原文链接：http://www.cnblogs.com/hakuci/archive/2008/03/23/1118545.html 本文讲 ASP.NET的MD5和DES加密和解密算法
#region MD5算法
        public string md5(string str, int code)
        {
            if (code == 16) //16位MD5加密（取32位加密的9~25字符） 
            {
                return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower().Substring(8, 16);
            }
            if (code == 32) //32位加密 
            {
                return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "MD5").ToLower();
            }
            return "00000000000000000000000000000000";
        }
        #endregion

        #region DESEncrypt DES加密
        // <summary>
        /// 进行DES加密。
        /// </summary>
        /// <param name="pToEncrypt">要加密的字符串。</param>
        /// <param name="sKey">密钥，且必须为8位。</param>
        /// <returns>以Base64格式返回的加密字符串。</returns>
        public string DESEncrypt(string pToEncrypt, string sKey)
        {
            using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
            {
                byte[] inputByteArray = Encoding.UTF8.GetBytes(pToEncrypt);
                des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
                des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                using (CryptoStream cs = new CryptoStream(ms, des.CreateEncryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(inputByteArray, 0, inputByteArray.Length);
                    cs.FlushFinalBlock();
                    cs.Close();
                }
                string str = Convert.ToBase64String(ms.ToArray());
                ms.Close();
                return str;
            }
        }
        #endregion

        #region DESDecrypt DES解密
        /// <summary>
        /// 进行DES解密。
        /// </summary>
        /// <param name="pToDecrypt">要解密的以Base64</param>
        /// <param name="sKey">密钥，且必须为8位。</param>
        /// <returns>已解密的字符串。</returns>
        public string DESDecrypt(string pToDecrypt, string sKey)
        {
            byte[] inputByteArray = Convert.FromBase64String(pToDecrypt);
            using (DESCryptoServiceProvider des = new DESCryptoServiceProvider())
            {
                des.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
                des.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                using (CryptoStream cs = new CryptoStream(ms, des.CreateDecryptor(), CryptoStreamMode.Write))
                {
                    cs.Write(inputByteArray, 0, inputByteArray.Length);
                    cs.FlushFinalBlock();
                    cs.Close();
                }
                string str = Encoding.UTF8.GetString(ms.ToArray());
                ms.Close();
                return str;
            }
        }
        #endregion

转载于:https://www.cnblogs.com/hakuci/archive/2008/03/23/1118545.html