【共用】.net加解密函數匯總

using System;
using System.Web.Security;
using System.Text;
using System.Security.Cryptography;

namespace EncryptAndDecode
{
    /// <summary>
    /// Functions 的摘要說明。
    /// </summary>
    public class EncryptAndDecode
    {
        public EncryptAndDecode()
        {
            //
            // TODO: 在此處添加建構函式邏輯
            //
        }

        #region Encrypt 單向加密函數
        /// <summary>
        /// 加密函數
        /// </summary>
        /// <param name="PasswordString">待加密的字串</param>
        /// <param name="PasswordFormat">加密的方式</param>
        /// <returns></returns>
        public static string Encrypt(string PasswordString,string PasswordFormat)
        {
            string EncryptPassword;

            if (PasswordFormat.ToUpper() =="SHA1")
            {
    　　        EncryptPassword=FormsAuthentication.HashPasswordForStoringInConfigFile(PasswordString ,"SHA1");
            }
            else if (PasswordFormat=="MD5")
            {
    　　        EncryptPassword=FormsAuthentication.HashPasswordForStoringInConfigFile(PasswordString ,"MD5");
            }
            else
            {
    　　        EncryptPassword="";
            }

            return EncryptPassword;
        }
        #endregion
        
        #region Encode 可逆加密解密函數
        /// <summary>
        /// 加密函數
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string Encode(string str)
        {            
            int i=0;
            StringBuilder sb = new StringBuilder();
            
            foreach(char a in str)
            {                        
                switch(i % 5)
                {
                    case 0:
                        sb.Append((char)(a+1));
                        break;
                    case 1:
                        sb.Append((char)(a+2));
                        break;
                    case 2:
                        sb.Append((char)(a+3));
                        break;
                    case 3:
                        sb.Append((char)(a+4));
                        break;
                    case 4:
                        sb.Append((char)(a+5));
                        break;
                }
                i++;
            }

            return sb.ToString();
        }

        /// <summary>
        /// 解密函數
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static string Decode(string str)
        {            
            int i=0;
            StringBuilder sb = new StringBuilder();
            
            foreach(char a in str)
            {                        
                switch(i % 5)
                {
                    case 0:
                        sb.Append((char)(a-1));
                        break;
                    case 1:
                        sb.Append((char)(a-2));
                        break;
                    case 2:
                        sb.Append((char)(a-3));
                        break;
                    case 3:
                        sb.Append((char)(a-4));
                        break;
                    case 4:
                        sb.Append((char)(a-5));
                        break;
                }
                i++;
            }

            return sb.ToString();
        }
    
        #endregion

        /// <summary>
        ///  md5加密字串
        /// </summary>
        /// <param name="source">源字串</param>
        /// <param name="key">密鑰</param>
        /// <returns>加密後的字串</returns>
        public static string Encode(string source, string key)
        {
            MD5 md5 = new MD5CryptoServiceProvider();

            ASCIIEncoding code = new ASCIIEncoding();
            string str = source + key.ToLower();
            byte[] bit = code.GetBytes(str);

            str = Convert.ToBase64String(bit);
            bit = code.GetBytes(str);
            bit = md5.ComputeHash(bit);
            str = Convert.ToBase64String(bit);

            return str;
        }
    }
}