加密解密

　　　/// <summary>
        /// 带有密钥的加解密
        /// 加密
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public static string KeyEncrypt(string str,string key)
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
            provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
            byte[] bytes = Encoding.GetEncoding("GB2312").GetBytes(str);
            MemoryStream stream = new MemoryStream();
            CryptoStream stream2 = new CryptoStream(stream, provider.CreateEncryptor(), CryptoStreamMode.Write);
            stream2.Write(bytes, 0, bytes.Length);
            stream2.FlushFinalBlock();
            StringBuilder builder = new StringBuilder();
            foreach (byte num in stream.ToArray())
            {
                builder.AppendFormat("{0:X2}", num);
            }
            stream.Close();
            return builder.ToString();
        }

　　   /// <summary>
        /// 带有密钥的加解密
        /// 解密
        /// </summary>
        /// <param name="data"></param>
        /// <returns></returns>
        public static string KeyDecrypt(string str,string key)
        {
            try
            {
                DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
                provider.Key = Encoding.ASCII.GetBytes(key.Substring(0, 8));
                provider.IV = Encoding.ASCII.GetBytes(key.Substring(0, 8));
                byte[] buffer = new byte[str.Length / 2];
                for (int i = 0; i < (str.Length / 2); i++)
                {
                    int num2 = Convert.ToInt32(str.Substring(i * 2, 2), 0x10);
                    buffer[i] = (byte)num2;
                }
                MemoryStream stream = new MemoryStream();
                CryptoStream stream2 = new CryptoStream(stream, provider.CreateDecryptor(), CryptoStreamMode.Write);
                stream2.Write(buffer, 0, buffer.Length);
                stream2.FlushFinalBlock();
                stream.Close();
                return Encoding.GetEncoding("GB2312").GetString(stream.ToArray());
            }
            catch
            {
                return "";
            }
        }