FIP: Auth Addresses · farcasterxyz protocol · Discussion #225

Authors @v, @horsefacts and @sanjay propose "auth addresses," a new Key Registry key type that lets an Ethereum address sign in on behalf of a Farcaster user without sharing custody credentials. A custody address adds an auth address to the registry, after which apps performing Sign in With Farcaster should accept its signatures for that fid. The article's example has Coinbase Wallet generate an ECDSA auth address and an Ed25519 signer, then add both in a single transaction. Auth keys cannot add signers onchain for now, and revoking an auth address is permanent. Transferring an fid does not revoke its auth addresses.