加密解密（Base64、AES、MD5、HMACSHA256）

/// <summary>
        /// Base64加密
        /// </summary>
        /// <param name="source">待加密的明文</param>
        /// <param name="encode">编码方式</param>
        /// <returns></returns>
        public static string EncodeBase64(string source, Encoding encode)
        {
            byte[] bytes = encode.GetBytes(source);
            return Convert.ToBase64String(bytes);
        }

        /// <summary>
        /// Base64加密
        /// </summary>
        /// <param name="source">待加密的明文</param>
        /// <returns></returns>
        /// 
        /// <seealso cref="SecurityUtil.EncodeBase64(string,Encoding)">  
        /// 参看SecurityUtil.EncodeBase64(string,Encoding)方法的说明 </seealso>  
        public static string EncodeBase64(string source)
        {
            return EncodeBase64(source, Encoding.UTF8);
        }

        /// <summary>
        /// Base64解密
        /// </summary>
        /// <param name="source">待解密的明文</param>
        /// <param name="encode">编码方式</param>
        /// <returns></returns>
        public static string DecodeBase64(string source, Encoding encode)
        {
            string decode = "";
            byte[] bytes = Convert.FromBase64String(source);
            decode = encode.GetString(bytes);
            return decode;
        }

        /// <summary>
        /// AES加密 
        /// </summary>
        /// <param name="context">待加密的内容</param>
        /// <param name="keyBytes">加密密钥</param>
        /// <param