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hyperledger / anoncreds-spec

The specification for AnonCreds verifiable credential exchange.
https://hyperledger.github.io/anoncreds-spec/
Apache License 2.0
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WIP refactor issuance protocol text #183

Closed wip-abramson closed 12 months ago

wip-abramson commented 1 year ago

This is a start to address the issue I raised in #181.

Not made it all the way through the spec yet - at about Section 7. I seem to be making a fair few changes here, so comments and feedback welcome as I go.

Also, I recommend we update the following diagrams:

wip-abramson commented 1 year ago

Getting there...

I am not fully certain how the blinding factor is generated in RSA, so we should check this.

wip-abramson commented 1 year ago

Okay, I think the last piece is around 8.4 Receiving a Credential.

I need to look into the protocol, but I am pretty certain there should be a step here that transforms the credential signature from the issuer (A,e,v) into (A',e',v') using the blinding factor. Where the credential signature stored by the holder is (A',e',v').

wip-abramson commented 12 months ago

So I checked the CL signature code.

This is the line where the prover does the operation to remove the blinding from the credential signature L635. Called from L237 in process_credential_signature.

This line is

p_cred.v = v_prime.add(&p_cred.v)?;

Which mutates the V value of the credential signature. Note that v_prime, is the credential blinding factor.

wip-abramson commented 12 months ago

Cool! Apologies I counldn't make the call

swcurran commented 12 months ago

Thanks for the PR and issues, @wip-abramson. Working on the spec today — continuing the cleanup.