public static bool Verify(Transcript transcript, IEnumerable <Statement> statements, IEnumerable <Proof> proofs)
{
Guard.Same(nameof(proofs), proofs.Count(), statements.Count());
// Before anything else all components in a compound proof commit to the
// individual sub-statement that will be proven, ensuring that the
// challenges and therefore the responses depend on the statement as a
// whole.
foreach (var statement in statements)
{
transcript.CommitStatement(statement);
}
// After all the statements have been committed, the public nonces are
// added to the transcript. This is done separately from the statement
// commitments because the prover derives these based on the compound
// statements, and the verifier must add data to the transcript in the
// same order as the prover.
foreach (var proof in proofs)
{
transcript.CommitPublicNonces(proof.PublicNonces);
}
// After all the public nonces have been committed, a challenge can be
// generated based on transcript state. Since challenges are deterministic
// outputs of a hash function which depends on the prover commitments, the
// verifier obtains the same challenge and then accepts if the responses
// satisfy the verification equation.
var challenge = transcript.GenerateChallenge();
return(Enumerable.Zip(statements, proofs, (s, p) => s.CheckVerificationEquation(p.PublicNonces, challenge, p.Responses)).All(x => x));
}
public ProverCommitToNonces CommitToStatements(Transcript transcript)
{
// Before anything else all components in a compound proof commit to the
// individual sub-statement that will be proven, ensuring that the
// challenges and therefore the responses depend on the statement as a
// whole.
transcript.CommitStatement(Knowledge.Statement);
return((WasabiRandom random) => CommitToNonces(transcript, random));
}
public static IEnumerable <Proof> Prove(Transcript transcript, IEnumerable <Knowledge> knowledge, WasabiRandom random)
{
// Before anything else all components in a compound proof commit to the
// individual sub-statement that will be proven, ensuring that the
// challenges and therefore the responses depend on the statement as a
// whole.
foreach (var k in knowledge)
{
transcript.CommitStatement(k.Statement);
}
var deferredResponds = new List <DeferredProofCreator>();
foreach (var k in knowledge)
{
// With all the statements committed, generate a vector of random secret
// nonces for every equation in underlying proof system. In order to
// ensure that nonces are never reused (e.g. due to an insecure RNG) with
// different challenges which would leak the witness, these are generated
// as synthetic nonces that also depend on the witness data.
var secretNonceProvider = transcript.CreateSyntheticSecretNonceProvider(k.Witness, random);
ScalarVector secretNonces = secretNonceProvider.GetScalarVector();
// The prover then commits to these, adding the corresponding public
// points to the transcript.
var equations = k.Statement.Equations;
var publicNonces = new GroupElementVector(equations.Select(equation => secretNonces * equation.Generators));
transcript.CommitPublicNonces(publicNonces);
deferredResponds.Add((challenge) => new Proof(publicNonces, k.RespondToChallenge(challenge, secretNonces)));
}
// With the public nonces committed to the transcript the prover can then
// derive a challenge that depend on the transcript state without needing
// to interact with the verifier, but ensuring that they can't know the
// challenge before the prover commitments are generated.
Scalar challenge = transcript.GenerateChallenge();
return(deferredResponds.Select(createProof => createProof(challenge)));
}
