CoinSpend::CoinSpend(const Params* p, const PrivateCoin& coin,
Accumulator& a, const AccumulatorWitness& witness, const SpendMetaData& m):
denomination(coin.getPublicCoin().getDenomination()),
coinSerialNumber((coin.getSerialNumber())),
accumulatorPoK(&p->accumulatorParams),
serialNumberSoK(p),
commitmentPoK(&p->serialNumberSoKCommitmentGroup, &p->accumulatorParams.accumulatorPoKCommitmentGroup),
metadata(m) {
// 1: Generate two separate commitments to the public coin (C), each under
// a different set of public parameters. We do this because the RSA accumulator
// has specific requirements for the commitment parameters that are not
// compatible with the group we use for the serial number proof.
// Specifically, are serial number proof requires the order of the commitment group
// to be the same as the modulus of the upper group.
const Commitment fullCommitmentToCoinUnderSerialParams(&p->serialNumberSoKCommitmentGroup, coin.getPublicCoin().getValue());
this->serialCommitmentToCoinValue = fullCommitmentToCoinUnderSerialParams.getCommitmentValue();
const Commitment fullCommitmentToCoinUnderAccParams(&p->accumulatorParams.accumulatorPoKCommitmentGroup, coin.getPublicCoin().getValue());
this->accCommitmentToCoinValue = fullCommitmentToCoinUnderAccParams.getCommitmentValue();
// 2. Generate a ZK proof that the two commitments contain the same public coin.
this->commitmentPoK = CommitmentProofOfKnowledge(&p->serialNumberSoKCommitmentGroup, &p->accumulatorParams.accumulatorPoKCommitmentGroup, fullCommitmentToCoinUnderSerialParams, fullCommitmentToCoinUnderAccParams);
// Now generate the two core ZK proofs:
// 3. Proves that the committed public coin is in the Accumulator (PoK of "witness")
this->accumulatorPoK = AccumulatorProofOfKnowledge(&p->accumulatorParams, fullCommitmentToCoinUnderAccParams, witness, a);
// 4. Proves that the coin is correct w.r.t. serial number and hidden coin secret
// (This proof is bound to the coin 'metadata', i.e., transaction hash)
this->serialNumberSoK = SerialNumberSignatureOfKnowledge(p, coin, fullCommitmentToCoinUnderSerialParams, signatureHash());
}
CoinSpend::CoinSpend(const Params* p, const PrivateCoin& coin,
Accumulator& a, const AccumulatorWitness& witness, const SpendMetaData& m):
params(p),
denomination(coin.getPublicCoin().getDenomination()),
coinSerialNumber((coin.getSerialNumber())),
accumulatorPoK(&p->accumulatorParams),
serialNumberSoK(p),
commitmentPoK(&p->serialNumberSoKCommitmentGroup, &p->accumulatorParams.accumulatorPoKCommitmentGroup) {
// Sanity check: let's verify that the Witness is valid with respect to
// the coin and Accumulator provided.
if (!(witness.VerifyWitness(a, coin.getPublicCoin()))) {
throw ZerocoinException("Accumulator witness does not verify");
}
// 1: Generate two separate commitments to the public coin (C), each under
// a different set of public parameters. We do this because the RSA accumulator
// has specific requirements for the commitment parameters that are not
// compatible with the group we use for the serial number proof.
// Specifically, our serial number proof requires the order of the commitment group
// to be the same as the modulus of the upper group. The Accumulator proof requires a
// group with a significantly larger order.
const Commitment fullCommitmentToCoinUnderSerialParams(&p->serialNumberSoKCommitmentGroup, coin.getPublicCoin().getValue());
this->serialCommitmentToCoinValue = fullCommitmentToCoinUnderSerialParams.getCommitmentValue();
const Commitment fullCommitmentToCoinUnderAccParams(&p->accumulatorParams.accumulatorPoKCommitmentGroup, coin.getPublicCoin().getValue());
this->accCommitmentToCoinValue = fullCommitmentToCoinUnderAccParams.getCommitmentValue();
// 2. Generate a ZK proof that the two commitments contain the same public coin.
this->commitmentPoK = CommitmentProofOfKnowledge(&p->serialNumberSoKCommitmentGroup, &p->accumulatorParams.accumulatorPoKCommitmentGroup, fullCommitmentToCoinUnderSerialParams, fullCommitmentToCoinUnderAccParams);
cout << "GNOSIS DEBUG: commitmentPoK is " << this->commitmentPoK.GetSerializeSize(SER_NETWORK, PROTOCOL_VERSION) << " bytes" << endl;;
// Now generate the two core ZK proofs:
// 3. Proves that the committed public coin is in the Accumulator (PoK of "witness")
this->accumulatorPoK = AccumulatorProofOfKnowledge(&p->accumulatorParams, fullCommitmentToCoinUnderAccParams, witness, a);
cout << "GNOSIS DEBUG: accPoK is " << this->accumulatorPoK.GetSerializeSize(SER_NETWORK, PROTOCOL_VERSION) << " bytes" << endl;;
// 4. Proves that the coin is correct w.r.t. serial number and hidden coin secret
// (This proof is bound to the coin 'metadata', i.e., transaction hash)
this->serialNumberSoK = SerialNumberSignatureOfKnowledge(p, coin, fullCommitmentToCoinUnderSerialParams, signatureHash(m));
cout << "GNOSIS DEBUG: snSoK is " << this->serialNumberSoK.GetSerializeSize(SER_NETWORK, PROTOCOL_VERSION) << " bytes" << endl;;
}
