/// <summary>
/// Using this instances parameters, create a decryptor
/// </summary>
/// <returns>A new decrypting transformation instance</returns>
public override ICryptoTransform DecryptingTransform()
{
using (SymmetricAlgorithm aes = CreateAlgorithmInternal())
{
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.PKCS7;
return(aes.CreateDecryptingTransform());
}
}
/// <summary>
/// Decrypt in one operation.
/// </summary>
/// <param name="cipherText">The complete cipher text</param>
/// <returns>The decrypted result minus any padding</returns>
public override byte[] Decrypt(byte[] cipherText)
{
if (cipherText == null)
{
throw new ArgumentNullException("cipherText");
}
using (SymmetricAlgorithm aes = CreateAlgorithmInternal())
{
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.None;
using (ICryptoTransform decryptor = aes.CreateDecryptingTransform())
{
byte[] plaintext = decryptor.TransformFinalBlock(cipherText, 0, cipherText.Length);
return(plaintext);
}
}
}
public BlockAlgorithmKeyWrapTransform(SymmetricAlgorithm symmetricAlgorithm, Salt salt, KeyWrapDirection keyWrapDirection)
{
if (symmetricAlgorithm == null)
{
throw new ArgumentNullException("symmetricAlgorithm");
}
if (salt == null)
{
throw new ArgumentNullException("salt");
}
if (salt.Length != 0 && salt.Length < symmetricAlgorithm.Key().Length)
{
throw new InternalErrorException("Salt is too short. It must be at least as long as the algorithm key, or empty for no salt.");
}
_algorithm = symmetricAlgorithm;
byte[] saltedKey = _algorithm.Key();
saltedKey.Xor(salt.GetBytes().Reduce(saltedKey.Length));
_algorithm.SetKey(saltedKey);
_algorithm.Mode = CipherMode.ECB;
_algorithm.Padding = PaddingMode.None;
BlockLength = _algorithm.BlockSize / 8;
_transform = keyWrapDirection == KeyWrapDirection.Encrypt ? _algorithm.CreateEncryptingTransform() : _algorithm.CreateDecryptingTransform();
}
