public ServerCommitment[][] SignHashes(SignaturesRequest sigRequest)
{
// Almost done, just need to confirm a typo and a function.
// Step 5
if (sigRequest == null)
{
throw new ArgumentNullException(nameof(sigRequest));
}
var hashesCount = sigRequest.Hashes.Select(a => a.Length).Sum();
if (hashesCount != Parameters.GetTotalTransactionsCount())
{
throw new ArgumentException($"Incorrect number of hashes, expected {Parameters.GetTotalTransactionsCount()}");
}
AssertState(PromiseServerStates.WaitingHashes);
// 2D array of pairs of puzzles and promises (z_i, c_i).
var promises = new ServerCommitment[Parameters.PaymentsCount][];
// 2D array of encrypted signatures with their solutions.
var encryptedSignatures = new EncryptedSignature[Parameters.PaymentsCount][];
// 1-D array is used to store the epsilons for each column to be used when Hashing.
var previousSolutions = new byte[Parameters.GetTotalTransactionsCountPerLevel()][];
previousSolutions = previousSolutions.Select(a => new byte[0]).ToArray(); // Initialize to empty array of bytes
for (int i = 0; i < Parameters.PaymentsCount; i++)
{
promises[i] = new ServerCommitment[sigRequest.Hashes[i].Length]; // Initialization
encryptedSignatures[i] = new EncryptedSignature[promises[i].Length]; // Initialization
for (int j = 0; j < promises[i].Length; j++)
{
var hash = sigRequest.Hashes[i][j];
// Sign the hash value
var ecdsa = InternalState.EscrowKey.Sign(hash);
// Convert Signature to Bytes.
var ecdsaDER = ecdsa.ToDER();
// This can be replaced by "Utils.GenerateEncryptableInteger(Key)" if padding when XORing is not important.
var key = (new XORKey(Parameters.ServerKey)).ToBytes(); // This just generates a random epsilon.
// Append the new epsilon to the list of epsilons we have for that column to create "epsilon_{i-1,j}|| . . . , epsilon_{0,j}".
previousSolutions[j] = Utils.Combine(key, previousSolutions[j]);
// Create the padded solution with the following format "i||j||epsilon_{i,j}||epsilon_{i-1,j}|| . . . , epsilon_{0,j}"
var paddedSolutions = new PuzzleSolution(Utils.Combine(NBitcoin.Utils.ToBytes((uint)i, true), NBitcoin.Utils.ToBytes((uint)j, true), previousSolutions[j]));
// Hash and XOR the padded solution with the signature we have.
var promise = XORKey.XOR(paddedSolutions._Value.ToByteArrayUnsigned(), ecdsaDER); // This function needs to be approved "XOR".
PuzzleSolution solution = new PuzzleSolution(key); // Epsilon
// Encrypt the epsilon value using RSA
var puzzle = Parameters.ServerKey.GeneratePuzzle(ref solution);
promises[i][j] = new ServerCommitment(puzzle.PuzzleValue, promise);
encryptedSignatures[i][j] = new EncryptedSignature(ecdsa, hash, solution);
}
}
InternalState.Status = PromiseServerStates.WaitingRevelation;
InternalState.EncryptedSignatures = encryptedSignatures;
InternalState.FakeIndexesHash = sigRequest.FakeIndexesHash;
return(promises);
}
public State GetInternalState()
{
State state = Serializer.Clone(InternalState);
state.Salts = null;
state.FeeVariations = null;
state.Commitments = null;
if (_Hashes != null)
{
var commitments = new ServerCommitment[_Hashes.Length][];
var salts = new uint256[_Hashes.Length][];
var feeVariations = new Money[_Hashes.Length][];
for (int i = 0; i < _Hashes.Length; i++)
{
salts[i] = new uint256[_Parameters.FakeTransactionCountPerLevel];
feeVariations[i] = new Money[_Parameters.RealTransactionCountPerLevel];
commitments[i] = new ServerCommitment[_Hashes[i].Length];
int fakeJ = 0, realJ = 0;
for (int j = 0; j < _Hashes[i].Length; j++)
{
if (_Hashes[i][j] is FakeHash fake)
{
salts[i][fakeJ++] = fake.Salt;
}
if (_Hashes[i][j] is RealHash real)
{
feeVariations[i][realJ++] = real.FeeVariation;
}
commitments[i][j] = _Hashes[i][j].Commitment;
}
}
state.Salts = salts;
state.FeeVariations = feeVariations;
state.Commitments = commitments;
}
return(state);
}
