[C#]加密解密源碼

using System;
using System.IO;
using System.Text;
using System.Security.Cryptography;

namespace xxxxxxxxxx
...{
    /**//// <summary>
    /// Crypto 的摘要說明。
    /// 採用Sington模式，系統中只能有一個副本
    /// </summary>
    public class Crypto
    ...{
        private static Crypto _instance=null;
        private SymmetricAlgorithm mobjCryptoService;
        private string r1,r2,r3,r4,r5;    //隨機產生5個0-9的數字
//        private int policy;

        private Crypto()
        ...{
            mobjCryptoService = new RijndaelManaged();
            r1="";
            r2="";
            r3="";
            r4="";
            r5="";
        }
        /**//// <summary>
        /// 獲取Crypto實例
        /// </summary>
        /// <returns></returns>
        public static Crypto Instance()
        ...{
            if(Crypto._instance==null)
            ...{
                Crypto._instance=new Crypto();
            }
            return Crypto._instance;
        }
        /**//// <summary>
        /// 對明文進行加密，返回加密後的密文
        /// </summary>
        /// <param name="source">密碼明文</param>
        /// <returns></returns>
        public string Cryp(string source)
        ...{
            int i,code=2,odd=-1;
            string result="";
            for(i=0;i<source.Trim().Length;i++)
            ...{
                code*=odd;
                result+=Convert.ToChar((int)Convert.ToChar(source.Trim().Substring(i,1))+code).ToString();
            }
            return result.Trim();
//            return source;
        }
        /**//// <summary>
        /// 對密文進行解密，返回明文
        /// </summary>
        /// <param name="cryptograph">密碼密文</param>
        /// <returns></returns>
        public string UnCryp(string cryptograph)
        ...{
            int i,code=-2,odd=-1;
            string result="";
            for(i=0;i<cryptograph.Trim().Length;i++)
            ...{
                code*=odd;
                result+=Convert.ToChar((int)Convert.ToChar(cryptograph.Trim().Substring(i,1))+code).ToString();
            }
            return result.Trim();
//            return cryptograph;
        }
        /**//// <summary>
        /// 獲得初始Key
        /// </summary>
        /// <returns></returns>
        private byte[] GetLegalKey()
        ...{
            string sTemp = "Guz(%"+r1+"&h7H$y"+r2+"04~FtT5&"+r3+"]@"+r4+"6*/["+r5+")7*/";
            mobjCryptoService.GenerateKey();
            byte[] bytTemp = mobjCryptoService.Key;
            int KeyLength = bytTemp.Length;
            if (sTemp.Length > KeyLength)
            ...{
                sTemp = sTemp.Substring(0, KeyLength);
            }
            else if (sTemp.Length < KeyLength)
            ...{
                sTemp = sTemp.PadRight(KeyLength, ' ');
            }
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /**//// <summary>
        /// 獲得初始向量IV
        /// </summary>
        /// <returns>初試向量IV</returns>
        private byte[] GetLegalIV()
        ...{
            string sTemp = "E"+r1+"r"+r2+"%r"+r3+"1$"+r4+"U^#@"+r5+"*";
            mobjCryptoService.GenerateIV();
            byte[] bytTemp = mobjCryptoService.IV;
            int IVLength = bytTemp.Length;
            if (sTemp.Length > IVLength)
            ...{
                sTemp = sTemp.Substring(0, IVLength);
            }
            else if (sTemp.Length < IVLength)
            ...{
                sTemp = sTemp.PadRight(IVLength, ' ');
            }
            return ASCIIEncoding.ASCII.GetBytes(sTemp);
        }
        /**//// <summary>
        /// 加密方法
        /// </summary>
        /// <param name="Source">待加密的串</param>
        /// <returns>經過加密的串</returns>
        public string Encrypto(string Source)
        ...{
            byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
            MemoryStream ms = new MemoryStream();
            //隨機產生5個0-9之間的數字，然後插入初始Key的固定部分
            r1=Convert.ToString((int)((new Random()).NextDouble()*2));
            r2=Convert.ToString((int)((new Random()).NextDouble()*2));
            r3=Convert.ToString((int)((new Random()).NextDouble()*2));
            r4=Convert.ToString((int)((new Random()).NextDouble()*2));
            r5=Convert.ToString((int)((new Random()).NextDouble()*2));
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
            cs.Write(bytIn, 0, bytIn.Length);
            cs.FlushFinalBlock();
            ms.Close();
            byte[] bytOut = ms.ToArray();
            return Convert.ToBase64String(bytOut)+Cryp(r1+r2+r3+r4+r5);
        }
        /**//// <summary>
        /// 解密方法
        /// </summary>
        /// <param name="Source">待解密的串</param>
        /// <returns>經過解密的串</returns>
        public string Decrypto(string Source)
        ...{
            int len=Source.Length;
            string rString=UnCryp(Source.Substring(len-5,5));
            r1=rString.Substring(0,1);
            r2=rString.Substring(1,1);
            r3=rString.Substring(2,1);
            r4=rString.Substring(3,1);
            r5=rString.Substring(4,1);
            byte[] bytIn = Convert.FromBase64String(Source.Substring(0,len-5));
            MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
            mobjCryptoService.Key = GetLegalKey();
            mobjCryptoService.IV = GetLegalIV();
            ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
            CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
            StreamReader sr = new StreamReader(cs);
            return sr.ReadToEnd();
        }