Cobo Vault integration sample

This repo shows how Cobo Vault can be integrated with a watch-only wallet application.

Currently, we have two ways to export info of Cobo Vault.

QRCode and microSD-card.

QRCode is used both in All-Coins version and BTC-Only version.

microSD-card is only used in BTC-Only version.

QRCode

The data to be transferred is large, so we split the data into small fragments can be displayed in single QRCodes and combine them by an animated QRCode protocol.

All-Coins

This version of QRCode uses a json wrapper to combine the data fragments.

The whole data will be split by:

split(base64.encode(dataBuffer), capacity)

or

split(base64.encode(gzip.zip(dataBuffer)), capacity)

One QRCode contains following fields:

{
  "total": 5,
  "index": 0,
  "checkSum": "",
  "value": "",
  "compress": true,
  "valueType": "protobuf" 
}

total: identify the length of all fragments

index: identify current fragment index, starts from 0

checksum: a md5 string for whole data

value: current fragment value, it is one part of whole data

compress: whether the process has compressing step;

valueType: would only be 'protobuf'

When you collect all the QRCodes, you can extract the value and order them by index then concat them into one string, then decode it:

base64.decode(orderedFragments.join(''))

or

gzip.unzip(base64.decode(orderedFragments.join('')))

then you will get a protobuf data which described at crypto-coin-message just decode it with any protobuf library.

BTC-only

In this version we follow the BCR-UR format to organize animated QRCodes.

We provide a simple implementation here: BC-UR;

You can just collect the animated QRCodes and send the string array to BC-UR's decode method. More details in BC-UR;

microSD card

A wallet json file can be exported into microSD card looks like:

{
  "ExtPubKey": "",
  "MasterFingerprint": "",
  "CoboVaultFirmwareVersion": "",
  "DerivationPath": ""
}

ExtPubKey: the extended public key of DeribationPath

MasterFingerprint: the master key's fingerprint, big endian

CoboVaultFirmwareVersion: version number in string

DerivationPath: the bip32 derivation path of ExtPubKey

All the transactions base on PSBT.

You can write an unsigned PSBT binary file named xxx.psbt into microSD card and insert it into Cobo Vault.

Then you can find the file in Cobo Vault and sign it. After that, a signed-xxx.psbt would be found in sd card, you can broadcast it in watch-only wallet.