public bool CheckSign(byte[] file, byte[] signature, PrivateKey key)
{
var decryptedHash = rsa.Decrypt(signature, key);
var calculatedHash = hasher.CalcHash(file);
return Enumerable.SequenceEqual(decryptedHash, calculatedHash);
}
public byte[] Decrypt(byte[] message, PrivateKey key)
{
var keySize = key.r.ToByteArray().Length;
var encryptedBlockSize = keySize;
var sourceBlockSize = keySize - 2;
var numberBlocks = message.Length / encryptedBlockSize;
if (message.Length % encryptedBlockSize != 0)
throw new ArgumentException("Wrong size of encrypted message");
var decryptedMessage = new byte[numberBlocks * sourceBlockSize];
Parallel.For(0, numberBlocks - 1, (i) =>
//for (var i = 0; i < numberBlocks; i++)
{
var part = new byte[encryptedBlockSize];
Array.Copy(message, i * encryptedBlockSize, part, 0, encryptedBlockSize);
var Mi = new BigInteger(part);
var mi = BigInteger.ModPow(Mi, key.d, key.r);
Array.Copy(mi.ToByteArray(), 0, decryptedMessage, i * sourceBlockSize, sourceBlockSize);
});
var lastPart = new byte[encryptedBlockSize];
Array.Copy(message, (numberBlocks - 1) * encryptedBlockSize, lastPart, 0, encryptedBlockSize);
var lMi = new BigInteger(lastPart);
var lmi = BigInteger.ModPow(lMi, key.d, key.r);
var lmiBytes = lmi.ToByteArray();
var countBytes = lmiBytes.Length;
Array.Copy(lmi.ToByteArray(), 0, decryptedMessage, (numberBlocks - 1) * sourceBlockSize, countBytes);
var realSize = sourceBlockSize * (numberBlocks - 1) + countBytes;
var trimMessage = new byte[realSize];
Array.Copy(decryptedMessage, 0, trimMessage, 0, realSize);
return trimMessage;
}
