public byte [] Decrypt(byte [] cipher)
{
//int iters = cipher.Length / 8;
int blockSize = _tdcsp.IV.Length;
int rem = cipher.Length % 16;
if (rem != 0)
{
throw new Exception("must be in 16 byte blocks");
}
byte [] lastBlock = new byte[blockSize];
Array.Copy(cipher, cipher.Length - blockSize, lastBlock, 0, blockSize);
//reuse passed in Rijndael
byte [] origKey = (byte[])_tdcsp.Key.Clone();
byte [] origIv = (byte[])_tdcsp.IV.Clone();
//_tdcsp.Key = (byte[]) _tdcsp.Key.Clone();
_tdcsp.IV = lastBlock;
//tempTdcsp.Mode = CipherMode.ECB;
//TODO make this support other lengths 0x01 - 0x07070707070707
//byte [] pkcs5 = new byte [] {0x08,0x08,0x08,0x08,0x08,0x08,0x08,0x08};
byte [] pkcs5 = new byte [] { 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x10 };
byte [] padPlus = _tdcsp.EncryptValue(pkcs5);
byte [] paddedCipher = new byte [cipher.Length + blockSize];
Array.Copy(cipher, 0, paddedCipher, 0, cipher.Length);
Array.Copy(padPlus, 0, paddedCipher, cipher.Length, blockSize);
//no reset passed in Rijndael
_tdcsp.Key = origKey;
_tdcsp.IV = origIv;
byte [] plain = _tdcsp.DecryptValue(paddedCipher);
return(plain);
}