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spruceid / did-tezos

The Decentralized Identifier method for the Tezos blockchain.
https://did-tezos.spruceid.com
Apache License 2.0
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Deriving public key #3

Closed clehner closed 3 years ago

clehner commented 3 years ago

Examples of Derived did:tz DID documents include a publicKeyBase58 value. How is this derived? Since Tezos addresses are based on a hash of the public key, doesn't this mean a resolver cannot derive a Tezos DID's public key from the DID alone? A verifier needs the public key to verify a proof signed by a did:tz. Public keys could be retrieved from the blockchain/network, but I understand that did:tz addresses are supposed to able to work offine, also before any rotations. To enable verification for the offline use case, I think a VC/VP issuer will need to include their public key in the proof and/or credential/presentation. Typically a proof references its public key for verification using the verificationMethod property with a URL or DID URL. Possibly we could add a query string or path to the DID, and use that for the verificationMethod. Then the resolver could use the query string or path to reconstruct the public key in the DID document.

wyc commented 3 years ago

Yes, I believe the verification method/credential must contain the public key for tz1, but for tz2 and tz3 you can use ecrecover because it is supported by ECDSA.

clehner commented 3 years ago

This was implemented, for tz1, in https://github.com/spruceid/ssi/pull/76 and https://github.com/spruceid/ssi/pull/92.

I put the publicKeyJwk in the proof object. publicKeyBase58 would be more compact so maybe could use that in the future (did-core allows either key representation).

These proof type and verification method type should probably be specified in their own document or in this one:

For comparison these are the specs for the other proof/key types that DIDKit supports: