Uses of a symmetric key algorithm (Rijndael) to encrypt and decrypt data.

EXAMPLE: Symmetric key encryption and decryption using Rijndael algorithm.

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

public class RijndaelSimple
{
public static string Encrypt(string plainText,
string passPhrase,
string saltValue,
string hashAlgorithm,
int passwordIterations,
string initVector,
int keySize)
{
byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);

byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);

PasswordDeriveBytes password = new PasswordDeriveBytes(
passPhrase, saltValueBytes, hashAlgorithm,
passwordIterations);

byte[] keyBytes = password.GetBytes(keySize / 8);

RijndaelManaged symmetricKey = new RijndaelManaged();

symmetricKey.Mode = CipherMode.CBC;

ICryptoTransform encryptor = symmetricKey.CreateEncryptor(
keyBytes, initVectorBytes);

MemoryStream memoryStream = new MemoryStream();
CryptoStream cryptoStream = new CryptoStream(memoryStream,
encryptor, CryptoStreamMode.Write);
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);

cryptoStream.FlushFinalBlock();

byte[] cipherTextBytes = memoryStream.ToArray();

memoryStream.Close();
cryptoStream.Close();

string cipherText = Convert.ToBase64String(cipherTextBytes);

return cipherText;
}


public static string Decrypt(string cipherText,
string passPhrase, string saltValue, string hashAlgorithm,
int passwordIterations, string initVector, int keySize)
{

byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
PasswordDeriveBytes password = new PasswordDeriveBytes(
passPhrase, saltValueBytes, hashAlgorithm,
passwordIterations);

byte[] keyBytes = password.GetBytes(keySize / 8);
RijndaelManaged symmetricKey = new RijndaelManaged();
symmetricKey.Mode = CipherMode.CBC;
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(
keyBytes,
initVectorBytes);


MemoryStream memoryStream = new MemoryStream(cipherTextBytes);

CryptoStream cryptoStream = new CryptoStream(memoryStream,
decryptor, CryptoStreamMode.Read);
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
int decryptedByteCount = cryptoStream.Read(plainTextBytes,
0, plainTextBytes.Length);
memoryStream.Close();
cryptoStream.Close();

string plainText = Encoding.UTF8.GetString(plainTextByteis,
0,
decryptedByteCount);
return plainText;
}
}

public class RijndaelSimpleTest
{
static void Main(string[] args)
{
string plainText = "Hello, World!";

string passPhrase = "Pas5pr@se";
string saltValue = "s@1tValue";
string hashAlgorithm = "SHA1";
int passwordIterations = 2;
string initVector = "@1B2c3D4e5F6g7H8";
int keySize = 256;
Console.WriteLine(String.Format("Plaintext : {0}", plainText));
string cipherText = RijndaelSimple.Encrypt(plainText,
passPhrase,
saltValue,
hashAlgorithm,
passwordIterations,
initVector,
KeySize);

Console.WriteLine(String.Format("Encrypted : {0}", cipherText));

plainText = RijndaelSimple.Decrypt(cipherText,
passPhrase,
saltValue,
hashAlgorithm,
passwordIterations,
initVector,
keySize);

Console.WriteLine(String.Format("Decrypted : {0}", plainText));
}
}