StringCipher.cs

// taken from here:
// http://stackoverflow.com/questions/10168240/encrypting-decrypting-a-string-in-c-sharp

namespace TextManipulationUtility
{
    using System;
    using System.Diagnostics.CodeAnalysis;
    using System.IO;
    using System.Security.Cryptography;
    using System.Text;

    public static class StringCipher
    {
        // This constant string is used as a "salt" value for the PasswordDeriveBytes function calls.
        // This size of the IV (in bytes) must = (keysize / 8).  Default keysize is 256, so the IV must be
        // 32 bytes long.  Using a 16 character string here gives us 32 bytes when converted to a byte array.
        private const string InitVector = "90ut89eui24gj8t3";

        // This constant is used to determine the keysize of the encryption algorithm.
        private const int Keysize = 256;

        [SuppressMessage("Microsoft.Usage", "CA2202:Do not dispose objects multiple times")]
        public static string Encrypt(string plainText, string passPhrase)
        {
            byte[] initVectorBytes = Encoding.UTF8.GetBytes(InitVector);
            byte[] plainTextBytes = Encoding.UTF8.GetBytes(plainText);
            PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
            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();
            return Convert.ToBase64String(cipherTextBytes);
        }

        [SuppressMessage("Microsoft.Usage", "CA2202:Do not dispose objects multiple times")]
        public static string Decrypt(string cipherText, string passPhrase)
        {
            byte[] initVectorBytes = Encoding.ASCII.GetBytes(InitVector);
            byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
            PasswordDeriveBytes password = new PasswordDeriveBytes(passPhrase, null);
            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();
            return Encoding.UTF8.GetString(plainTextBytes, 0, decryptedByteCount);
        }
    }
}