代码整理：字符串编码解码类

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

namespace BTTech.WebModules
{
    /// <summary>
    /// 字符串加密
    /// </summary>
    public class SecurityUtility
    {
        #region 静态属性
        private static string m_iv = "        ";
        private static string m_key = "        ";
        #endregion

        #region RC2Encrypt
        public static string RC2Encrypt( string source , string key, string iv) 
        { 
            byte[] orgText = Encoding.UTF8.GetBytes(source);
            byte[] encryptText; 
            RC2CryptoServiceProvider myRC2=new RC2CryptoServiceProvider(); 
            ICryptoTransform myCryptoTrans=myRC2.CreateEncryptor(
                Encoding.UTF8.GetBytes( (key + m_key).Substring(0,8) ),
                Encoding.UTF8.GetBytes( (iv + m_iv).Substring(0,8) )
                ); 
            MemoryStream MStream=new MemoryStream(); 
            CryptoStream CStream=new CryptoStream(MStream,myCryptoTrans,CryptoStreamMode.Write); 
            CStream.Write(orgText,0,orgText.Length); 
            CStream.FlushFinalBlock(); 
            StringBuilder EnText=new StringBuilder(); 
            encryptText=MStream.ToArray(); 
            foreach(byte Byte in encryptText) 
            { 
                EnText.AppendFormat("{0:x2}",Byte); 
            } 
            CStream.Close(); 
            return EnText.ToString(); 
        } 
        #endregion

        #region RC2Decrypt
        public static string RC2Decrypt( string source , string key ,string iv) 
        { 
            byte[] encryptText = new byte[source.Length / 2]; 
            for(int Count = 0; Count < source.Length; Count+=2) 
            { 
                encryptText[Count/2] = (byte)(Convert.ToInt32(source.Substring(Count , 2), 16)); 
            } 
            
            byte[] decryptText;
            RC2CryptoServiceProvider myRC2=new RC2CryptoServiceProvider(); 
            ICryptoTransform myCryptoTrans=myRC2.CreateDecryptor(
                Encoding.UTF8.GetBytes( (key + m_key).Substring(0,8) ),
                Encoding.UTF8.GetBytes( (iv + m_iv).Substring(0,8) )
                ); 
            
            MemoryStream MStream=new MemoryStream(encryptText); 
            CryptoStream CStream=new CryptoStream(MStream,myCryptoTrans,CryptoStreamMode.Read); 
            decryptText=new byte[encryptText.Length]; 
            CStream.Read(decryptText,0,decryptText.Length); 
            //StringBuilder EnText=new StringBuilder(); 
            CStream.Close(); 
            return Encoding.UTF8.GetString(decryptText); 
        } 
        #endregion

        #region DESEncrypt
        public static string DESEncrypt(string CryptText, string CryptKey,string CryptIV) 
        { 
            DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 
            byte[] textOut = Encoding.UTF8.GetBytes(CryptText); 
            byte[] DESKey=ASCIIEncoding.UTF8.GetBytes( (CryptKey + m_key).Substring(0,8) ); 
            byte[] DESIV=ASCIIEncoding.UTF8.GetBytes( (CryptIV + m_iv).Substring(0,8) ); 
            MemoryStream MStream = new MemoryStream(); 
            CryptoStream CStream = new CryptoStream(MStream, des.CreateEncryptor(DESKey,DESIV),CryptoStreamMode.Write); 
            CStream.Write(textOut, 0, textOut.Length); 
            CStream.FlushFinalBlock(); 
            StringBuilder StrRes = new StringBuilder(); 
            foreach(byte Byte in MStream.ToArray()) 
            { 
                StrRes.AppendFormat("{0:x2}", Byte); 
            } 
            return StrRes.ToString(); 
        } 
        #endregion

        #region DESDecrypt
        public static string DESDecrypt(string CryptText, string CryptKey,string CryptIV) 
        { 
            DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 
            byte[] textOut = new byte[CryptText.Length / 2]; 
            for(int Count = 0; Count < CryptText.Length; Count+=2) 
            { 
                textOut[Count/2] = (byte)(Convert.ToInt32(CryptText.Substring(Count , 2), 16)); 
            } 
            byte[] DESKey=ASCIIEncoding.UTF8.GetBytes( (CryptKey + m_key).Substring(0,8) ); 
            byte[] DESIV=ASCIIEncoding.UTF8.GetBytes( (CryptIV + m_iv).Substring(0,8) ); 
            MemoryStream MStream = new MemoryStream(); 
            CryptoStream CStream = new CryptoStream(MStream, des.CreateDecryptor(DESKey,DESIV),CryptoStreamMode.Write); 
            CStream.Write(textOut, 0, textOut.Length); 
            CStream.FlushFinalBlock(); 
            return System.Text.Encoding.UTF8.GetString(MStream.ToArray()); 
        } 
        #endregion
        public static string SHA1Encrypt(string EncryptText) 
        { 
            byte[] StrRes=Encoding.Default.GetBytes(EncryptText); 
            HashAlgorithm mySHA=new SHA1CryptoServiceProvider(); 
            StrRes=mySHA.ComputeHash(StrRes); 
            StringBuilder EnText=new StringBuilder(); 
            foreach(byte Byte in StrRes) 
            { 
                EnText.AppendFormat("{0:x2}",Byte); 
            } 
            return EnText.ToString(); 
        } 
        public static string HMACSHA1Encrypt(string EncryptText,string EncryptKey) 
        { 
            byte[] StrRes=Encoding.UTF8.GetBytes(EncryptText); 
            HMACSHA1 myHMACSHA1=new HMACSHA1(Encoding.UTF8.GetBytes( EncryptKey )); 

            CryptoStream CStream = new CryptoStream( Stream.Null , myHMACSHA1 , CryptoStreamMode.Write ); 
            CStream.Write( StrRes,0,StrRes.Length ); 
            CStream.Close();
            StringBuilder EnText=new StringBuilder(); 

            foreach(byte Byte in myHMACSHA1.Hash) 
            { 
                EnText.AppendFormat("{0:x2}",Byte); 
            } 
            return EnText.ToString(); 
        } 
        public static string MD5Encrypt(string CryptText) 
        { 
            MD5 myMD5=new MD5CryptoServiceProvider(); 
            byte[] HashCode; 
            HashCode=Encoding.Default.GetBytes(CryptText); 
            HashCode=myMD5.ComputeHash(HashCode); 
            StringBuilder EnText=new StringBuilder(); 
            foreach(byte Byte in HashCode) 
            { 
                EnText.AppendFormat("{0:x2}",Byte); 
            } 
            return EnText.ToString(); 
        } 
    }
}

DES编码解码器