Introducing ZIP-48 Support, Secure Message Signing, and Public Key Retrieval

[jeffrystone]

The snap now brings full ZIP-48 transparent multisig support with Asigna into MetaMask Snaps by exposing new RPC methods that can be invoked via wallet_invokeSnap. Every method enforces well-formed ZIP-48 derivation paths (starting with m/…), derives keys through snap_getBip32Entropy, and displays a user-facing confirmation dialog before any sensitive action is performed.

• signTransparent – takes a list of transaction sighashes tied to a ZIP-48 derivation path, shows the recipient/amount/network to the user, and upon confirmation returns DER signatures with SIGHASH_ALL, ready to be assembled into the multisig transaction.
• signTransparentMessage – signs arbitrary text messages with the selected transparent key, applies ZIP-302 message framing, verifies the signature on-device, and optionally checks the derived address against a provided expectedAddress to prevent account mix-ups.
• getTransparentPublicKey – safely derives and returns the compressed public key for any ZIP-48 path after the user approves a dialog showing the origin and requested derivation path.

This makes the snap cover the full transparent ZIP-48 workflow—transaction signing, message signing, and key disclosure—with explicit user consent at each step.