C# 加密算法

 public static class Common

    {

        #region MD5加密

        /// <summary>   

        /// MD5加密   

        /// </summary>   

        /// <param name="strSource">需要加密的字符串</param>   

        /// <returns>MD5加密后的字符串</returns>   

        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();

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

        }

        /// <summary>   

        /// MD5解密   

        /// </summary>   

        /// <param name="Source">需要解密的字符串</param>   

        /// <returns>MD5解密后的字符串</returns>   

        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();

        }

        #endregion

        #region 动态加密

        private static byte[] s_bytKey;

        static Common()

        {

            s_bytKey = new byte[] { 0xa1, 0xb2, 0xc3, 0xd4, 0xe5, 0x16, 0x27, 0x38, 0x49, 80, 0x61, 0x72, 0x83, 0x94, 0xa5, 0xb6 };

        }

        /// <summary>

        /// 解密

        /// </summary>

        /// <param name="text"></param>

        /// <param name="key"></param>

        /// <returns></returns>

        public static string PutBykey(string text, string key)

        {

            byte[] buffer = new byte[text.Length];

            byte[] bytes = Encoding.UTF8.GetBytes(Dscf.Global.Common.Common.DisposeId(key));

            RijndaelManaged managed = new RijndaelManaged();

            buffer = Convert.FromBase64String(text);

            MemoryStream stream = new MemoryStream();

            CryptoStream stream2 = new CryptoStream(stream, managed.CreateDecryptor(bytes, s_bytKey), CryptoStreamMode.Write);

            stream2.Write(buffer, 0, buffer.Length);

            stream2.FlushFinalBlock();

            Encoding encoding = new UTF8Encoding();

            return encoding.GetString(stream.ToArray());

        }

        /// <summary>

        /// 加密

        /// </summary>

        /// <param name="text"></param>

        /// <param name="key"></param>

        /// <returns></returns>

        public static string GetByKey(string text, string key)

        {

            byte[] bytes = Encoding.UTF8.GetBytes(text);

            byte[] rgbKey = Encoding.UTF8.GetBytes(Dscf.Global.Common.Common.DisposeId(key));

            RijndaelManaged managed = new RijndaelManaged();

            MemoryStream stream = new MemoryStream();

            CryptoStream stream2 = new CryptoStream(stream, managed.CreateEncryptor(rgbKey, s_bytKey), CryptoStreamMode.Write);

            stream2.Write(bytes, 0, bytes.Length);

            stream2.FlushFinalBlock();

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

        }

        /// <summary>

        /// 处理Id，转变为加密key

        /// </summary>

        /// <param name="id"></param>

        /// <returns></returns>

        public static string DisposeId(string id)

        {

            string strValue = "";

            for (int i = 0; i < 9 - id.Length; i++)

            {

                strValue += i;

            }

            return id.ToString() + strValue;

        }

        #endregion

    }