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bitcoin-keychain

Keychain gRPC service for Bitcoin (like) currencies

Intro

bitcoin-keychain is a RPC server that helps you derive new addresses from an xpub and maintains mapping between those.

The responsibilities of keychain are:

  • derive address for a given derivation path
  • get fresh receive and change addresses
  • reverse lookup of address to derivation path: for transaction creation, we need to check the address associated to the path belong to the account (not asked by protocol but by hardware wallet)
  • get the public key of an address: needed for transaction creation by protocol
  • manage gaps

The interface is defined as protobuf

Architecture

archi

Data can be stored in different backend:

  • redis
  • in memory
  • WD

We use "in memory" storage for tests / development.

In production, both "redis" and "wd" write in a redis database. The difference is "wd" write in the wallet daemon's "user pref" format for smooth transition with the wallet daemon.

You have to choose which backend with the environment variable STORE_TYPE

All data stored can be recalculated from xpubs at the price of a costly computation, so you can see this component as a cache.

Tests

We have unittest and integration test

Unittest

mage test

Integration test

mage integration

This test suite create a grpc client and a keychain server running in "redis" mode. This mean you also need to setup a redis server to run those tests.

Related component

The keychain is used by lama

The keychain use lib-grpc for Hierarchical Deterministic Wallets computation (lib-grpc uses btcsuite itself)

Workflow

The keychain is part of the LAMA suite. It provides services related to btc addresses management.

When a new account is registered, the keychain has to be called on CreateKeychain with the xpub and some other information This methods returns a keychain id (among other informations). It is a UUID randomly created. This UUID will be needed for all subsequent communication, so all keychain client needs to store it.

When this is done, the LAMA btc worker needs to regularly maintains the address usage status with MarkAddressesAsUsed This method needs a list of addresses and the keychain id. This is typically done after scanning the explorer or after a new transaction

When new addresses are needed, either for receiving fund or for UTXO, the keychain client can call one of GetFreshAddresses or GetAllObservableAddresses