/// <summary>
/// Method for decrypting to text
/// </summary>
/// <param name="selectedAlgorithim">the algorithim to use, will be cast to enum</param>
/// <param name="keySize">the key size to use</param>
/// <param name="secretKey">the secret key for the algorithim</param>
/// <param name="encrypted">the encrypted bytes</param>
/// <returns>decrypted text</returns>
public string DecryptToText(int selectedAlgorithim, int keySize, byte[] secretKey, byte[] iv, byte[] encrypted)
{
var algorithim = ((SymmetricBouncyCastleCipher)selectedAlgorithim).ToString().Replace("_", "-");;
bufferedCipher = CipherUtilities.GetCipher(algorithim);
if (GetIvSize(selectedAlgorithim) > 0)
{
var kp = new KeyParameter(secretKey);
var ivp = new ParametersWithIV(kp, iv);
bufferedCipher.Init(false, ivp);
}
else
{
bufferedCipher.Init(false, new KeyParameter(secretKey));
}
byte[] decrypted = null;
try
{
decrypted = bufferedCipher.DoFinal(encrypted);
}
catch (CryptoException exception)
{
if (exception.Message == "pad block corrupted")
{
string message = "Decryption failed!\n" +
"The secret key is corrupted.\n" +
"Verify that the same key is used for encrypting and decrypting.";
throw new CryptoException(message, exception);
}
else if (exception.Message == "last block incomplete in decryption")
{
string message = "Decryption failed!\n" +
"The encryption block length is not complete\n" +
"Verify that the encryption bit length is a multiple of the expected blocksize\n" +
$"Blocksize bit length: {bufferedCipher.GetBlockSize() * 8}\n" +
$"Encryption bit length: {encrypted.Length * 8}";
throw new CryptoException(message, exception);
}
else
{
throw new CryptoException("Contact developer for help.", exception);
}
}
return(ByteConvert.BytesToUTF8String(decrypted));
}
/// <summary>
/// Decrypts the encrypted byte array to a plain text
/// </summary>
/// <param name="privateKey">the private key used for decryption</param>
/// <param name="encrypted">the encrypted bytes</param>
/// <returns>the decrypted plain text</returns>
public string DecryptToText(byte[] privateKey, byte[] encrypted)
{
var decrypted = DecryptToBytes(privateKey, encrypted);
return(ByteConvert.BytesToUTF8String(decrypted));
}
