layer 2 (built with Optimism tech).
It’s not its own L1 like Ethereum or Solana — it’s an L2 rollup that depends on Ethereum for final security.

🔹 Sequencers (in L2s like Base, Arbitrum, Optimism)

  • Role: order transactions and create L2 blocks.
  • They do not run MEV auctions like Ethereum validators.
  • They send compressed transaction data back to Ethereum (L1) for finality.
  • Today: centralized (often a single sequencer per rollup, run by the project team).
  • Future: roadmap to decentralize sequencing and enable shared MEV auctions.

🔹 MEV Relays / Validators (Ethereum L1)

  • Validators: chosen by Ethereum PoS to propose blocks.
  • MEV relays: deliver block bundles (via MEV-Boost) to validators.
  • This happens only on Ethereum L1, not inside Base/Arbitrum/Optimism (yet).

🔹 Key Difference

  • Sequencer = transaction orderer in an L2.
  • Validator/Relay = transaction/bundle orderer in Ethereum L1 MEV auctions.
  • Base’s sequencer (run by Coinbase) decides tx order within Base, but Base still posts the results to Ethereum, where L1 validators enforce finality.

✅ In short:
Coinbase’s Base sequencers are not MEV relays or validators. They are L2 ordering nodes. Ethereum L1 validators (with MEV relays) still decide the final ordering at the base layer.

🔹 L2 Landscape (Explanation)

  • Polygon

    • PoS sidechain (separate validators), now expanding with zkEVM.
    • ✅ Strength: broad ecosystem, enterprise adoption.
    • ❌ Weakness: PoS chain ≠ Ethereum-level security.

  • Arbitrum

    • Largest Optimistic Rollup by adoption.
    • ✅ Strength: deep DeFi liquidity (GMX, Radiant, etc.).
    • ❌ Weakness: centralized sequencer, fraud proofs not yet fully live.

  • Optimism

    • Pioneer Optimistic Rollup, builder of the OP Stack.
    • ✅ Strength: “Superchain” ecosystem effect.
    • ❌ Weakness: still centralized sequencing.

  • Base (Coinbase L2)

    • Built with OP Stack, retail-friendly, Coinbase integrated.
    • ✅ Strength: rapid adoption via Coinbase funnel.
    • ❌ Weakness: limited decentralization, sequencer run by Coinbase.

🔹 TVL Ranking (Sept 2025, DeFiLlama)

Rank Network TVL (approx)
1 Arbitrum ~$14.2B
2 Base ~$9.1B
3 Optimism ~$7.8B
4 Polygon ~$5.3B

✅ In short:

  • Arbitrum leads in liquidity.
  • Base has surged thanks to Coinbase funnel.
  • Optimism strong due to OP Stack adoption.
  • Polygon relevant, but trails Ethereum-native L2s in TVL.

🔹 Why integrate with L2s?

  1. Lower Transaction Costs
  • L1 gas fees can spike to $20–$100+ per tx.
  • On L2s, fees are typically a few cents → better UX for users.
  1. Higher Throughput
  • L1 can handle ~15–20 TPS.
  • L2s batch txs → effective throughput is much higher.
  • Suitable for gaming, micro-payments, NFT minting, etc.
  1. User Growth
  • Many retail users (especially from Coinbase via Base) onboard directly to L2s.
  • Being on L2s = access to this user base.
  1. Liquidity & Ecosystem
  • Arbitrum, Optimism, Base, Polygon have billions in TVL and active DeFi/NFT communities.
  • Integrating gives exposure to existing liquidity pools and partnerships.
  1. Still Secured by Ethereum
  • Unlike deploying on a non-Ethereum chain (e.g., Solana), L2s inherit Ethereum’s security.
  • Lower risk for your users’ funds.
  1. Future-Proofing
  • Ethereum’s roadmap (Danksharding, EIP-4844) is designed around L2s.
  • Deploying on L2s now = aligning with where the ecosystem is heading.

✅ In short:
You’d integrate with L2s for cheaper fees, faster transactions, more users, and access to growing ecosystems, all while keeping Ethereum-level security.

🔹 Ethereum’s Roadmap Impact on L2s

EIP-4844 (Proto-Danksharding, live in 2024)

  • Introduces “blobs” → cheap data space in Ethereum blocks.
  • L2s currently post calldata to Ethereum (expensive).
  • With blobs → data posting costs drop 10–100x.
  • Tx fees on L2s become a few cents or less → micropayments, mass adoption practical.

Danksharding (future, full version)

  • Scales blobs massively (more data per block).
  • Supports hundreds of L2s running cheaply in parallel.
  • Ethereum L1 = data availability layer, all L2s inherit security.

✅ Impact:

  • Arbitrum, Optimism, Base, Polygon zkEVM → all get cheaper fees + scalability.
  • Competition moves from fees → to ecosystem, liquidity, and user funnels.

🔹 Can you deploy Solidity contracts directly on L2?

Yes.

  • L2s (Arbitrum, Optimism, Base, Polygon zkEVM) are EVM-compatible.
  • Write Solidity the same as on L1.
  • Deploy via the L2 RPC endpoint.

Example (ethers.js)

const { ethers } = require("ethers");

// Connect to Base (L2) instead of Ethereum L1
const provider = new ethers.JsonRpcProvider("https://mainnet.base.org");
const wallet = new ethers.Wallet(PRIVATE_KEY, provider);

// Standard Solidity contract deploy
const factory = new ethers.ContractFactory(abi, bytecode, wallet);
const contract = await factory.deploy();
console.log("Deployed to:", contract.target);

🔹 Current Trends in Ethereum (2025)

EIPs / Mainnet Upgrades

  • Pectra upgrade (May 2025): ~11 EIPs, including:
    • Smart EOAs (EIP-7702)
    • Optimized validator signature schemes
    • Blob parameterization (scaling data availability)
    • Historical block hash access
  • Continued roll-out of EIP-4844 (blobs) → cheaper L2 data posting.
  • More efficient cryptography (BLS precompiles, lighter sigs).
  • Growing focus on account abstraction for better wallet UX.

L2 / Scaling Trends

  • L2s (Base, Arbitrum, Optimism, Polygon zkEVM) taking a bigger share of tx volume.
  • Post-Dencun/Pectra upgrades → L2 fees down 90–98%.
  • Experiments with gasless L2s and subsidized fee models.
  • Rising TVL and app ecosystems moving toward L2-first deployment.

🔹 ETH on L1 vs L2

  • ETH on L1 (mainnet): Native ETH, universally recognized.
  • ETH on L2 (Arbitrum, Optimism, Base, Polygon zkEVM):
    • Technically an IOU / representation of ETH bridged from L1.
    • It exists in the L2’s state, not automatically on L1.

🔹 Receiving ETH on an L2 wallet

  • If someone sends you 1 ETH on Base, it lives in the Base network’s state.
  • Your wallet address is the same, but balances are tracked separately by each chain.
  • It will not automatically appear on mainnet — only on Base.

🔹 Moving ETH between L1 and L2

  • To reflect ETH on both sides, you must use a bridge:
    • Deposit: lock ETH on Ethereum → mint ETH on L2.
    • Withdraw: burn/release ETH on L2 → unlock ETH on Ethereum.
  • Bridges are built into each rollup (Arbitrum bridge, Optimism gateway, Base bridge, etc.).

✅ In short:
ETH on an L2 wallet does not show up on mainnet by default.
You need to bridge it back to L1 if you want mainnet ETH.

🔹 Why the trie keeps growing

  • Every new account, contract, or storage variable adds entries to the state trie.
  • Even if some contracts are inactive, their state often remains.
  • Over time → trie = bigger and more complex.

🔹 Hardware impact on full nodes

  1. Disk (SSD)
  • State and history are stored in LevelDB/RocksDB.
  • The larger the trie, the bigger the on-disk database.
  • Today: hundreds of GBs (state + history).
  • Archival nodes (with all historical states) = several terabytes.
  1. RAM
  • Node must cache part of the trie for performance.
  • As trie size grows, more RAM helps with fast lookups.
  • Typical full node: 16–32 GB RAM recommended for healthy performance.
  1. CPU
  • Needed for hashing (keccak256) and verifying blocks.
  • Bigger trie = more hashing and lookups per block.

🔹 Mitigations

  • Pruning: Removes old historical state, keeps only latest.
  • Snapshots: Speeds up state access instead of walking the trie every time.
  • Stateless roadmap: Ethereum research aims to reduce how much state each node must hold.
  • Verkle tries (future): More efficient successor to the Merkle Patricia Trie.

✅ In short:
Yes — as the trie grows, disk and RAM needs go up for full nodes. That’s why Ethereum clients recommend SSDs and large memory. Future upgrades (Verkle tries, pruning, statelessness) aim to keep node requirements manageable.

🔹 Full Node vs Archival Node (Ethereum)

Full Node

  • Stores:
    • Current state (balances, storage, contract code).
    • Recent block history (usually a few thousand blocks).
  • Deletes/prunes:
    • Old historical state (past account balances, storage snapshots).
  • Purpose:
    • Can validate all new transactions and blocks.
    • Keeps network secure.
    • Enough for running wallets, dApps, validators, and explorers that only need latest state.
  • Storage size (2025): ~500–800 GB on SSD.

Archival Node

  • Stores:
    • Everything a full node does plus all historical states (every balance, storage slot, and contract state at every block since genesis).
  • Never prunes: keeps the entire chain history.
  • Purpose:
    • For explorers (like Etherscan), analytics, research.
    • Useful if you want to query: “What was Alice’s balance at block 7,000,000?”
    • Not needed for normal use.
  • Storage size (2025): 15–20+ TB (grows constantly).

Key Difference

  • Full node: Only latest state → efficient, enough to participate in consensus.
  • Archival node: All historical states → massive storage, mainly for research/exploration.

✅ In short:

  • Full node = lean, validates current chain, recommended for most users/validators.
  • Archival node = full history of everything, needed only for explorers, researchers, or analytics platforms.

🔹 Lite Nodes on L2s

1. Optimistic Rollups (Arbitrum, Optimism, Base)

  • Sequencer: orders txs and posts compressed data (calldata/blobs) to Ethereum L1.
  • Lite node on L2:
    • Doesn’t hold full state.
    • Verifies L2 block headers and proofs of data availability.
    • For deeper queries (balances, logs), it asks a full L2 node.
  • Security: ultimately backed by Ethereum full nodes, since rollups post data to L1.

2. zk-Rollups (Polygon zkEVM, zkSync, StarkNet)

  • Post validity proofs (zk-SNARKs) to L1.
  • Lite node on L2:
    • Can cheaply verify proofs without replaying every transaction.
    • Requires very little storage or computation.
  • This makes zk-rollups especially friendly for light clients.

3. Practical Reality (2025)

  • Most users (e.g., MetaMask, Coinbase Wallet) don’t run full or lite nodes.
  • They connect to RPC providers (Infura, Alchemy, QuickNode, etc.).
  • Research and some projects are working on trust-minimized light clients for L2s, but adoption is still early.

✅ In short:
Yes — L2s can have lite nodes:

  • Optimistic rollups → light clients that verify headers + fraud-proof system.
  • zk-rollups → even better, since validity proofs allow cheap verification.
    But today, most apps just connect to RPC providers instead of running a lite node.

🔹 What are zk-Rollups?

  • A Layer 2 scaling solution that batches many transactions off-chain and posts:

    1. Compressed transaction data → to Ethereum L1 (for availability).
    2. A validity proof (zk-SNARK/STARK) → to Ethereum L1 (for correctness).

  • “zk” = zero-knowledge → proofs show a statement is true without revealing all details.

🔹 How it works (step by step)

  1. Users send transactions → sequencer/rollup node collects them.
  2. Rollup executes all txs off-chain.
  3. Instead of sending every computation to L1, it generates a cryptographic proof that all txs were valid.
  4. Proof + minimal data are submitted to Ethereum L1.
  5. Ethereum full nodes verify the proof very efficiently (milliseconds), without re-running all txs.

🔹 Why it’s powerful

  • Scalability: Thousands of txs compressed into one proof → huge throughput.
  • Cheap verification: Ethereum only checks the proof, not every tx.
  • Fast finality: Once proof is accepted on L1, txs are considered final.
  • Security: Inherits Ethereum L1 security — if the proof checks out, txs are valid.

🔹 Examples

  • Polygon zkEVM → aims for full EVM compatibility using zk-proofs.
  • zkSync Era → zk-rollup with a focus on developer-friendly tooling.
  • StarkNet → zk-rollup using STARKs (different proof system, more scalable).

🔹 Is it only an L2 feature?

  • Mostly yes today: zk-rollups are used as Ethereum L2s.
  • But the concept is more general:
    • L1 blockchains themselves could adopt zk-proofs internally (e.g., zk-powered consensus).
    • Some projects are exploring zk-L1s (chains that use zk-proofs as their native consensus).
    • Example: Mina Protocol markets itself as a “zk-L1.”

✅ In short:

  • zk-Rollups = Ethereum L2 feature that scales by posting validity proofs to L1.
  • Not limited to L2s → zk-proofs can also be used at the L1 level, but Ethereum currently applies them in L2s.

🔹 Does Geth check zk-proofs in block payloads?

  • No.
  • Ethereum L1 (Geth, Nethermind, Besu, etc.) does not natively handle zk-proofs inside execution payloads.
  • Ethereum still executes its own transactions normally (every tx is re-run by every full node).

🔹 Where zk-proofs live

  • zk-rollups (Polygon zkEVM, zkSync, StarkNet) are smart contracts deployed on Ethereum L1.
  • These contracts:
    • Accept compressed rollup transaction data + zk-proof.
    • Verify the proof inside the contract (using precompiles for zk-SNARK/STARK verification).
    • Update the rollup’s state root if valid.

🔹 What Geth actually does

  • Geth just sees: “Oh, here’s a transaction calling the rollup contract.”
  • It runs the contract code like any other tx.
  • The contract itself runs the zk-verification logic.
  • Geth doesn’t need to “know about zk-rollups” — it just executes EVM code.

🔹 Why it’s not hardcoded

  • Ethereum is general-purpose:
    • zk-rollups, optimistic rollups, DeFi apps, NFTs → all are just smart contracts.
  • The protocol doesn’t need special zk-logic at the client level.
  • Instead, zk-rollups embed verification logic in their contracts.

✅ In short:

  • Geth is not hardcoded to check for zk-proofs in block payloads.
  • zk-rollups are implemented as smart contracts on Ethereum.
  • Geth just executes those contracts — the zk-proof verification happens inside the rollup contract.

🔹 Gas Guzzlers (Top Contracts by Gas Consumption)

1. Tether: USDT Stablecoin

  • Fees last 3hrs: ~$4,887 (1.08 ETH)
  • Fees last 24hrs: ~$55,731 (12.30 ETH)
  • % of gas used: ~6–7% of all Ethereum gas.
  • Why? USDT is the most traded stablecoin, so transfers and approvals eat up lots of gas.

2. Uniswap V2: Router 2

  • Fees last 3hrs: ~$1,153 (0.25 ETH)
  • Fees last 24hrs: ~$15,133 (3.34 ETH)
  • % of gas used: ~3.2%.
  • Why? Users still swap tokens via older Uniswap V2 contracts. Each swap = multiple ERC20 transfers + liquidity pool logic.

3. Circle: USDC Token

  • Fees last 3hrs: ~$2,303 (0.51 ETH)
  • Fees last 24hrs: ~$28,244 (6.23 ETH)
  • % of gas used: ~3.7%.
  • Why? Like USDT, USDC is a top stablecoin. Heavy daily use for DeFi, trading, payments.

4. Uniswap V4: Universal Router

  • Fees last 3hrs: ~$1,498 (0.33 ETH)
  • Fees last 24hrs: ~$16,520 (3.65 ETH)
  • % of gas used: ~2%.
  • Why? The new Uniswap V4 router that aggregates liquidity across pools. Becoming more active as traders migrate.

🔹 What this means

  • Stablecoins (USDT, USDC) + DeFi protocols (Uniswap) dominate Ethereum gas usage.
  • High gas usage = they are the most actively used contracts.
  • When gas prices spike, it’s often due to heavy demand from swaps and stablecoin transfers.

✅ In short:

  • USDT & USDC: heavy gas from constant transfers.
  • Uniswap (V2 & V4): heavy gas from token swaps.
  • Together, these account for 10%+ of Ethereum’s gas use daily.
Rank Contract / dApp What it is
1 Tether: USDT Stablecoin ERC-20 stablecoin pegged to USD. Most traded token, heavy gas from transfers.
2 Uniswap V2: Router 2 Routing contract for swaps/liquidity in Uniswap V2. Still widely used.
3 Circle: USDC Token ERC-20 stablecoin from Circle, pegged to USD. Heavy daily transfers.
4 Uniswap V4: Universal Router Latest Uniswap router, aggregates liquidity across pools. Growing adoption.
5 OKX: DEX Router Router for OKX’s on-chain swap/DEX service.
6 MetaMask: Swap Router Contract used by MetaMask’s built-in swap feature.
7 0x: Allowance Holder Utility contract in 0x protocol, manages token approvals/allowances.
8 Pendle: RouterV4 Router for Pendle Finance (yield trading protocol).
9 Banana Gun: Router 2 Bot-driven trading app/router for sniping tokens quickly.
10 Fake_Phishing1341503 Flagged phishing contract — not a real dApp, marked by Etherscan as scam.

What it is

  • Part of the 0x Protocol, a popular decentralized exchange (DEX) infrastructure.
  • It’s a smart contract that manages token allowances for traders using 0x.

Why it exists

  • In Ethereum, before a smart contract can move your ERC-20 tokens, you must call approve(spender, amount).
  • For DEX aggregators (like 0x), users would otherwise have to approve each swap separately.
  • The Allowance Holder solves this by:
    • Letting you grant 0x a token allowance once.
    • Reusing that approval across many trades.

How it works (step by step)

  1. User approves 0x Allowance Holder contract to spend, e.g., 1000 USDC.
  2. When trading, the 0x exchange contract calls the Allowance Holder to move tokens on behalf of the user.
  3. The Allowance Holder transfers tokens into the DEX pool or to another trader.

Benefits

  • Gas efficiency: fewer repeated approvals.
  • User convenience: one approval unlocks many trades.
  • Security: tokens only move within the 0x system; revoking approval stops it.

Risks

  • Like any approval system, if the Allowance Holder contract (or 0x protocol) were exploited, approved tokens could be at risk.
  • Best practice: approve only what you need or revoke allowances later.

✅ In short:
The 0x Allowance Holder is a helper contract that manages ERC-20 token approvals so users don’t have to constantly re-approve tokens for every 0x trade. It’s about efficiency + UX.

🔹 Does Etherscan need a Full Node or an Archival Node?

Full Node

  • Stores: latest state + recent blocks.
  • Can tell you:
    • Current balances, token transfers, contract calls.
    • Gas used in the latest txs/blocks.
  • Cannot tell you:
    • Historical state at an arbitrary old block (e.g., Alice’s balance at block 7,000,000).

Archival Node

  • Stores: every historical state since genesis.
  • Can answer deep history queries like:
    • "What was Uniswap Router gas usage in 2021?"
    • "What was balance/allowance of this address 2 years ago?"

What "Top 50 Gas Guzzlers" needs

  • The dashboard shows gas usage for the last 3 hours / 24 hours.
  • That only requires a full node, since it just tracks recent transactions.
  • Etherscan does run archival nodes too, but mostly for things like:
    • Historical charts going back years.
    • Showing balances at any past block.
    • Time-travel debugging.

✅ Answer:
For Top Gas Guzzlers (last 3h / 24h) → full node is enough.
For historical gas analytics (weeks, months, years) → they rely on archival nodes.

🔹 Gas Spenders (Top 50 EOAs Paying Gas)

1. Fake_Phishing1338353

  • Spent ~$5,216 in last 24h (1.10 ETH).
  • Likely flagged as a malicious / scam account by Etherscan.
  • Shows scammers/phishers still pay significant gas to operate bots/contracts.

2. Coinbase: Deposit

  • Spent ~$10,393 in last 24h (2.20 ETH).
  • This is Coinbase’s deposit account → processes thousands of user transfers daily, hence high gas.

3. Fake_Phishing1259784

  • Another phishing account flagged by Etherscan.
  • $3,241 (0.69 ETH) in gas last 24h.

4. jaredfromsubway

  • Famous MEV bot operator.
  • $64,244 (13.60 ETH) spent in last 24h.
  • Runs sandwich attacks / arbitrage strategies, which burn huge gas but earn higher profits.

5–7. More Fake_Phishing accounts

  • Each flagged phishing wallet, still actively sending txs.
  • Spent $2,600–$3,300 in gas fees over 24h.

🔹 Key Insights

  • Exchanges (like Coinbase) spend gas to process massive user inflows/outflows.
  • MEV bots (e.g. jaredfromsubway) spend large gas amounts to front-run and capture profit.
  • Phishing / scam accounts spend gas too — proof that even malicious activity pays Ethereum network fees.

✅ In short:
This dashboard highlights which EOAs (not contracts) are paying the most gas fees. It’s dominated by:

  • Legit services (Coinbase),
  • MEV bot operators,
  • and flagged malicious actors (phishing wallets).

🔹 Gas Guzzlers vs Gas Spenders

Category What it means Who appears here Example from screenshots
Gas Guzzlers Smart contracts / accounts that consume the most gas when executed. Contracts like stablecoins, DEX routers, DeFi protocols. Tether (USDT), Uniswap Router, Circle (USDC).
Gas Spenders Externally Owned Accounts (EOAs) that pay the most ETH in gas fees. Users, exchanges, bots, or attackers sending many transactions. Coinbase Deposit account, MEV bot jaredfromsubway, phishing wallets.

✅ In short:

  • Guzzlers = which contracts are heavy on gas usage.
  • Spenders = which EOAs are footing the bill for gas.
Upgrade Name Block Number Date What It Changed / Why It Mattered
Homestead ~1,150,000 March 14, 2016 First major stable upgrade: improved stability, added EVM opcodes, removed centralised features. oai_citation:0‡RockX
DAO Fork ~1,920,000 July 20, 2016 Emergency fork after The DAO hack to restore stolen ETH; created Ethereum Classic. oai_citation:1‡RockX
Tangerine Whistle (EIP-150) ~2,463,000 October 18, 2016 Mitigated DoS attack vectors by adjusting gas costs. oai_citation:2‡spydra.app
Spurious Dragon ~2,675,000 November 22, 2016 More DoS mitigations, state cleaning, addressing vulnerabilities. oai_citation:3‡spydra.app
Byzantium ~4,370,000 October 16, 2017 Introduced zk-SNARKs, REVERT opcode, reduced block rewards; many performance/security EIPs. oai_citation:4‡spydra.app
Constantinople / Petersburg ~7,280,000 February 28, 2019 Gas optimizations, delays to difficulty bomb, added CREATE2. oai_citation:5‡RockX
Istanbul ~9,069,000 December 8, 2019 Further gas changes and performance improvements. oai_citation:6‡ethereum.org
Berlin ~12,244,000 April 15, 2021 Added new transaction types, more gas cost tweaks. oai_citation:7‡spydra.app
London ~12,965,000 August 5, 2021 Introduced EIP-1559: base fee burning, changed fee structure. oai_citation:8‡ethereum.org
Arrow Glacier ~13,773,000 December 9, 2021 Difficulty bomb delay. oai_citation:9‡spydra.app
Gray Glacier ~15,050,000 June 30, 2022 Last delay before the Merge. oai_citation:10‡ethereum.org
Paris / The Merge ~15,537,393 September 15, 2022 Transition from Proof-of-Work to Proof-of-Stake. oai_citation:11‡ethereum.org
Shanghai / Capella ~17,034,871 April 12, 2023 Enabled staking withdrawals; technical performance improvements. oai_citation:12‡ethereum.org
Cancun / Dencun (EIP-4844) ~19,426,587 March 13, 2024 Introduced blobs / proto-Danksharding, major scaling improvements for rollups. oai_citation:13‡ethereum.org
Pectra (Prague-Electra) ~22,431,084 May 7, 2025 Account abstraction, staking improvements, better user / node operator features. oai_citation:14‡ethereum.org

🔹 More Details: Ethereum Pectra Upgrade

Here are deeper details about Ethereum’s Pectra upgrade (Prague + Electra), what’s included, why it matters. Based on recent sources.

📅 Basic Facts

⚙ Key EIPs in Pectra & Their Effects

EIP What It Does Practical Impact
EIP-7702 (Smart EOAs / Account Abstraction for EOAs) Lets regular user wallets (EOAs) temporarily attach code and behave like a smart contract for a transaction. oai_citation:3‡Alchemy Enables batching, gas-sponsorship, more flexible UX without needing a full smart wallet setup. Some contract checks (like EXTCODESIZE == 0) might need adjusting. oai_citation:4‡Alchemy
EIP-7251 (Max Effective Balance Increase) Increases the maximum stake a validator can earn rewards on from 32 ETH up to 2,048 ETH. oai_citation:5‡Datawallet Large validators or staking services can consolidate/trust fewer validators, reduce overhead. oai_citation:6‡Kraken
EIP-7002 Allows execution layer triggered withdrawals (validators can initiate exits directly) oai_citation:7‡Datawallet More control/flexibility for validators and staking services. oai_citation:8‡Kraken
EIP-6110 Validator deposit supply / onboarding modifications (making validator activation smoother) oai_citation:9‡Kraken Reduces delays for validators; makes staking more efficient. oai_citation:10‡Crypto APIs
EIP-7691 & related rollup/data availability EIPs Increases “blob” capacity per block; adjusts “blob vs calldata” cost dynamics; optimizations for data posting. oai_citation:11‡Alchemy Lower costs for Layer-2 rollups, better network scalability, more predictable fee behavior. oai_citation:12‡Alchemy
EIP-2537 BLS12-381 curve precompile support (faster signature ops) oai_citation:13‡Kraken Helps proofs, zk-systems, validators, consensus-relevant cryptography to be more efficient. oai_citation:14‡Kraken
EIP-2935 Store historical block hashes in state so contracts/light clients can access past hash values more easily. oai_citation:15‡Kraken Improves light client design, randomness, contract logic that needs past block hashes. oai_citation:16‡Kraken

🔍 Impacts & Considerations

  • For developers / dApps:

    • Contract logic relying on assumptions about EOAs vs contract accounts may break (because EOAs can have “code” under certain conditions under EIP-7702). oai_citation:17‡Alchemy
    • Gas-cost profiles may shift (especially around calldata vs blob usage). Optimizing for blobs becomes more important.

  • For users / wallets:

    • More UX improvements: batch transactions, sponsored gas, etc. oai_citation:18‡Alchemy
    • You might see new transaction types in wallets.

  • For validators / staking infrastructure:

    • Can stake more per validator (MaxEB).
    • More efficient onboarding / exit.
    • Possibly fewer nodes needed if large operators leverage higher stake.

  • Network scaling:

    • Blobs capacity increase helps Layer-2 solutions.
    • Historical data access helps light clients / certain contracts.

✅ In short: Pectra is a big upgrade that improves staking flexibility, wallet/user experience, rollup throughput, and protocol efficiency. It doesn’t overhaul Ethereum, but adds several foundational features to enable future scaling.

🧩 What is EigenPhi?

EigenPhi is a blockchain analytics platform specializing in MEV (Maximal Extractable Value) and DeFi transaction flow analysis.

🔹 What EigenPhi Does

  • Tracks MEV activity → front-running, sandwich attacks, arbitrage bundles.
  • Labels MEV-related blocks and transactions in explorers (like in your screenshot).
  • Provides dashboards & APIs for researchers, traders, and protocols to understand:
    • Who the MEV searchers are
    • How much profit they extract
    • How blocks are ordered (MEV relays, private orderflow)
  • Helps identify toxic MEV (hurting regular users) vs. benign MEV (like arbitrage stabilizing prices).

🔹 In Your Screenshot

  • MEV Block → This block contains transactions flagged as MEV-related.
  • EigenPhi → The label is provided by EigenPhi’s classification engine.

✅ In short:
EigenPhi = a research/analytics firm that analyzes Ethereum & DeFi MEV, and provides block explorers with MEV labels.

🔑 Protocol Categories Explained

🌉 Bridges

  • Connect different blockchains.
  • Move assets between chains (e.g., ETH → wrapped ETH on Polygon).
  • Examples: Wormhole, Arbitrum bridge, Polygon bridge.

🔮 Oracles

  • Feed real-world data into blockchains.
  • Smart contracts can’t access external data by themselves.
  • Used for prices, weather, sports results, etc.
  • Examples: Chainlink, Band Protocol.

💸 DeFi (Decentralized Finance)

  • On-chain financial applications: lending, borrowing, trading, yield farming.
  • Replace banks/exchanges with smart contracts.
  • Examples: Aave, Uniswap, Curve.

💧 Liquid Staking

  • Stake tokens but keep liquidity via a “receipt token” (e.g., stETH, rETH).
  • Lets you earn staking rewards and use your assets in DeFi.
  • Examples: Lido, Rocket Pool.

✅ In short:

  • Bridges = move tokens between chains.
  • Oracles = bring outside data in.
  • DeFi = on-chain finance.
  • Liquid Staking = stake + keep liquidity.

🔮 Oracle Data on Ethereum

1. Chainlink

Chainlink provides a wide range of on-chain data feeds:

  • Price Feeds
    • Crypto: ETH/USD, BTC/USD, etc.
    • FX: EUR/USD, JPY/USD, etc.
    • Commodities: Gold, Silver.
    • Stablecoins: USDT/USD, DAI/USD.
  • Proof of Reserves
    • Verifies collateral for stablecoins (e.g., USDC).
  • VRF (Verifiable Randomness Function)
    • Tamper-proof random numbers for games, lotteries.
  • Automation (Keepers)
    • Time-based or condition-based triggers.
  • Cross-Chain Interoperability (CCIP)
    • Messaging & data transfer between blockchains.

2. Band Protocol

Band Protocol focuses on cross-chain and custom data:

  • Price Feeds
    • Crypto: BTC, ETH, SOL, etc.
    • Fiat: USD, EUR, JPY.
    • Commodities: Gold, Oil.
  • Custom Data Feeds
    • Sports results (for prediction markets).
    • Weather data (for insurance).
    • On-demand APIs (developers can request specific external data).

✅ In Short

  • Chainlink → strongest in DeFi price feeds, randomness (VRF), automation, cross-chain messaging.
  • Band Protocol → strong in custom or on-demand APIs, cross-chain integration (Cosmos + Ethereum).

🌉 Cross-Chain & Cosmos Explained

🔗 Chainlink CCIP (Cross-Chain Interoperability Protocol)

  • What it is: A protocol by Chainlink for sending messages, tokens, and data across blockchains.
  • Why it matters:
    • Blockchains are siloed — ETH, Solana, Avalanche can’t natively talk to each other.
    • CCIP provides a secure, standardized way to connect them.
  • Use cases:
    • Move stablecoins from Ethereum → Avalanche.
    • Trigger a contract on Polygon when something happens on Ethereum.
    • Cross-chain DeFi (e.g., collateral on ETH, loan on Arbitrum).

👉 CCIP = an “internet protocol for blockchains.”

⚙️ Cosmos SDK

  • What it is: A modular framework for building blockchains, written in Go.
  • Features / Modules:
    • Accounts & Tokens
    • Governance
    • Staking & Validators
    • IBC (Inter-Blockchain Communication): Cosmos’ native cross-chain messaging protocol.
  • Examples of Cosmos SDK Chains: Osmosis, Secret Network, Cronos, (formerly Terra).

👉 Cosmos SDK = like WordPress for blockchains → makes it easy to launch a custom chain.

✅ In Short

  • CCIP (Chainlink): A cross-chain messaging protocol for smart contracts & assets.
  • Cosmos SDK: A toolkit to build new blockchains with cross-chain support (via IBC).

🔄 CCIP vs IBC: Cross-Chain Comparison

🔗 Chainlink CCIP (Cross-Chain Interoperability Protocol)

  • Scope: Works across many ecosystems (Ethereum, Avalanche, Polygon, etc.).
  • Focus: Cross-chain messages, tokens, and instructions for smart contracts.
  • Use cases:
    • Move tokens between chains.
    • Execute DeFi actions across L1s and L2s.
    • Connect dApps that live on different blockchains.
  • When to use: If your dApp is built on Ethereum (or another non-Cosmos chain) and you need secure multi-chain communication.

🌐 Cosmos IBC (Inter-Blockchain Communication)

  • Scope: Native to Cosmos SDK-based blockchains.
  • Focus: Trust-minimized cross-chain asset transfers & data exchange.
  • Use cases:
    • Transfer tokens between Cosmos SDK chains (e.g., ATOM → OSMO).
    • Share governance or validator data across chains.
  • When to use: If you are building a new blockchain with Cosmos SDK and want seamless cross-chain compatibility inside the Cosmos ecosystem.

⚙️ Cosmos SDK Modules

  1. Accounts / Tokens → Create native tokens and handle balances.
  2. Governance → On-chain proposals & voting for protocol changes.
  3. Staking / Validators → Proof-of-Stake consensus with validators securing the chain.
  4. IBC (Inter-Blockchain Communication) → Native protocol for connecting Cosmos chains.

🚀 Examples of Cosmos SDK Projects

  • Osmosis → A DEX (like Uniswap for Cosmos).
  • Terra (before crash) → Known for algorithmic stablecoin UST.
  • Secret Network → Focuses on privacy-preserving smart contracts.
  • Cronos → EVM-compatible chain backed by Crypto.com, bridging Cosmos ↔ Ethereum ecosystems.

✅ In Short

  • CCIP (Chainlink): Best if you’re on Ethereum or other non-Cosmos chains and need to connect across ecosystems.
  • IBC (Cosmos SDK): Best if you’re building in the Cosmos universe and want native, seamless cross-chain features.

💥 Why Terra Crashed

🔹 How UST Was Supposed to Work

Terra had two tokens:

  • UST → stablecoin, pegged to $1.
  • LUNA → governance / utility token.

Algorithmic peg mechanism:

  • 1 UST could always be swapped for $1 worth of LUNA.
  • If UST < $1 → arbitragers burn UST, mint LUNA (reduce UST supply, restore peg).
  • If UST > $1 → arbitragers burn LUNA, mint UST (increase UST supply, restore peg).

🔻 What Went Wrong

  1. Mass withdrawals
  • Billions pulled from Anchor Protocol (which offered ~20% yield).
  • Sparked heavy selling of UST.
  1. Depeg spiral
  • UST slipped below $1.
  • Holders rushed to redeem UST for LUNA.
  • Flood of new LUNA entered supply.
  1. Hyperinflation of LUNA
  • LUNA supply exploded from ~350M → trillions in days.
  • Price crashed from ~$80 → near zero.
  1. Death spiral complete
  • UST collapsed to a few cents.
  • LUNA became worthless.
  • ~$40 billion in value wiped out.

⚠️ Key Lesson

Algorithmic stablecoins (without strong collateral backing) are fragile.
When confidence breaks, the peg can enter a self-reinforcing death spiral.

🧠 What is a DAO & How Lido’s DAO + Liquid Staking Work

🔹 What is a DAO (Decentralized Autonomous Organization)

🔹 How Lido’s DAO + Liquid Staking Achieve Liquidity

Step Process
Pooling Users deposit ETH into Lido’s staking pool instead of needing 32 ETH per validator. Lido groups these deposits and delegates them to node operators. oai_citation:3‡Nansen
stTokens issued After deposit, users receive stETH (or other network equivalents) — a token that represents their stake + rewards. oai_citation:4‡Nansen
Reward accrual Over time, stETH automatically increases in value relative to ETH because staking rewards are accrued (without needing to claim manually). oai_citation:5‡Nansen
Use in DeFi Because stETH is an ERC-20, you can trade it, use as collateral, provide liquidity, etc. That means your staked ETH isn’t locked in place — you still get utility from it. oai_citation:6‡Chainlink
Governance via Lido DAO Holders of the LDO token vote on which node operators are used, fee structures, protocol upgrades, risk parameters, etc. The DAO controls many key parameters. oai_citation:7‡Nansen

🔹 Risks & Things to Watch

✅ In Sum

Lido’s model lets users stake ETH but not lose liquidity, thanks to tokenized staking (stETH), rewards accrual, and DAO governance that ensures the protocol is managed by community.

Would you like me to compare Lido vs Rocket Pool vs other liquid staking providers similarly?

🔹 What is a Blob in Ethereum (EIP-4844 / Proto-Danksharding)?

📌 Definition

  • A blob = large data packet attached to an Ethereum transaction.
  • Purpose: provide cheap, temporary storage for L2 rollups (Arbitrum, Optimism, zkSync, Base, etc.) to post compressed transaction data to Ethereum.
  • Unlike calldata, blobs are not stored forever → they are pruned after ~18 days.

🔹 Why Blobs?

Before EIP-4844:

  • Rollups used calldata to publish their transaction data.
  • This was expensive and bloated Ethereum’s permanent state.

With blobs:

  • Temporary storage → cheaper.
  • Prunable data → reduces node storage load.
  • Lower gas cost → makes rollup transactions much cheaper for users.

🔹 Example (from block #23353452)

  • Blob Tx: 1 transaction carried blob data.
  • Blob Size: 384 KiB = 3 blobs (each blob ≈ 128 KiB).
  • Blob Utilisation: 33% of block’s blob capacity used.
  • Blob Gas Price: 1 wei (0.000000001 Gwei) → very cheap.
  • Blob Gas Limit: 1,179,648 (maximum blob space per block).

✅ In Short

Blobs = temporary cheap storage for rollups.
They are the first step toward Danksharding, Ethereum’s long-term scaling solution.

🔹 Ethereum Fusaka Upgrade (Late 2025)

Fusaka is Ethereum’s upcoming network upgrade, expected in late 2025.
It focuses on scalability, efficiency, and cryptographic improvements.

✨ Key Features

  • PeerDAS (Peer Data Availability Sampling)
    Lets nodes sample data instead of storing everything → improves rollup scalability.

  • BPO (Blobs Per Object / related to EIP-4844 blobs)
    Better handling of blob transactions for L2 data availability.

  • ModExp Precompiles
    Faster cryptographic operations (important for zk-proofs and advanced math).

📊 Inclusion Stages (Chart Explained)

The chart tracks EIPs (Ethereum Improvement Proposals) considered for Fusaka:

  • 🟩 Green = Included
  • 🔵 SFI (Stage Final Inclusion) → very likely to make it in.
  • 🟠 CFI (Candidate Final Inclusion) → still being considered.
  • 🟣 DFI (Draft Final Inclusion) → early draft stage.
  • 🔴 PFI (Potential Final Inclusion) → possible, but uncertain.

Each number in the grid is an EIP ID under review.

🚀 Roadmap Context

  • Builds on Cancun/Prague (2024).
  • Paves the way for Glamsterdam upgrade (future milestone).
  • Part of Ethereum’s rollup-centric scaling roadmap.

✅ In short: Fusaka = late-2025 upgrade with PeerDAS + blob handling + zk efficiency.
It’s about making Ethereum cheaper and faster for rollups, while preparing for the next big step: Glamsterdam.

🔹 Best RPC / Node Providers (2025)

Provider Free Tier Strengths Best For
Alchemy 300M compute units/month (~30M requests) Largest free tier, super stable, great tooling (mempool watcher, NFT API, alerts) Dapp builders needing scale + stability
Infura Small free tier Battle-tested, widely used, easy integration Standard choice, simple projects
QuickNode Small free tier, paid fast Very low latency, strong analytics, NFT APIs, SOC2 security Enterprises, high-speed trading / MEV bots
Pocket Network 1M requests/day free Fully decentralized RPC, no downtime, censorship resistant Privacy / decentralization advocates
Moralis Free shared + archive nodes Web3 SDKs, NFT APIs, no logs (privacy) NFT / Web3 app developers
Allnodes PublicNode free, dedicated paid Privacy focused, pay-per-hour, supports many chains Heavy multi-chain users
Chainstack Free shared nodes GraphQL support, bring-your-own-cloud Teams needing hybrid setups
Tenderly 25M units/month free Simulations, debugging, transaction previews Smart contract devs / testers
ZMOK Paid only “Front-running as a service,” fastest block/mempool feeds MEV searchers, trading bots

✅ Recommendation (Best Deal)

  • Max free tier → Alchemy (300M calls).
  • Decentralization/privacy → Pocket Network.
  • Fastest + analytics → QuickNode.
  • Debugging/contracts → Tenderly.

Comparison: OpenZeppelin Contracts vs Foundry Tooling

Aspect OpenZeppelin Contracts / Libraries Foundry / Foundry Tooling
What it is Audited library of smart contract modules & standards (ERC-20, ERC-721, access control, proxy, utilities). Dev toolchain for Solidity/EVM: Forge (tests), Cast (CLI), Anvil (local node), plugins.
Purpose Reusable, secure building blocks; standard behaviors; reduces risk with vetted code. Facilitates coding, testing, deployment, upgrade workflows; speed, minimal overhead, Solidity tests, OZ upgrades plugin.
Upgradeable Contracts Support Includes upgradeable versions (e.g. ERC20Upgradeable) for proxy patterns. "OpenZeppelin-Foundry Upgrades" plugin: deploy, upgrade, check layout/compatibility, provides scripts.
Testing / Dev Experience Usable in any environment (Hardhat, Foundry, etc). OZ doesn't provide test runner or node. Fast tests via forge test; good fuzzing, snapshots, minimal setup, streamlined workflow.
Dependency Mgmt & Setup Installed as dependencies (npm/git). Versioning/storage layout compatibility critical for upgrades. Uses forge install/remappings. OZ integration uses reference contracts for upgrade checks.
Gas / Overhead Security/generalized; some overhead due to generic code, access control, upgrade patterns add initializers/overhead. Foundry doesn't change OZ contract gas; gives visibility into usage, storage layout, faster iteration.
Upgrade Safety / Checks Docs, versioned libs, patterns, gap variables (__gap). Foundry plugin from OZ: storage slot collision, ref contract validation, validateUpgrade for safety checks.

What is __gap?

  • __gap is a reserved storage array (e.g. uint256[50] private __gap;) in upgradeable Solidity contracts.
  • It reserves unused storage slots, so future upgrades can add new variables without shifting storage.

Why It’s Needed

  • Solidity assigns storage slots in declaration order.
  • Adding new variables in base contracts after deployment can shift storage slots in child contracts, causing storage collisions and breaking upgrades.
  • __gap reserves slots up front, letting you “use up” the reserved slots for new variables in upgrades, avoiding shifts.

How to Use & Best Practices

  • Put __gap after all declared state variables in base/abstract upgradeable contracts.
  • When adding variables later, insert before __gap and reduce its size (e.g. from [50] to [48] if you add 2 vars).
  • All contracts in the inheritance chain should maintain and update the gap size consistently.
  • Use tools like OpenZeppelin Upgrades or Foundry’s validateUpgrade to check storage layout and gap usage.

Limits & Considerations

  • __gap size should anticipate future variable additions — too large wastes declaration space, but unused slots don’t cost gas.
  • Mismanaging the gap (e.g., adding variables after the gap, or forgetting to reduce its size) can break the upgrade path.
  • Tools can help catch mistakes in storage layout and gap management.

How validateUpgrade Works

  • validateUpgrade checks that your upgraded contract is storage-compatible with the previous version.
  • It compares storage layout: ensures new variables don’t shift or overwrite existing data.
  • Detects issues like removed/renamed variables, reordering, or inserting before existing state vars.
  • Used in plugins (OpenZeppelin, Foundry) to prevent upgrade bugs before deploying.

Usage:
Run as part of your upgrade deployment scripts.
Example with OpenZeppelin plugin:

npx hardhat validate-upgrade

or

forge validate-upgrade

forge (Foundry) does not have a validate-upgrade command built-in.

How to use with Foundry:

  1. Install the OZ Upgrades plugin for Foundry.
  2. Use the scripts/commands from the plugin, not just forge alone.
  3. Check plugin docs for upgrade validation commands.

Summary:
forge validate-upgrade won’t work without the OZ plugin. Use Hardhat/Foundry with the official OpenZeppelin Upgrades tools.

Common EVM Testnets & Their Mainnets

  • Sepolia
    Chain ID: 11155111
    Mainnet: Ethereum

  • Arbitrum Sepolia
    Chain ID: 421614
    Mainnet: Arbitrum One

  • Base Sepolia
    Chain ID: 84532
    Mainnet: Base

  • Polygon Amoy
    Chain ID: 80002
    Mainnet: Polygon PoS

  • Polygon zkEVM Cardona
    Chain ID: 2442
    Mainnet: Polygon zkEVM

  • BSC Testnet
    Chain ID: 97
    Mainnet: BNB Smart Chain (BSC)

  • OP Sepolia
    Chain ID: 11155420
    Mainnet: Optimism (OP Mainnet)

  • Avalanche Fuji C-Chain
    Chain ID: 43113
    Mainnet: Avalanche C-Chain

  • Linea Sepolia
    Chain ID: 59141
    Mainnet: Linea

  • Scroll Sepolia
    Chain ID: 534351
    Mainnet: Scroll

  • ZkSync Era Sepolia
    Chain ID: 300
    Mainnet: zkSync Era

  • Monad Testnet
    Chain ID: 10143
    Mainnet: Monad

FYI:
These testnets simulate the main networks for safe, free development and testing.

Difference between ERC and EIP

  • EIP (Ethereum Improvement Proposal):

    • A formal proposal for changes or additions to Ethereum.
    • Can cover any topic: core protocol, networking, contract standards, etc.

  • ERC (Ethereum Request for Comment):

    • A type of EIP focused on application-level standards, especially smart contracts (like ERC-20, ERC-721).
    • All ERCs are EIPs, but not all EIPs are ERCs.

Summary:

  • EIP = general proposal
  • ERC = standard for applications/smart contracts (a subtype of EIP)

Are Anvil & Forge/Foundry replacements for Truffle & Ganache?

Short answer: Yes, Foundry + Anvil are widely seen as modern, faster alternatives. But there are trade‑offs.

Evidence & Features

Comparison: Foundry/Anvil vs Truffle/Ganache

Area Foundry/Anvil Truffle/Ganache
Speed / Performance Much faster compilation, testing, with Rust under the hood. oai_citation:3‡GitHub Slower, older architecture.
Testing in Solidity Yes. Forge allows writing solidity tests. oai_citation:4‡GitHub Mostly JS/TS tests.
Local Node Features Anvil supports EVM forking, RPC methods, custom mining modes. oai_citation:5‡Foundry Ganache also supports some forking, but more limited, and development now is less active.
Ecosystem & Maintenance Actively developed; Foundry has a strong developer community. oai_citation:6‡GitHub Truffle/Ganache are being sunset, less focus.

What to Consider If Migrating / Using Foundry

  • Some existing scripts/tests written for Truffle will need adjustments.
  • Plugin ecosystems differ (Hardhat, Truffle had lots of JS tooling; Foundry is more Solidity & CLI centric).
  • Learning curve for Forge & Anvil if you’re used to JS‑based tooling.
  • Some features from Ganache/Truffle that are JS integrations or UI oriented may not yet have exact equivalents in Foundry.

If you like, I can map out a migration plan from Truffle/Ganache → Foundry/Anvil for your stack.

Does Solidity Support Multiple Inheritance?

Yes — Solidity supports multiple inheritance. oai_citation:0‡GeeksforGeeks

How It Works

  • You can have a contract inherit from more than one parent contract using the is keyword. oai_citation:1‡cyfrin.io
  • Parent contracts can themselves inherit from others (multi‑level inheritance). oai_citation:2‡O'Reilly Media
  • When you inherit functions from multiple parents that define the same function signature, you must override them in the derived contract and explicitly indicate which parent(s) you’re overriding. oai_citation:3‡cyfrin.io

Rules & Details

  • Use virtual in parent contracts for functions you expect to be overridden. oai_citation:4‡cyfrin.io
  • Use override in child contracts, specifying all parents whose implementation you’re overriding. oai_citation:5‡CoinsBench
  • The order you list parent contracts matters. Solidity uses C3 linearization to resolve the order in which base contracts are evaluated. The order affects behavior of super, constructor order, etc. oai_citation:6‡cyfrin.io

Example

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract A {
    function foo() public pure virtual returns (string memory) {
        return "A";
    }
}
contract B is A {
    function foo() public pure virtual override returns (string memory) {
        return "B";
    }
}
contract C is A {
    function foo() public pure virtual override returns (string memory) {
        return "C";
    }
}

// D inherits from B, C: order matters
contract D is B, C {
    // override both parents
    function foo() public pure override(B, C) returns (string memory) {
        return super.foo();  // calls C.foo() because of inheritance order
    }
}

Why Return Type Is string memory

  • string is a reference type in Solidity (like bytes, arrays, structs). You need to specify its data location: storage, memory, or calldata. oai_citation:0‡docs.soliditylang.org
  • When a function returns a string, that string is copied out to a temporary location for the caller. memory is appropriate because:
  • storage refers to persistent state variables. Returning a storage reference would imply the caller could access or modify the contract’s persistent data through that reference, which isn't allowed or supported in many external/public call contexts. oai_citation:2‡Ethereum Stack Exchange
  • calldata is read‑only and tied to input parameters. You can’t use calldata for return values except in certain function signatures / visibility contexts; typically return values need to be in memory. oai_citation:3‡docs.soliditylang.org

Summary

  • Use string memory for returned strings because the data is temporary (not persistent), needs to be copied out to the caller, and cannot remain in storage reference safely.
  • memory gives you a correct, safe, and gas‑efficient way to return reference types from functions.

Ethereum PoS — Validator lifecycle, selection & slashing

1 • Joining

  • Stake 32 ETH to the deposit contract.
  • Run execution, consensus & validator clients.
  • Wait in the activation queue (rate-limited so the set grows smoothly).

2 • Time structure

Unit Length What happens
Slot 12 s 1 block proposer + 1 attestation committee
Epoch 32 slots ≈ 6 min Duties fixed for this window

3 • Choosing who does what

  • Randomness source: RANDAO beacon (each proposer adds entropy).
  • Block proposer: one validator per slot, weighted by effective balance (cap = 32 ETH).
  • Attesters: everyone else is shuffled into committees; each validator attests once per epoch, max.

4 • Rewards vs minor penalties

Behaviour Effect
Propose/attest on time Earn ETH
Miss duty Small penalty
Repeated downtime Bigger penalty (but not a slash)

5 • Slashing events (big penalties + forced exit)

Offence What it is
Double proposal Two blocks for the same slot
Double vote Two conflicting attestations for the same target
Surround vote New vote’s source/target wrap around an earlier vote

Slashproof logic runs client-side; anyone can submit evidence, and the whistle-blower gets a finder’s fee.

Probability note
With a full 32 ETH, chance of being proposer in any slot ≈ 1 / (# active validators). Over a year that’s ~ (slots per year) / (# validators) blocks proposed.

For exact spec pseudocode (get_beacon_proposer_index, compute_committee) feel free to ask.

Geth ≠ consensus client ≠ validator client

Layer Example software Handles Holds validator keys?
Execution Geth EVM, transactions, JSON-RPC No
Consensus Prysm, Lighthouse, Teku, Lodestar, Nimbus Beacon chain, fork-choice, duties feed Usually no*
Validator Prysm VC, Lighthouse VC, Teku VC, etc. Signs blocks & attestations Yes (BLS keys)

*Many consensus clients ship a validator-client sub-process, but you must enable it and supply your keys.

So: run Geth + one consensus client + its validator client (or an external signer) to be a full PoS validator.

Right — on mainnet Geth handles execution only, not PoS consensus.

  • Geth now just processes transactions, stores EVM state and serves JSON-RPC; consensus moved out after the Merge oai_citation:0‡go-ethereum.
  • To follow the chain you pair Geth with a beacon/consensus client (Lighthouse, Prysm, Teku, Nimbus, Lodestar) over the authenticated RPC port 8551 using a shared JWT secret oai_citation:1‡Medium.
  • The old PoW logic is still in the codebase for private nets, but stays dormant on Ethereum mainnet.

So a full node today = Geth (execution) + consensus client (+ validator keys if you stake).

Yes. Prysm bundles both components.

Role Prysm binary / image What it does
Consensus (beacon) prysm.sh beacon-chain
gcr.io/prysmaticlabs/prysm/beacon-chain		 Syncs & gossips the beacon chain
Validator prysm.sh validator
gcr.io/prysmaticlabs/prysm/validator		 Holds BLS keys, signs duties

Run them together or separately:

# consensus layer
./prysm.sh beacon-chain --mainnet --execution-endpoint=http://localhost:8551 --jwt-secret=jwt.hex

# validator(s) — can be many
./prysm.sh validator --wallet-dir=./wallet --beacon-rpc-provider=localhost:4000

Ethereum PoS Validator Cheat-Sheet

1 · Lifecycle Snapshot

Stage What happens Key command / action
Stake Send 32 ETH via Launchpad deposit contract staking-deposit-cli → upload deposit_data.json
Queue Wait until activation slot Nothing; just watch beacon explorer
Active Receive proposer / attester duties every epoch Prysm VC signs automatically
Exit Voluntary or forced (slashing) validator exit --keystore …

2 · Time Structure & Selection

  • Slot: 12 s — 1 proposer, 1 attestation committee
  • Epoch: 32 slots ≈ 6 min — duties fixed for epoch
  • Randomness: RANDAO beacon; probability ∝ effective balance (max 32 ETH)

3 · Clients Stack

Layer Typical software Holds validator keys?
Execution Geth No
Consensus Prysm (beacon-chain) No
Validator Prysm (validator) Yes

Run with a shared JWT secret on port 8551:

# execution
geth --authrpc.jwtsecret jwt.hex
# consensus
prysm.sh beacon-chain --execution-endpoint=http://127.0.0.1:8551 --jwt-secret=jwt.hex
# validator
prysm.sh validator --beacon-rpc-provider=localhost:4000

4 · Connect Your 32 ETH to Prysm Validator

1. Generate keystores offline

git clone https://github.com/ethereum/staking-deposit-cli
./deposit new-mnemonic --num_validators 1 --chain mainnet

2. Send the deposit

Go to launchpad.ethereum.org → upload deposit_data-*.json → sign & send 32 ETH.

3. Import keys into Prysm

prysm.sh validator accounts import --keys-dir /path/to/keystores

4. Start validator (see stack above).

It auto-signs once the beacon chain flags your validator active.

5. Slashing Quick Reference

Offence Penalty
Double proposal Loss + forced exit
Double / surround vote Loss + forced exit
Extended downtime Gradual balance bleed

Summary

Staking on Ethereum’s proof-of-stake chain requires a minimum deposit of 32 ETH into the official Launchpad deposit contract to activate a validator. This threshold balances network security and decentralization by ensuring each validator has significant “skin in the game.” The Launchpad interface handles key generation and builds the authenticated deposit data structure, sending it to the contract’s incremental Merkle tree. Once your 32 ETH is locked, your validator enters the activation queue—earning rewards for proposing and attesting blocks while helping secure the network.

Why 32 ETH Is the Minimum Stake

Security Against Attacks

A larger minimum stake raises the cost of mounting a 51 % attack. Requiring 32 ETH per validator means an attacker must control a substantial amount of ETH to influence consensus, making malicious behavior economically irrational.

Preventing Centralization

If the requirement were too high, only the wealthiest could participate; too low, and Sybil attacks become easier. The 32 ETH figure strikes a balance, allowing many individuals to run validators without overly fragmenting the network.

Role of the Launchpad Deposit Contract

Official Entry Point

The deposit contract is a permissionless smart contract maintained by the Ethereum Foundation. Every valid deposit emits an event and adds your validator’s public key and withdrawal credentials into its Merkle tree.

Data Integrity and Authentication

The Launchpad UI helps you generate and package your consensus-layer keys and signature into a well-formed deposit_data structure. That data is then sent in a single transaction to the contract, ensuring on-chain proof of your intent to validate.

After You Send 32 ETH

  1. Queue and Activation: Deposits enter an activation queue; once processed, your validator becomes active on the Beacon Chain.
  2. Lock-up Period: Your 32 ETH remains locked until withdrawals are enabled (post-Shanghai upgrade). During this time, it cannot be transferred or spent.
  3. Rewards & Penalties: Active validators earn rewards for correct block proposals and attestations. Downtime or equivocation leads to penalties or slashing, deducted from your staked ETH.

Alternatives for Smaller Stakes

  • Staking Pools (e.g., Lido, Rocket Pool) let you stake any amount but introduce counterparty risk and fees.
  • Centralized Exchanges offer “liquid staking” tokens representing your stake but require trust in the exchange’s custody model.

Key Takeaway: You send exactly 32 ETH via the Launchpad deposit contract because that is the protocol-defined stake required to run a solo validator. The Launchpad simplifies key management and data packaging, while the deposit contract securely records your stake and initiates your role in securing Ethereum’s network.

What Is a Sybil Attack?

A Sybil attack is a network attack in which a single adversary creates and controls many fake identities (“Sybil nodes”) to gain disproportionate influence over a system’s reputation, voting or resource-allocation mechanisms oai_citation:0‡Wikipedia.

Why It’s Called “Sybil”

The name comes from Sybil, a 1973 case-study book about a woman diagnosed with dissociative identity disorder, symbolizing multiple personalities under one person’s control oai_citation:1‡Wikipedia.

When It Emerged

  • Pre-2002 (Pseudospoofing): Early discussions of forging multiple identities on the Cypherpunks mailing list referred to this vector as “pseudospoofing” oai_citation:2‡Wikipedia.
  • 2002 (Formal Definition): John R. Douceur’s landmark paper “The Sybil Attack” at the IPTPS workshop rigorously defined the attack model and its threat to peer-to-peer systems oai_citation:3‡Wikipedia.
  • Early 2000s Onward: Microsoft researcher Brian Zill suggested the “Sybil attack” name in or before 2002; thereafter, P2P networks like BitTorrent and sensor-network protocols reported real-world Sybil exploits oai_citation:4‡Wikipedia.

RPC Endpoints Dashboard Explained

Top‐line Metrics (last 24 h)

Metric Value What it means
Total requests 4 409 547 487 All RPC calls served
Cached requests 32.81 % % of calls answered from cache (faster, cheaper)
Avg req/sec 51 036 Mean requests per second over 24 h
Current req/sec 27 962 Real-time throughput right now

Filters & Modes

  • All / Mainnet / Testnet: toggle which networks to view
  • Cosmos-only: limit to Cosmos-based chains

Ethereum Row (example)

Chain Nodes (Up / Down) 24 h Requests Endpoints
Ethereum 39 / 7 1 006 754 162 RPC • WS RPC • Beacon API
  • Nodes: number of healthy vs. offline nodes
  • Requests: total calls to Ethereum endpoints in 24 h
  • Endpoints: available connection types

Summary

You can call PublicNode’s Beacon API by sending HTTP GET/POST requests to https://ethereum-rpc.publicnode.com/eth/v1/beacon/... without any API key or special headers—just parse the JSON responses to access consensus-layer data oai_citation:0‡ethereum-rpc.publicnode.com oai_citation:1‡ethereum.github.io.

1. Base URL & Authentication

(Shown under “Beacon API” on PublicNode’s Ethereum RPC page) oai_citation:2‡ethereum-rpc.publicnode.com

2. Common Beacon Endpoints

Endpoint Method Description Source
/eth/v1/beacon/genesis GET Returns genesis_time, genesis_validators_root, genesis_fork_version QuickNode Docs oai_citation:4‡QuickNode
/eth/v1/beacon/headers GET Lists recent block headers Beacon API Spec oai_citation:5‡ethereum.github.io
/eth/v1/beacon/headers/{block_id} GET Fetches a specific block header Beacon API Spec oai_citation:6‡ethereum.github.io
/eth/v1/validator/duties/attester/{epoch} GET Attester duties for a given epoch Beacon API Spec oai_citation:7‡ethereum.github.io
/eth/v1/validator/duties/proposer/{epoch} GET Proposer duties for a given epoch Beacon API Spec oai_citation:8‡ethereum.github.io
/eth/v1/beacon/blocks POST Submit a signed full block Beacon API Spec oai_citation:9‡ethereum.github.io
/eth/v1/beacon/blinded_blocks POST Submit a blinded (MEV) block Beacon API Spec oai_citation:10‡ethereum.github.io

For the full list, see the official Beacon API specification on GitHub. oai_citation:11‡GitHub

3. Example Usage

3.1 cURL (GET genesis)

curl -X GET \
"https://ethereum-rpc.publicnode.com/eth/v1/beacon/genesis" \
-H "accept: application/json"

This returns JSON with genesis_time, genesis_validators_root, and genesis_fork_version

3.2 JavaScript (fetch)

fetch("https://ethereum-rpc.publicnode.com/eth/v1/beacon/headers", {
method: "GET",
headers: { "accept": "application/json" }
})
.then(res => res.json())
.then(data => console.log(data))
.catch(err => console.error(err));

4. Tips & Best Practices

• Rate Limits & Caching: PublicNode caches ~34% of requests to speed up responses; heavy-compute endpoints like /genesis may incur slightly higher latency . • Security & TLS: Don’t expose your Beacon API directly to the Internet. Use an Nginx proxy for caching and TLS termination before forwarding requests to your node . • Node Configuration: Beacon clients (e.g., Lighthouse) require flags like --http-enable-tls and --http-tls-cert/--http-tls-key to serve HTTPS—review your client’s docs for details . • Error Handling: Always check HTTP status codes and parse JSON error fields as defined by the Beacon API spec for troubleshooting

Why Expose Beacon APIs?

  • Consensus-Layer Data

    • Fetch validator duties, sync status, fork info, finality checkpoints.
    • Essential for monitoring/operating Eth2 clients and validators.

  • Post-Merge Architecture

    • Ethereum split into Execution (RPC) + Consensus (Beacon).
    • Beacon API isn’t outdated—it’s the live “brain” of PoS.

RPC Endpoints vs. Beacon API

Feature RPC Endpoints Beacon API
Layer Execution (transactions, state, logs) Consensus (blocks, validators, epochs)
Common Methods eth_blockNumber, eth_sendRawTx /eth/v1/beacon/headers, /validator/duties
Use-Case dApps, wallets, indexers Validator tooling, chain health checks

When to Use Which

  • RPC for everything execution-related (sending tx, reading contract state).
  • Beacon for validator orchestration and consensus metrics.

Both are active and complementary—neither is obsolete.

Category Purpose Examples
dApps User-facing apps on blockchain (UI + smart contracts) Uniswap, Aave, OpenSea
Wallets Key management & transaction signing MetaMask, Trust Wallet, Ledger
Indexers Data aggregators & query services The Graph, Covalent, Dune
Service Category Description
Uniswap dApp Decentralized exchange for swapping ERC-20 tokens via AMM pools
Aave dApp Lending/borrowing protocol offering variable & stable interest rates
OpenSea dApp NFT marketplace for minting, buying, and selling digital collectibles
MetaMask Wallet Browser/mobile wallet extension for managing keys & Web3 interactions
Trust Wallet Wallet Mobile wallet supporting multiple chains and dApp browser
Ledger Wallet Hardware wallet for offline key storage and transaction signing
The Graph Indexer Decentralized indexing protocol for querying blockchain data via GraphQL
Covalent Indexer Unified API delivering granular on-chain data across chains
Dune Indexer Analytics platform letting users build/share SQL queries & dashboards

Summary

Uniswap pools get liquidity from anyone willing to deposit matching values of the two tokens (retail users, professional market‐makers, protocols, DAOs) in exchange for LP tokens and fee income. Different LP “flavors” (passive holders vs. professional bots) tailor strategies around impermanent loss, concentrated ranges, and yield incentives. oai_citation:0‡Uniswap Labs

Who Can Be a Liquidity Provider?

Types of Liquidity Providers

Type Characteristics Source
Passive LPs Hold tokens long-term to earn trading fees; minimal active management oai_citation:4‡Uniswap Docs
Professional LPs Use custom tooling/bots for tight spreads, dynamic range adjustments oai_citation:5‡Uniswap Docs
Concentrated LPs Pick specific price ranges (v3) to maximize capital efficiency oai_citation:6‡Uniswap Docs
Protocol LPs DAOs or projects that bootstrap new pools to bootstrap liquidity oai_citation:7‡RareSkills
Institutional LPs Exchanges or funds supplying deep liquidity to reduce slippage oai_citation:8‡Amberdata Blog

Why They Provide Liquidity

Risks & Considerations

In short, Uniswap’s AMM pools are funded by a diverse set of participants—from casual token holders to professional market-makers and protocols—each motivated by fee revenue, strategic yield, or ecosystem incentives.

Summary

Lido’s stETH is a rebasing token whose balance in your wallet increases daily to reflect staking rewards (or decreases for penalties), whereas wstETH (“wrapped stETH”) is a non-rebasing ERC-20 whose balance remains constant and instead accrues value via a changing exchange rate against stETH. Wrapping stETH into wstETH enables compatibility with DeFi protocols that don’t support rebasing tokens and simplifies integrations by providing a fixed-balance asset oai_citation:0‡help.lido.fi.

1. stETH (Rebasing)

  • Mechanism: Balance adjusts algorithmically each epoch to distribute rewards/penalties directly into token balances oai_citation:1‡help.lido.fi.
  • Use-Case: Ideal for protocols (Curve, Yearn) designed to handle rebasing assets, where your on-chain stETH balance always equals your share of total pooled ETH oai_citation:2‡help.lido.fi.
  • Pros:
    • Direct reflection of staking rewards.
    • No extra wrapping/unwrapping gas.
  • Cons:
    • Many DEXes (Uniswap v2, Sushi) and lending markets aren’t compatible with tokens whose balances change externally oai_citation:3‡help.lido.fi.

2. wstETH (Non-Rebasing Wrapper)

  • Mechanism: When you wrap, your stETH is locked in the wstETH contract; wstETH’s balance stays fixed, and its exchange rate (wstETH → stETH) grows over time as rewards accrue oai_citation:4‡stake.lido.fi.
  • Use-Case: Suited for DeFi primitives requiring constant balances (Uniswap, MakerDAO, batch auctions), since wstETH holders unwrap at any time to claim the accumulated rewards in stETH oai_citation:5‡help.lido.fi.
  • Pros:
    • Simplifies integrations: protocols see a static ERC-20.
    • Avoids unexpected balance changes mid-transaction.
  • Cons:
    • Requires an explicit wrap/unwrap transaction (gas cost).
    • Slight UX overhead for end users.

3. Technical & UX Differences

Aspect stETH (Rebasing) wstETH (Wrapped)
Balance Model Dynamic; increases/decreases daily Static; balance only changes on wrap/unwrap ops
Value Accrual Direct in balance Via increasing exchange rate (wstETH → stETH)
Contract Interaction ERC-20 with rebase() calls Wrapper contract with wrap()/unwrap() methods
DeFi Compatibility Curve, Yearn (rebasing-aware) Most DEXes & lending markets (static-balance)
Gas Costs None beyond staking Additional for wrap/unwrap transactions

4. When to Choose Which

  • Hold & Farm in rebasing-aware vaults: Use stETH directly.
  • Provide liquidity on Uniswap v2/Sushi/Batch auctions or use in Collateralized Debt Positions: Use wstETH for predictable balances.
  • General DeFi integrations where token balance stability is required: wstETH is preferred oai_citation:6‡Lido Governance.

References

  1. Lido Help: “What is Lido’s wstETH?” oai_citation:7‡help.lido.fi
  2. Lido Help: “Bridging stETH/wstETH” oai_citation:8‡help.lido.fi
  3. Stake.Lido.fi FAQ oai_citation:9‡stake.lido.fi
  4. CoinMarketCap: “What Is Lido wstETH…” oai_citation:10‡CoinMarketCap
  5. CoinTelegraph: Lido & KyberSwap wstETH article oai_citation:11‡Cointelegraph
  6. Octobot: “What is Wrapped stETH” oai_citation:12‡OctoBot
  7. Glassnode Insight: stETH rewards mechanics oai_citation:13‡Glassnode Insights
  8. Reddit discussion on wrap/unwrap oai_citation:14‡Reddit

What Are Batch Auctions?

Batch auctions group together orders over a fixed time interval and execute them all at once at a single clearing price. Instead of processing trades continuously, they:

  • Collect buy and sell orders for a period (e.g. 5 minutes).
  • Aggregate total supply and demand.
  • Compute one price where supply equals demand.
  • Execute all matched orders simultaneously.

Why Use Batch Auctions?

  • Front-Running Protection: Prevents bots from jumping ahead by anticipating single trades.
  • Price Discovery: Large blocks of orders clear at a fair market price.
  • Efficiency: Reduces gas costs by settling many trades in one transaction.

Where You See Them

  • Gnosis Protocol / CowSwap – periodic on-chain auctions.
  • Token Launches – fair launch auctions for new tokens.
  • Order-matching DEXs – some DEXs offer both continuous and batch modes.

Blockchain Networks and Use Cases

General-Purpose Smart Contract Platforms

  • Ethereum
    The original smart contract blockchain.
    Use cases: DeFi, NFTs, DAOs, dApps. Most secure, but higher fees.

  • BNB Smart Chain (BSC)
    Binance-backed, low-cost, high-throughput.
    Use cases: DeFi, token launches, trading apps. Sacrifices decentralization.

  • Avalanche
    Fast, flexible with subnets for custom chains.
    Use cases: DeFi, enterprise apps, high-TPS needs.

  • Sui
    Scalable with parallel transaction execution.
    Use cases: Gaming, digital assets, consumer dApps.

  • Sonic
    Built for ultra-low latency.
    Use cases: Real-time DeFi and finance apps (emerging).

Ethereum Scaling Layers (Layer 2)

  • Polygon
    Scales Ethereum with cheap, fast transactions.
    Use cases: Gaming, NFTs, mass-market dApps.

  • Base
    Coinbase’s Layer 2, built on Optimism stack.
    Use cases: Consumer-friendly dApps, integrated with Coinbase ecosystem.

  • Optimism
    Ethereum rollup scaling solution.
    Use cases: DeFi, DAOs, NFTs with Ethereum-level security but lower costs.

DeFi-Specialized Chains

  • Osmosis
    Cosmos-based DEX chain.
    Use cases: Liquidity pools, cross-chain swaps, DeFi.

  • Injective
    Optimized for decentralized trading.
    Use cases: Order book DEXes, derivatives, synthetic assets.

Injective Overview

What it is:
Injective is a decentralized, finance-focused blockchain optimized for trading and derivatives.
It uses a high-performance Layer 1 built with the Cosmos SDK and IBC (Inter-Blockchain Communication).

Key Features

  • Order Book DEX
    Native decentralized exchange with an order book model (like traditional finance), not just AMMs.

  • Synthetic Assets
    On-chain representations of stocks, commodities, forex, and crypto indexes.
    Backed by oracles (e.g., Chainlink, Band) and stabilized by arbitrage.

  • Derivatives & Perpetuals
    Support for futures, perpetual swaps, and options across many asset classes.

  • Interoperability
    IBC-enabled, connecting Injective to the Cosmos ecosystem and beyond.

  • Low Fees & High Speed
    Built for sub-second block times and very low transaction costs.

Use Cases

  • Decentralized trading of synthetic stocks, forex, commodities.
  • Leveraged derivatives markets (perpetuals, futures).
  • DeFi applications needing fast and cheap infrastructure.
  • Cross-chain trading via Cosmos IBC.

Tagline in practice:
Injective brings Wall Street-style trading infrastructure on-chain—fast, decentralized, and globally accessible.

Injective vs Synthetix

Core Difference

  • Injective: Order book–based exchange with native trading infrastructure.
  • Synthetix: Liquidity pool model where stakers provide collateral for synthetic assets.

Architecture

  • Injective:

    • Built on Cosmos SDK with IBC (cross-chain).
    • Sub-second block times, very low fees.
    • Order book DEX with on-chain matching.

  • Synthetix:

    • Built on Ethereum (and Optimism for scaling).
    • Relies on SNX stakers to collateralize assets.
    • Uses pooled debt model instead of order books.

Synthetic Assets

  • Injective:

    • Any user can create synthetic assets.
    • Wide range: stocks, commodities, forex, crypto indices.
    • Pricing via oracles + arbitrage via order book.

  • Synthetix:

    • Predefined asset set (sUSD, sBTC, sETH, etc.).
    • Expansion depends on governance.
    • Pricing via oracles only, no order book market.

Liquidity & Trading

  • Injective:

    • Traditional order book mechanics (bids/asks).
    • Arbitrage keeps prices aligned with real-world assets.
    • Feels similar to centralized exchanges.

  • Synthetix:

    • Liquidity from global staker pool (SNX).
    • No direct counterparty—traders exchange against pooled debt.
    • Prices rely entirely on oracles.

Strengths

  • Injective:

    • Fast, cheap, highly scalable.
    • Permissionless asset creation.
    • Familiar trading UX for professionals.

  • Synthetix:

    • Deep liquidity from pooled collateral.
    • Proven Ethereum security.
    • Strong community/governance.

Weaknesses

  • Injective:

    • Ecosystem still smaller than Ethereum’s.
    • Liquidity depends on adoption of order books.

  • Synthetix:

    • High collateral requirements.
    • Slower and more expensive on Ethereum L1.
    • Oracle dependency without arbitrage mechanism.

Summary

Every on-chain transaction must be signed by an Externally Owned Account (EOA), which supplies the gas up front. When that transaction causes a smart contract to call another contract (an internal transaction), all gas costs—both for the original call and any nested calls—are drawn from the same prepaid gas supplied by the initiating EOA oai_citation:0‡Reddit.

How Gas Payment Works for Internal Calls

  1. EOA Initiation
  • Only EOAs can start transactions; contracts cannot initiate transactions on their own. Whoever signs the transaction must have enough ETH to cover its entire gas usage oai_citation:1‡Reddit.
  1. Gas Pool and Execution
  • The transaction includes a gas limit and gas price. As the EOA’s transaction executes, each operation—including any CALL, DELEGATECALL, or STATICCALL to another contract—consumes gas from that same pool oai_citation:2‡GoldRush.
  1. No Separate Payer
  • The called contract does not “pay” gas itself; it simply uses up gas from the initiating transaction’s budget. If the budget runs out, the entire transaction (including all internal calls) reverts oai_citation:3‡GoldRush.

Key Takeaway

The original EOA payer covers all gas costs—both for the primary contract invocation and for any subsequent contract-to-contract calls triggered within that transaction.

Actions Supported by an EOA (Without a Contract)

Action Description
Send ETH Create and sign a transaction to transfer ETH to any address on the network oai_citation:0‡Binance Academy
Deploy a Smart Contract Send a transaction whose data field contains contract bytecode to create a new contract account
Invoke Contract Functions Send a transaction with a data payload to call methods on an existing smart contract oai_citation:1‡Binance Academy
Transfer ERC-20 / ERC-721 Tokens Initiate token transfers by calling token contract transfer or safeTransferFrom methods oai_citation:2‡Unchained
Sign Messages Off-Chain Use eth_sign, personal_sign, or EIP-712 to sign arbitrary data or structured payloads oai_citation:3‡CoinFabrik
Approve Token Allowances Call approve on ERC-20 contracts to authorize spending by other addresses or contracts oai_citation:4‡Unchained
Batch Transactions (via Bundlers) Package multiple operations into a single signed bundle (e.g. using ERC-4337 account abstraction) oai_citation:5‡decentralizedsecurity.es

Roles on L1: Sequencer, Builder, Proposer, Validator

1. Sequencer

  • Where: Mainly on Layer 2 rollups (interacts with L1).
  • Role: Orders transactions quickly off-chain and provides instant confirmation.
  • On L1: Posts transaction batches from L2 to L1 for settlement.
  • Analogy: Traffic cop directing cars into lanes.

2. Builder

  • Where: Ethereum’s Proposer-Builder Separation (PBS).
  • Role: Constructs blocks by selecting and ordering transactions, including MEV strategies.
  • Action: Sends the fully built block to a proposer.
  • Analogy: Chef preparing a full meal.

3. Proposer

  • Where: Ethereum L1 (Proof of Stake).
  • Role: The validator selected to propose the next block.
  • In PBS: Doesn’t build the block, but chooses among blocks created by builders (usually highest bid).
  • Analogy: Waiter deciding which meal leaves the kitchen.

4. Validator

  • Where: Ethereum Proof of Stake system.
  • Role:
    • Stakes ETH to join consensus.
    • Sometimes acts as proposer (if chosen).
    • Usually acts as attester, voting on block validity.
  • Analogy: Jury that checks and finalizes the decisions.

✅ Summary

  • Sequencer (L2): Orders transactions and posts them to L1.
  • Builder (PBS): Assembles candidate blocks.
  • Proposer (PBS): Selects which block goes on-chain.
  • Validator (PoS): Secures consensus and finalizes the chain.

Solidity / Ethereum Interview Prep

🧩 Core Solidity & EVM

Q1: Difference between memory, storage, and calldata?

  • storage → persistent, written to chain (most expensive).
  • memory → temporary, erased after function call (cheaper).
  • calldata → read-only, non-modifiable, cheapest for inputs.
    Why costs differ? Because all nodes must replicate storage forever, while memory/calldata live only for execution.

Q2: What is a reentrancy attack? How to defend?

  • Attack: contract A calls contract B, which calls back into A before A updates its state, allowing repeated withdrawals.
  • Defense:
    • Checks-Effects-Interactions pattern.
    • Use ReentrancyGuard (mutex).
    • Minimize external calls.

Q3: Difference between immutable and constant?

  • constant: must be assigned at compile time. Stored directly in bytecode.
  • immutable: assigned once at deployment (constructor). Stored in storage slot but gas-optimized.
  • Use immutable if value is known only at deploy, constant if known at compile.

🔐 Security & Threat Modeling

Q4: How to prevent front-running (MEV) in contract design?

  • Use commit-reveal schemes for bids.
  • Batch transactions with fair ordering (e.g., frequent batch auctions).
  • Employ private transaction relays (e.g., Flashbots).
  • Accept some MEV but design protocol incentives to minimize harm.

Q5: How to design a safe upgradeable contract?

  • Use proxy pattern (e.g., Transparent Proxy or UUPS).
  • Store state in proxy, logic in implementation.
  • Pitfalls:
    • Storage slot collisions.
    • Breaking state layout in upgrades.
    • Require governance + timelocks for upgrade safety.

⚙️ Ethereum Protocol-Level Knowledge

Q6: How are validators selected in Ethereum PoS?

  • Time split into slots (12s) and epochs (32 slots).
  • At each slot, randomness from RANDAO + validator registry deterministically assigns:
    • One proposer.
    • Committees of attesters.
  • Consensus finalized via Casper FFG + fork choice rule LMD-GHOST.

Q7: What is a blob (EIP-4844)?

  • Temporary, cheap block data (~125 KB) introduced for rollups.
  • Lives ~2 weeks (not permanent chain storage).
  • Replaces calldata for rollup batch posting.
  • Reduces rollup fees, makes L2 scaling cheaper.
  • Works for both Optimistic and ZK rollups.

Q8: Why EL uses ECDSA, but CL uses BLS?

  • EL: ECDSA (secp256k1) → wallet ecosystem compatibility, cheap per-tx verification, inherited from Bitcoin.
  • CL: BLS → supports signature aggregation. Essential for compressing thousands of validator signatures into 1 every slot.
  • Tradeoff: ECDSA = user-friendly, BLS = consensus-scalable.

🏗️ Advanced Topics

Q9: Difference between Optimistic and ZK Rollups?

  • Optimistic → assume validity, allow fraud proofs (challenge period).
  • ZK → submit succinct proof of correctness (zk-SNARK/STARK).
  • Optimistic: simpler, but withdrawals are slow.
  • ZK: faster finality, better for complex proofs, but proving is computationally heavy.

Q10: What’s a zk-SNARK verifier contract?

  • Solidity contract that checks zk-SNARK proofs on-chain.
  • Uses elliptic curve pairings (BLS12-381).
  • Input: proof + public values.
  • Output: boolean valid/invalid.
  • Commonly generated by tools like ZoKrates or snarkjs.

📊 Practical Scenarios

Q11: Write an ETH escrow contract with reentrancy protection.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/security/ReentrancyGuard.sol";

contract Escrow is ReentrancyGuard {
    mapping(address => uint256) public deposits;

    function deposit() external payable {
        deposits[msg.sender] += msg.value;
    }

    function withdraw() external nonReentrant {
        uint256 amount = deposits[msg.sender];
        require(amount > 0, "Nothing to withdraw");
        deposits[msg.sender] = 0;
        payable(msg.sender).transfer(amount);
    }
}

Q7: What is a blob (EIP-4844)? How does it relate to calldata?

  • Before blobs → Rollups posted their batch data to Ethereum using transaction calldata.

    • Calldata is cheaper than storage but still permanent (every node stores it forever).
    • This made L2 transactions expensive and bloated on L1.

  • Blobs (EIP-4844) → Introduced in 2024 (proto-danksharding).

    • Large (~125 kB) data “blobs” can be attached to blocks.
    • Cheaper because they don’t live forever (only ~2 weeks).
    • Optimized specifically for rollup data availability.

  • Impact:

    • Rollups move from calldata → blobs.
    • Massive fee reduction.
    • L2 scaling becomes sustainable.

Summary: Calldata was the stopgap for rollups, blobs are the dedicated solution.

Q4: How to prevent front-running (MEV) in contract design?

Front-running = when an attacker (or MEV bot) sees a pending transaction in the mempool and inserts their own transaction before/around it for profit. On Ethereum this is common due to transparent mempool ordering.

Mitigation Strategies

  1. Commit–Reveal Schemes
  • Users first submit a commitment (hash of their input + secret salt).
  • Later they reveal the real input.
  • Prevents others from copying or front-running, because details are hidden until reveal.
  • Common in sealed-bid auctions, voting systems.
  1. Batch Auctions / Fair Ordering
  • Process many orders in one batch and settle them at a uniform clearing price.
  • Prevents harmful ordering because no single tx determines the outcome.
  • Example: frequent batch auctions for DEX trades.
  1. Private Transaction Relays
  • Submit transactions via systems like Flashbots, Eden, or MEV-Boost.
  • Transactions bypass the public mempool → bots can’t see them in advance.
  • Useful for high-value trades, liquidations, arbitrage.
  1. Protocol-Level Design Against MEV
  • Accept that MEV cannot be eliminated, but incentives can be aligned:
    • AMMs: Constant-product design (Uniswap v2) leaks MEV; improvements (Uniswap v3, Curve) reduce slippage.
    • MEV redistribution: Share extracted value back to users (e.g., proposer-builder separation, MEV auctions).
  • Mechanisms like enforced time delays, randomized ordering, or inclusion lists.
  1. User-Side Protections
  • Users can protect themselves by setting slippage limits, using private RPCs, or leveraging tools like Flashbots Protect.

Summary:
No silver bullet exists. Combine:

  • Cryptographic solutions (commit–reveal).
  • Market design (batch settlements, fair ordering).
  • Infrastructure (private relays, MEV-aware execution).
  • Protocol incentives (design systems to minimize harmful MEV, redistribute value).

img.png

🌐 Fundamental Differences: Ethereum vs Corda vs Solana

Ethereum

  • Type: Public, permissionless L1.
  • Consensus: Proof of Stake (Casper + LMD-GHOST).
  • Smart contracts: General-purpose (Solidity, EVM).
  • Use case: Global decentralized apps (finance, NFTs, DAOs, DeFi).
  • Trust model: Open — anyone can run a node or deploy contracts.

Corda

  • Type: Permissioned DLT (enterprise blockchain).
  • Consensus: Not a global chain — transactions are verified only by involved parties. Uses notaries (RAFT, BFT).
  • Smart contracts: JVM-based (Kotlin/Java).
  • Use case: Finance, supply chain, regulated industries.
  • Trust model: Closed consortium — known entities only.

Solana

  • Type: Public, permissionless L1.
  • Consensus: Proof of Stake + Proof of History (PoH).
  • Smart contracts: Rust-based (Sealevel runtime).
  • Use case: High-throughput dApps (DeFi, NFTs, payments).
  • Trust model: Open — but fewer validators (high hardware demands).

Summary:

  • Ethereum → decentralized, slower, secure.
  • Corda → permissioned, enterprise-focused, no global consensus.
  • Solana → fast, high throughput, decentralization trade-offs.

⚙️ Consensus Mechanisms

RAFT

  • Distributed systems consensus (not blockchain-native).
  • Leader-based → simple, fast.
  • Used in permissioned chains (Corda, Quorum).
  • Limitation: assumes honesty, not Byzantine fault tolerant.

PoW (Proof of Work)

  • Miners solve puzzles → secure, energy-intensive.
  • Sybil-resistant.
  • Used by Bitcoin, Ethereum pre-Merge.

PoS (Proof of Stake)

  • Validators stake tokens → chance to propose blocks weighted by stake.
  • Energy-efficient, slashing deters misbehavior.
  • Used by Ethereum, Solana, Cosmos.

PoA (Proof of Authority)

  • Fixed trusted validators sign blocks.
  • Very fast, centralized.
  • Used in testnets, sidechains, enterprise chains.

🧩 Byzantine Generals Problem

  • Core challenge: How can nodes agree if some are faulty/malicious?
  • PoW: Honesty from costly work.
  • PoS: Honesty from stake + slashing.
  • RAFT: Assumes no Byzantine actors, only crash faults.
  • BFT algorithms (Tendermint, HotStuff): Tolerate Byzantine actors up to 1/3.

✅ TL;DR

  • Ethereum: Public PoS smart contract chain.
  • Corda: Permissioned enterprise DLT, RAFT/BFT notaries.
  • Solana: High-speed PoS + PoH chain.
  • RAFT: Leader consensus, non-Byzantine.
  • PoW / PoS / PoA: Different economic + security trade-offs.
  • Byzantine Problem: Root issue — agreeing despite faulty/malicious nodes.

img_1.png

📦 Mempool in Ethereum PoW

1. What It Is

  • Mempool = the “waiting room” for transactions.
  • Every full node maintained a local mempool.
  • Incoming user transactions lived here before miners picked them for inclusion in a block.

2. How It Worked in PoW

  1. User signed and broadcasted a transaction.
  2. Transaction propagated across the network → nodes validated it (nonce, balance, signature).
  3. Valid transactions entered each node’s mempool.
  4. Miners selected transactions from their mempool to build candidate blocks.
  • Priority = highest gas price first.
  • Miners could reorder, include, or exclude transactions (basis for MEV).
  1. When a miner solved the PoW puzzle → block was broadcast.
  2. All included transactions were removed from mempools across the network.

3. Key Notes

  • There was no single global mempool → each node had its own.
  • Pending transactions weren’t guaranteed to be seen by everyone.
  • This design enabled front-running and MEV (bots watching mempools).

✅ Summary

Yes, Ethereum PoW had a mempool.

  • Nodes stored valid but unconfirmed transactions.
  • Miners picked from it (usually by gas price) when proposing blocks.
  • It was the battlefield for gas wars, arbitrage, and MEV.

📦 Mempool in Ethereum PoW

1. What It Is

  • Mempool = the “waiting room” for transactions.
  • Every full node maintained a local mempool.
  • Incoming user transactions lived here before miners picked them for inclusion in a block.

2. How It Worked in PoW

  1. User signed and broadcasted a transaction.
  2. Transaction propagated across the network → nodes validated it (nonce, balance, signature).
  3. Valid transactions entered each node’s mempool.
  4. Miners selected transactions from their mempool to build candidate blocks.
  • Priority = highest gas price first.
  • Miners could reorder, include, or exclude transactions (basis for MEV).
  1. When a miner solved the PoW puzzle → block was broadcast.
  2. All included transactions were removed from mempools across the network.

3. Key Notes

  • There was no single global mempool → each node had its own.
  • Pending transactions weren’t guaranteed to be seen by everyone.
  • This design enabled front-running and MEV (bots watching mempools).

✅ Summary

Yes, Ethereum PoW had a mempool.

  • Nodes stored valid but unconfirmed transactions.
  • Miners picked from it (usually by gas price) when proposing blocks.
  • It was the battlefield for gas wars, arbitrage, and MEV.

🏦 SDX Digital Bond Issuance on Corda

1. Why Corda?

  • Permissioned DLT → fits regulated finance (banks, exchanges).
  • Privacy → only transaction participants see the data.
  • Identity → all participants are KYC’d, legally recognized entities.
  • Finality → legal certainty of transactions (critical for securities).

2. Fungible Token Model

  • Corda doesn’t use ERC-20; instead, it uses state objects + contracts.
  • Bonds modeled as fungible token states using Corda’s Token SDK.
  • Each bond unit = a state object (fungible, transferable).
  • Supports fractional issuance (e.g., CHF 1,000 units).

3. Architecture

  • Issuer Node (SDX / Bank): Creates and issues the digital bond.
  • Investor Nodes: Hold and transfer bond token states.
  • Notary Service: Provides consensus (RAFT or BFT) and prevents double-spending.
  • Regulatory/Observer Nodes: Get copies of transactions for compliance.

Flow:

  1. Issuer defines bond terms (face value, coupon, maturity).
  2. Smart contract logic enforces issuance and transfer validity.
  3. Investors receive fungible token states representing bond units.
  4. Coupon payments and redemptions can be automated with workflows.

4. Benefits

  • Token SDK → easy issuance and transfer of fungible bonds.
  • Privacy → transactions shared only with involved parties.
  • Integration → connects with existing custody/settlement systems.
  • Legal certainty → aligned with Swiss DLT laws for securities.

✅ Summary

SDX digital bonds = fungible tokenized bond states on Corda.

  • Issued by banks/exchanges, held by investors, validated by notaries.
  • Each unit of a bond is a fungible state governed by smart contract rules.
  • Corda enables privacy, compliance, and legal finality, making it suitable for regulated digital securities.

About

No description, website, or topics provided.

Resources

Readme
Activity

Stars

0 stars

Watchers

0 watching

Forks

0 forks
Report repository

Releases

No releases published

Packages

No packages published

Languages