这个C#类是一个基于Base64的加密和解密类，用户可以可以使用默认的秘钥进行加密、解密，也可以自己设定秘钥进行加密和解密，非常实用

using System;
using System.Security.Cryptography; 
using System.Text;
namespace DotNet.Utilities
{
    /// <summary>
    /// Encrypt 的摘要说明。
    /// </summary>
    public class DEncrypt
    {
        /// <summary>
        /// 构造方法
        /// </summary>
        public DEncrypt() 
        { 
        }
 
        #region 使用 缺省密钥字符串 加密/解密string
 
        /// <summary>
        /// 使用缺省密钥字符串加密string
        /// </summary>
        /// <param name="original">明文</param>
        /// <returns>密文</returns>
        public static string Encrypt(string original)
        {
            return Encrypt(original,"sharejs.com");
        }
        /// <summary>
        /// 使用缺省密钥字符串解密string
        /// </summary>
        /// <param name="original">密文</param>
        /// <returns>明文</returns>
        public static string Decrypt(string original)
        {
            return Decrypt(original,"sharejs.com",System.Text.Encoding.Default);
        }
 
        #endregion
 
        #region 使用 给定密钥字符串 加密/解密string
        /// <summary>
        /// 使用给定密钥字符串加密string
        /// </summary>
        /// <param name="original">原始文字</param>
        /// <param name="key">密钥</param>
        /// <param name="encoding">字符编码方案</param>
        /// <returns>密文</returns>
        public static string Encrypt(string original, string key) 
        { 
            byte[] buff = System.Text.Encoding.Default.GetBytes(original); 
            byte[] kb = System.Text.Encoding.Default.GetBytes(key);
            return Convert.ToBase64String(Encrypt(buff,kb));     
        }
        /// <summary>
        /// 使用给定密钥字符串解密string
        /// </summary>
        /// <param name="original">密文</param>
        /// <param name="key">密钥</param>
        /// <returns>明文</returns>
        public static string Decrypt(string original, string key)
        {
            return Decrypt(original,key,System.Text.Encoding.Default);
        }
 
        /// <summary>
        /// 使用给定密钥字符串解密string,返回指定编码方式明文
        /// </summary>
        /// <param name="encrypted">密文</param>
        /// <param name="key">密钥</param>
        /// <param name="encoding">字符编码方案</param>
        /// <returns>明文</returns>
        public static string Decrypt(string encrypted, string key,Encoding encoding) 
        {      
            byte[] buff = Convert.FromBase64String(encrypted); 
            byte[] kb = System.Text.Encoding.Default.GetBytes(key);
            return encoding.GetString(Decrypt(buff,kb));     
        } 
        #endregion
 
        #region 使用 缺省密钥字符串 加密/解密/byte[]
        /// <summary>
        /// 使用缺省密钥字符串解密byte[]
        /// </summary>
        /// <param name="encrypted">密文</param>
        /// <param name="key">密钥</param>
        /// <returns>明文</returns>
        public static byte[] Decrypt(byte[] encrypted) 
        { 
            byte[] key = System.Text.Encoding.Default.GetBytes("sharejs.com");
            return Decrypt(encrypted,key);    
        }
        /// <summary>
        /// 使用缺省密钥字符串加密
        /// </summary>
        /// <param name="original">原始数据</param>
        /// <param name="key">密钥</param>
        /// <returns>密文</returns>
        public static byte[] Encrypt(byte[] original) 
        { 
            byte[] key = System.Text.Encoding.Default.GetBytes("sharejs.com");
            return Encrypt(original,key);    
        } 
        #endregion
 
        #region  使用 给定密钥 加密/解密/byte[]
 
        /// <summary>
        /// 生成MD5摘要
        /// </summary>
        /// <param name="original">数据源</param>
        /// <returns>摘要</returns>
        public static byte[] MakeMD5(byte[] original)
        {
            MD5CryptoServiceProvider hashmd5 = new MD5CryptoServiceProvider();  
            byte[] keyhash = hashmd5.ComputeHash(original);      
            hashmd5 = null; 
            return keyhash;
        }
 
 
        /// <summary>
        /// 使用给定密钥加密
        /// </summary>
        /// <param name="original">明文</param>
        /// <param name="key">密钥</param>
        /// <returns>密文</returns>
        public static byte[] Encrypt(byte[] original, byte[] key) 
        { 
            TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider();      
            des.Key =  MakeMD5(key);
            des.Mode = CipherMode.ECB; 
      
            return des.CreateEncryptor().TransformFinalBlock(original, 0, original.Length);    
        } 
 
        /// <summary>
        /// 使用给定密钥解密数据
        /// </summary>
        /// <param name="encrypted">密文</param>
        /// <param name="key">密钥</param>
        /// <returns>明文</returns>
        public static byte[] Decrypt(byte[] encrypted, byte[] key) 
        { 
            TripleDESCryptoServiceProvider des = new TripleDESCryptoServiceProvider(); 
            des.Key =  MakeMD5(key);   
            des.Mode = CipherMode.ECB; 
 
            return des.CreateDecryptor().TransformFinalBlock(encrypted, 0, encrypted.Length);
        } 
   
        #endregion
 
         
 
         
    }
}