/// <summary>
/// Decrypts data encrypted using <see cref="Encrypt(SymmetricKey,byte[],int)" />.
/// </summary>
/// <param name="symmetricKey">The symmetric algorithm arguments.</param>
/// <param name="cipherText">The encrypted data.</param>
/// <returns>The decrypted result.</returns>
public static byte[] Decrypt(SymmetricKey symmetricKey, byte[] cipherText)
{
EnhancedMemoryStream input = new EnhancedMemoryStream(cipherText);
EnhancedMemoryStream ms = new EnhancedMemoryStream(cipherText.Length);
BlockDecryptor decryptor = null;
try
{
// Read the header fields
if (input.ReadInt32() != Magic)
{
throw new CryptographicException(BadFormatMsg);
}
if (input.ReadInt32() != 0)
{
throw new CryptographicException("Unsupported secure data format version.");
}
decryptor = new BlockDecryptor(symmetricKey);
// Decrypt the contents
ms.WriteBytesNoLen(decryptor.Decrypt(input.ReadBytes32()));
ms.Position = 0;
if (ms.ReadInt32() != Magic)
{
throw new CryptographicException("Secure data content is corrupt.");
}
ms.Position += 8; // Skip over the salt
return(ms.ReadBytes32());
}
finally
{
if (decryptor != null)
{
decryptor.Dispose();
}
input.Close();
ms.Close();
}
}
/// <summary>
/// Decrypts a byte array encrypted using <see cref="Encrypt(string ,byte[],string,int,int,out SymmetricKey)" />.
/// </summary>
/// <param name="rsaKey">The decrypting RSA key as XML or as a secure key container name.</param>
/// <param name="cipherText">The encrypted data.</param>
/// <param name="symmetricKey">Returns as the symmetric encryption algorithm arguments.</param>
/// <returns>The decrypted data.</returns>
/// <exception cref="CryptographicException">Thrown is the encrypted data block is incorrectly formatted.</exception>
/// <remarks>
/// Note that applications should take some care to ensure that the <paramref name="symmetricKey" />
/// value return is disposed so that the symmetric encryption key will be cleared.
/// </remarks>
public static byte[] Decrypt(string rsaKey, byte[] cipherText, out SymmetricKey symmetricKey)
{
EnhancedMemoryStream input = new EnhancedMemoryStream(cipherText);
EnhancedMemoryStream ms = new EnhancedMemoryStream(cipherText.Length);
BlockDecryptor decryptor = null;
byte[] symKey;
byte[] symIV;
string algorithm;
try
{
// Read the header fields
if (input.ReadInt32() != Magic)
{
throw new CryptographicException(BadFormatMsg);
}
if (input.ReadInt32() != 0)
{
throw new CryptographicException("Unsupported secure data format version.");
}
// Decrypt the encryption info
ms.WriteBytesNoLen(AsymmetricCrypto.Decrypt(CryptoAlgorithm.RSA, rsaKey, input.ReadBytes16()));
ms.Position = 0;
algorithm = ms.ReadString16();
symKey = ms.ReadBytes16();
symIV = ms.ReadBytes16();
symmetricKey = new SymmetricKey(algorithm, symKey, symIV);
decryptor = new BlockDecryptor(algorithm, symKey, symIV);
// Decrypt the contents
ms.SetLength(0);
ms.WriteBytesNoLen(decryptor.Decrypt(input.ReadBytes32()));
ms.Position = 0;
if (ms.ReadInt32() != Magic)
{
throw new CryptographicException("Secure data content is corrupt.");
}
ms.Position += 8; // Skip over the salt
return(ms.ReadBytes32());
}
finally
{
if (decryptor != null)
{
decryptor.Dispose();
}
input.Close();
ms.Close();
}
}
