MD5加（解）密代码实现

public static string Md5Encrypt(string strSource)
        {
            //把字符串放到byte数组中  
            byte[] bytIn = System.Text.Encoding.Default.GetBytes(strSource);
            //建立加密对象的密钥和偏移量          
            byte[] iv = { 102, 16, 93, 156, 78, 4, 218, 32 };//定义偏移量  
            byte[] key = { 55, 103, 246, 79, 36, 99, 167, 3 };//定义密钥  
            //实例DES加密类  
            DESCryptoServiceProvider mobjCryptoService = new DESCryptoServiceProvider();
            mobjCryptoService.Key = iv;
            mobjCryptoService.IV = key;
            ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
            //实例MemoryStream流加密密文件  
            System.IO.MemoryStream ms = new System.IO.MemoryStream();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
            cs.Write(bytIn, 0, bytIn.Length);
            cs.FlushFinalBlock();

            string strOut = System.Convert.ToBase64String(ms.ToArray());
            return strOut;
        }

        public static string Md5Decrypt(string Source)
        {
            //将解密字符串转换成字节数组  
            byte[] bytIn = System.Convert.FromBase64String(Source);
            //给出解密的密钥和偏移量，密钥和偏移量必须与加密时的密钥和偏移量相同  
            byte[] iv = { 102, 16, 93, 156, 78, 4, 218, 32 };//定义偏移量  
            byte[] key = { 55, 103, 246, 79, 36, 99, 167, 3 };//定义密钥  
            DESCryptoServiceProvider mobjCryptoService = new DESCryptoServiceProvider();
            mobjCryptoService.Key = iv;
            mobjCryptoService.IV = key;
            //实例流进行解密  
            System.IO.MemoryStream ms = new System.IO.MemoryStream(bytIn, 0, bytIn.Length);
            ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
            StreamReader strd = new StreamReader(cs, Encoding.Default);
            return strd.ReadToEnd();
        }

控制台测试：

string sec = "ID=sa;Password=123456;";
            string md5 = Md5Encrypt(sec);
            string final = Md5Decrypt(md5);
            Console.WriteLine("加密前：" + sec + ",加密后：" + md5 + ",解密后：" + final);
            Console.ReadLine();

输出如下：