/// <summary>
/// Decrypts a string that was encrypted using RijndalAES algorithm with the specified post-encryption encoding.
/// </summary>
/// <param name="data">Encrypted data generated from EncryptData method.</param>
/// <param name="password">Password used to decrypt the string.</param>
/// <param name="characterEncoding">
/// Determines what the post encryption encoding of <paramref name="data"/> is.
/// When encrypting, this value needs to be exactly the same as used for decryption.
/// </param>
/// <param name="applySalt">
/// Determines whether the key is salted (transformed) before being used for extra security against brute force attacks.
/// When encrypting, this value needs to be exactly the same as used for decryption.
/// </param>
/// <returns>Decrypted string.</returns>
/// <exception cref="ArgumentNullException">If <paramref name="data"/> or <paramref name="password"/> is null.</exception>
/// <exception cref="Exception">If the decryption fails for any reason.</exception>
public static string Decrypt(string password, string data, Encoding.CharacterEncoding characterEncoding, bool applySalt)
{
if (data == null)
{
throw new ArgumentNullException("data");
}
if (password == null)
{
throw new ArgumentNullException("password");
}
string decodedString = null;
try
{
byte[] encBytes;
switch (characterEncoding)
{
case Encoding.CharacterEncoding.Base64:
encBytes = Convert.FromBase64String(data);
break;
case Encoding.CharacterEncoding.Hex:
encBytes = HexUtil.GetBytes(data);
break;
default:
encBytes = System.Text.Encoding.GetEncoding(1252).GetBytes(data);
break;
}
byte[] decBytes = DecryptData(encBytes, password, PaddingMode.ISO10126, applySalt);
decodedString = System.Text.Encoding.GetEncoding(1252).GetString(decBytes);
//When salting, remove the datetime we added at the end of the string.
if (applySalt)
{
decodedString = decodedString.Substring(0, decodedString.Length - 19);
}
}
catch (Exception ex)
{
throw new Exception("The encrypted string was not in a valid format.", ex);
}
return(decodedString);
}
/// <summary>
/// Use AES to encrypt data string and optionally encode it afterwards.
/// The same <paramref name="password"/> and <see cref="Salt"/> must be used to decrypt the string.
/// </summary>
/// <param name="data">Clear string to encrypt.</param>
/// <param name="password">Password used to encrypt the string.</param>
/// <param name="characterEncoding">
/// Determines what the post encryption encoding of <paramref name="data"/> is.
/// Setting this value to anything but <see cref="CharacterEncoding.None"/> will encode the resulting
/// encrypted value with the specified encoding.
/// When encrypting, this value needs to be exactly the same as used for decryption.
/// </param>
/// <param name="applySalt">
/// Determines whether the key is salted (transformed) before being used for extra security against brute force attacks.
/// When decrypting, this value needs to be exactly the same as used for encryption.
/// </param>
/// <returns>Encrypted result encode as specified in <paramref name="characterEncoding"/>.</returns>
/// <exception cref="ArgumentNullException">If <paramref name="data"/> or <paramref name="password"/> is null.</exception>
public static string Encrypt(string password, string data, Encoding.CharacterEncoding characterEncoding, bool applySalt)
{
if (data == null)
{
throw new ArgumentNullException("data");
}
if (password == null)
{
throw new ArgumentNullException("password");
}
//In addition to applying a salt value, we're also changing the data by appending the datetime. This will be truncated
//when decrypting but just makes the encryption a bit more random.
if (applySalt)
{
data += DateTime.Now.ToString("dd MM yyyy HH:mm:ss");
}
byte[] encBytes = EncryptData(System.Text.Encoding.GetEncoding(1252).GetBytes(data), password, PaddingMode.ISO10126, applySalt);
string retVal = string.Empty;
switch (characterEncoding)
{
case Encoding.CharacterEncoding.Base64:
retVal = Convert.ToBase64String(encBytes);
break;
case Encoding.CharacterEncoding.Hex:
retVal = HexUtil.ToString(encBytes);
break;
default:
retVal = System.Text.Encoding.GetEncoding(1252).GetString(encBytes);
break;
}
return(retVal);
}
