/// <summary>
/// Gets a SymmetricAlgorithm's transformer.
/// </summary>
/// <param name="cipher">The SymmetricAlgorithm.</param>
/// <param name="transformMode">The get the encrypt/decrypt transformer.</param>
/// <returns>The SymmetricAlgorithm's transformer.</returns>
private static ICryptoTransform GetTransformer(SymmetricAlgorithm cipher, CipherTransformMode transformMode)
{
if (transformMode == CipherTransformMode.Encrypt)
{
// Get an encryptor.
return(cipher.CreateEncryptor());
}
// Get an decryptor.
return(cipher.CreateDecryptor());
}
/// <summary>
/// Encrypts or decrypts a stream.
/// </summary>
/// <param name="cipher">The cipher to use.</param>
/// <param name="transformMode">Defines the way in which the cipher will work.</param>
/// <param name="input">The input stream.</param>
/// <param name="output">The output stream.</param>
public static void SymmetricTransform(SymmetricAlgorithm cipher, CipherTransformMode transformMode, Stream input, Stream output)
{
if (cipher == null)
{
throw new ArgumentNullException(nameof(cipher));
}
using ICryptoTransform transformer = GetTransformer(cipher, transformMode);
using StreamReader reader = new(input, new UnicodeEncoding());
reader.Peek();
// Create a CryptoStream using the FileStream and the passed key and initialization vector (IV).
using CryptoStream crypto = new(output, transformer, CryptoStreamMode.Write);
byte[] bytes;
// The cipher is expecting Unicode
while (!reader.EndOfStream)
{
bytes = reader.CurrentEncoding.GetBytes(new char[] { (char)reader.Read() });
crypto.Write(bytes, 0, bytes.Length);
}
}
/// <summary>
/// Enciphers or deciphers a string.
/// </summary>
/// <param name="cipher">The cipher to use.</param>
/// <param name="transformMode">Defines the way in which the cipher will work.</param>
/// <param name="input">The input text.</param>
/// <returns>The output text.</returns>
/// <exception cref="ArgumentNullException"> Thrown if <paramref name="cipher" /> is null.</exception>
/// <exception cref="NotImplementedException"> Thrown sometimes.</exception>
public static string SymmetricTransform(SymmetricAlgorithm cipher, CipherTransformMode transformMode, string input)
{
if (cipher == null)
{
throw new ArgumentNullException(nameof(cipher));
}
Encoding encoding = new UnicodeEncoding();
using ICryptoTransform cryptoTransform = GetTransformer(cipher, transformMode);
// Encrypt the data.
using MemoryStream inputStream = new(encoding.GetBytes(input));
using MemoryStream outputStream = new();
SymmetricTransform(cipher, transformMode, inputStream, outputStream);
// Remove padding on odd length bytes
byte[] encrypted = cryptoTransform.OutputBlockSize % 2 == 1 ? TrimArray(outputStream.ToArray()) : outputStream.ToArray();
char[] encryptedChars = encoding.GetChars(encrypted);
return(new string(encryptedChars));
}
internal ClassicalSymmetricTransform(ICipher cipher, CipherTransformMode transformMode)
{
_transformMode = transformMode;
Cipher = cipher;
}