using System;

using System.IO;

using System.Security.Cryptography;

using System.Text;

public class Program

{

    public static void Main()

    {

        var key = Security.KEY;

        var enc = Security.Encrypt("123", key);

        var dec = Security.Decrypt(enc, key);

        Console.WriteLine(enc);

        Console.WriteLine(dec);

    }

}

​

public static class Security

    {

        public static string KEY = "HELLO";

​

        public struct DESKeyPack

        {

            public byte[] Key, IV;

​

            public DESKeyPack(byte[] data)

            {

                Key = new byte[8];

                Buffer.BlockCopy(data, 0, Key, 0, 8);

                IV = new byte[8];

                Buffer.BlockCopy(data, 8, IV, 0, 8);

            }

        }

​

        private static DESKeyPack genKeyPack(string keyString)

        {

            //可以在不同的版本設不同的SALT值 //則不同版本的程式不能用來解密 

            const string salt = "SALT";

            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();

            byte[] data = md5.ComputeHash(UTF8Encoding.UTF8.GetBytes(keyString + salt));

            md5.Clear();

            DESKeyPack dkp = new DESKeyPack(data);

            return dkp;

        }

​

        /// <summary>

        /// 加密

        /// </summary>

        /// <param name="rawString"></param>

        /// <param name="keyString"></param>

        /// <returns></returns>

        public static string Encrypt(string rawString, string keyString)

        {

            DESKeyPack dkp = genKeyPack(keyString);

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            ICryptoTransform trans = des.CreateEncryptor(dkp.Key, dkp.IV);

            MemoryStream ms = new MemoryStream();

            CryptoStream cs = new CryptoStream(ms, trans, CryptoStreamMode.Write);

            byte[] rawData = UTF8Encoding.UTF8.GetBytes(rawString);

            cs.Write(rawData, 0, rawData.Length);

            cs.Close();

            return Convert.ToBase64String(ms.ToArray());

        }

​

        /// <summary>

        /// 解密

        /// </summary>

        /// <param name="encString"></param>

        /// <param name="keyString"></param>

        /// <returns></returns>

        public static string Decrypt(string encString, string keyString)

        {

            DESKeyPack dkp = genKeyPack(keyString);

            DESCryptoServiceProvider des = new DESCryptoServiceProvider();

            ICryptoTransform trans = des.CreateDecryptor(dkp.Key, dkp.IV);

            MemoryStream ms = new MemoryStream();

            CryptoStream cs = new CryptoStream(ms, trans, CryptoStreamMode.Write);

            byte[] rawData = Convert.FromBase64String(encString);

            cs.Write(rawData, 0, rawData.Length);

            cs.Close();

            return UTF8Encoding.UTF8.GetString(ms.ToArray());

        }

}