/// <summary>
/// Utility to encapsulate round-tripping ciphertext
/// </summary>
private static bool RoundTripHelper(Type encryptionAlgorithm,
Action <SymmetricAlgorithm> encryptionSetup,
Type decryptionAlgorithm,
Action <SymmetricAlgorithm> decryptionSetup)
{
// Encryption parameters
byte[] key = null;
byte[] iv = null;
CipherMode cipherMode = CipherMode.CBC;
PaddingMode paddingMode = PaddingMode.None;
// Round tripping data
byte[] plainText = Encoding.UTF8.GetBytes("Secret round trip message");
byte[] cipherText = null;
SymmetricEncryptionState encryptionState = null;
SymmetricAlgorithm encryptionObject = null;
try
{
// Setup the encryption algorithm
encryptionObject = (SymmetricAlgorithm)Activator.CreateInstance(encryptionAlgorithm);
encryptionSetup(encryptionObject);
encryptionObject = encryptionObject.EnableLogging();
// Encrypt the data
using (MemoryStream ms = new MemoryStream())
using (CryptoStream cs = new CryptoStream(ms, encryptionObject.CreateEncryptor(), CryptoStreamMode.Write))
{
cs.Write(plainText, 0, plainText.Length);
cs.FlushFinalBlock();
cipherText = ms.ToArray();
}
// Save the encryption parameters
key = encryptionObject.Key;
iv = encryptionObject.IV;
cipherMode = encryptionObject.Mode;
paddingMode = encryptionObject.Padding;
encryptionState = encryptionObject.GetLastEncryptionState();
}
finally
{
if (encryptionObject != null)
{
(encryptionObject as IDisposable).Dispose();
}
}
byte[] roundTrip = null;
// Now verify the data
SymmetricAlgorithm decryptionObject = null;
try
{
decryptionObject = (SymmetricAlgorithm)Activator.CreateInstance(decryptionAlgorithm);
decryptionObject.Key = key;
decryptionObject.IV = iv;
decryptionObject.Mode = cipherMode;
decryptionObject.Padding = paddingMode;
decryptionSetup(decryptionObject);
decryptionObject = decryptionObject.EnableDecryptionVerification(encryptionState);
using (MemoryStream ms = new MemoryStream())
using (CryptoStream cs = new CryptoStream(ms, decryptionObject.CreateDecryptor(), CryptoStreamMode.Write))
{
cs.Write(cipherText, 0, cipherText.Length);
cs.FlushFinalBlock();
roundTrip = ms.ToArray();
}
}
finally
{
if (decryptionObject != null)
{
(decryptionObject as IDisposable).Dispose();
}
}
if (roundTrip.Length != plainText.Length)
{
return(false);
}
for (int i = 0; i < roundTrip.Length; ++i)
{
if (roundTrip[i] != plainText[i])
{
return(false);
}
}
return(true);
}
