private byte[] XorKeySizePadding(BigInteger cipheredAgainPreviousBlock, BigInteger block)
{
byte[] xorResult = BigIntegerExtensions.UnsignedToBytes(cipheredAgainPreviousBlock ^ block);
int keySize = rsa.ExportParameters().Modulus.Length;
return(BlockCipherSupport.PadWithZeros(xorResult, keySize));
}
private void DecipherBlocks(List <byte[]> blocks)
{
for (int i = 0; i < blocks.Count; i++)
{
BigInteger nonceCounterXor = InitializationVector ^ new BigInteger(i);
byte[] nonceCounterXorBytes = rsa.Encrypt(BigIntegerExtensions.UnsignedToBytes(nonceCounterXor));
nonceCounterXor = BigIntegerExtensions.UnsignedFromBytes(nonceCounterXorBytes);
BigInteger block = BigIntegerExtensions.UnsignedFromBytes(blocks[i]);
block ^= nonceCounterXor;
blocks[i] = BlockCipherSupport.PadWithZeros(BigIntegerExtensions.UnsignedToBytes(block), BlockSize);
}
}
private void CipherBlocks(List <byte[]> blocks)
{
for (int i = 0; i < blocks.Count; i++)
{
BigInteger nonceCounterXor = InitializationVector ^ new BigInteger(i);
byte[] nonceCounterXorBytes = rsa.Encrypt(BigIntegerExtensions.UnsignedToBytes(nonceCounterXor));
nonceCounterXor = BigIntegerExtensions.UnsignedFromBytes(nonceCounterXorBytes);
BigInteger block = BigIntegerExtensions.UnsignedFromBytes(blocks[i]);
block ^= nonceCounterXor;
RSAParameters parameters = rsa.ExportParameters();
int keySize = parameters.Modulus.Length;
blocks[i] = BlockCipherSupport.PadWithZeros(BigIntegerExtensions.UnsignedToBytes(block), keySize);
}
}
public byte[] Decipher(byte[] data)
{
RSAParameters parameters = rsa.ExportParameters();
int keySize = parameters.Modulus.Length;
List <byte[]> blocks = BlockCipherSupport.DivideIntoBlocks(data, keySize);
for (int i = 0; i < blocks.Count; i++)
{
blocks[i] = rsa.Decrypt(blocks[i]);
blocks[i] = BlockCipherSupport.PadWithZeros(blocks[i], BlockSize);
}
return(BlockCipherSupport.RemovePadding(BlockCipherSupport.ConcatenateBlocks(blocks)));
}
private List <byte[]> DecipherBlocks(List <byte[]> blocks)
{
List <byte[]> decipheredBlocks = new List <byte[]>(blocks.Count);
for (int i = 0; i < blocks.Count; i++)
{
byte[] cipheredPreviousBlock = GetCipheredPreviousBlock(blocks, i);
BigInteger cipheredAgainPreviousBlock = BigIntegerExtensions.UnsignedFromBytes(rsa.Encrypt(cipheredPreviousBlock)); // Cipher intended
BigInteger block = BigIntegerExtensions.UnsignedFromBytes(blocks[i]);
decipheredBlocks.Add(BigIntegerExtensions.UnsignedToBytes(cipheredAgainPreviousBlock ^ block));
decipheredBlocks[i] = BlockCipherSupport.PadWithZeros(decipheredBlocks[i], BlockSize);
}
return(decipheredBlocks);
}
private List <byte[]> DecipherBlocks(List <byte[]> blocks)
{
List <byte[]> decipheredBlocks = new List <byte[]>(blocks.Count);
for (int i = 0; i < blocks.Count; i++)
{
var previousXor = CalculatePreviousXor(blocks, i, decipheredBlocks);
decipheredBlocks.Add(rsa.Decrypt(blocks[i]));
var decipheredBlock = BigIntegerExtensions.UnsignedFromBytes(decipheredBlocks[i]);
decipheredBlock ^= previousXor;
decipheredBlocks[i] = BigIntegerExtensions.UnsignedToBytes(decipheredBlock).Take(BlockSize).ToArray();
decipheredBlocks[i] = BlockCipherSupport.PadWithZeros(decipheredBlocks[i], BlockSize);
}
return(decipheredBlocks);
}
private byte[] XorWithBlockSizePadding(BigInteger beforeXorBlock, BigInteger block)
{
byte[] xorResult = BigIntegerExtensions.UnsignedToBytes(beforeXorBlock ^ block);
return(BlockCipherSupport.PadWithZeros(xorResult, BlockSize));
}