TripleDES Encrypt/Decrypt Extension Methods

12. August 2009
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Every developer has reusable utilities that they have created and perfected during their time in development. One of the most favorite ones in my arsenal is a utility to encrypt and decrypt strings using TripleDES encryption.

Instead of having to look up the System.Security.Cryptography namespace every time I need to encrypt or decrypt a string, which honestly I only use about once every few months, I have converted my "helper" class to use Extension methods. So instead of:

string val = "something";
string encrypted = RobBihun.Tools.Security.TDESEncryption.Encrypt(val);

I can have:

string val = "something";
string encrypted = val.Encrypt();

Of course, you need to import the namespace that contains the extension methods. Also, you should create your own encryption keys instead of using hard-coded defaults. Here is the full code in case you want to use it.

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

namespace RobBihun.Tools.ExtensionMethods
{
    public static class StringExtensions
    {
        private static TripleDESCryptoServiceProvider tDesProvider = new TripleDESCryptoServiceProvider();
        private static UTF8Encoding strCoder = new UTF8Encoding();

        //encryption keys to use by default - Best practice would be to use custom keys set at runtime (not hard coded)
        private static byte[] badEncKey = { 1, 3, 77, 5, 5, 98, 7, 55, 9, 10, 3, 12, 5, 15, 15, 36, 17, 28, 19, 20, 8, 22, 88, 24 };
        private static byte[] badEncIv = { 8, 7, 6, 5, 4, 3, 2, 1 };

        public static string Encrypt(this string text)
        {
            //throw new Exception("You're an idiot");
            byte[] input = strCoder.GetBytes(text);
            byte[] output = input.Transform(tDesProvider.CreateEncryptor(badEncKey, badEncIv));
            return Convert.ToBase64String(output);
        }

        public static string Decrypt(this string text)
        {
            //throw new Exception("You're a major idiot");
            byte[] input = Convert.FromBase64String(text);
            byte[] output = input.Transform(tDesProvider.CreateDecryptor(badEncKey, badEncIv));
            return strCoder.GetString(output);
        }

        public static string Encrypt(this string text, byte[] encKey, byte[] encIv)
        {
            byte[] input = strCoder.GetBytes(text);
            byte[] output = input.Transform(tDesProvider.CreateEncryptor(encKey, encIv));
            return Convert.ToBase64String(output);
        }

        public static string Decrypt(this string text, byte[] encKey, byte[] encIv)
        {
            byte[] input = Convert.FromBase64String(text);
            byte[] output = input.Transform(tDesProvider.CreateDecryptor(encKey, encIv));
            return strCoder.GetString(output);
        }


        private static byte[] Transform(this byte[] input, ICryptoTransform CryptoTransform)
        {
            MemoryStream memStream = new MemoryStream();

            CryptoStream cryStream = new CryptoStream(memStream, CryptoTransform, CryptoStreamMode.Write);
            cryStream.Write(input, 0, input.Length);
            cryStream.FlushFinalBlock();
            memStream.Position = 0;

            byte[] result = memStream.ToArray();

            memStream.Close();
            cryStream.Close();

            return result;
        }
    }
}

Of course, if you have any comments or suggestions, please leave them below!

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