C# 图片防篡改

1.逻辑：在读取图片文件流后，添加自己的加密签名信息，然后再保存文件，读取时截取对应的字节长度，以相同的方式转换成字符串并对比，确认图片是否更改

2. 加密方法

         /// <summary>
        /// MD5:  加密方式
        /// </summary>
        public static string MD5Hash(string input)
        {
            using (var md5 = MD5.Create())
            {
                var result = md5.ComputeHash(Encoding.ASCII.GetBytes(input));
                var strResult = BitConverter.ToString(result);
                return strResult.Replace("-", "");
            }
        }    

　3.添加自定义签名信息　

/// <summary>
        /// 图片加密签名
        /// </summary>
        public static void ImageAddMD5Hash()
        {
            var str = "QWERTYUIOP"; // 签名
            var md5ste = MD5Hash(str);
            string path = $"{AppDomain.CurrentDomain.BaseDirectory}";
            string url = $"{path}File/Page4.png";  // 图片文件
            MemoryStream stream1 = new MemoryStream();
            using (FileStream stream = new FileStream(url, FileMode.Open, FileAccess.Read,FileShare.Read))
            {
                var dd = Encoding.Unicode.GetBytes(md5ste);
                //byte[] strbytes = new byte[dd.Length];
                byte[] bytes = new byte[stream.Length+dd.Length];
                stream.Read(bytes, 0, (int)stream.Length);
                Array.Copy(dd,0, bytes, stream.Length, 64);
                Console.WriteLine(stream1.Length);
                FileStream fs = new FileStream($"{path}File/Page6.png", FileMode.Create);  // 加密后的图片
                fs.Write(bytes, 0, bytes.Length);
                fs.Dispose();
            }             
            
        } 

　　4. 获取图片加密信息

/// <summary>
        /// 图片获得加密签名信息
        /// </summary>
        public static void ImageGetMD5Hash()
        {
            string path = $"{AppDomain.CurrentDomain.BaseDirectory}";
            string url = $"{path}File/Page4.png";  // 图片文件
            var stream = File.OpenRead(url);
            MemoryStream memoryStream = new MemoryStream();
            byte[] bytes = new byte[stream.Length];
            stream.Read(bytes, 0, bytes.Length);

            //byte[] bytes = new byte[16];

            byte[] strbytes = new byte[64];
            Array.Copy(bytes, bytes.Length - 64, strbytes, 0, 64);
            var str = Encoding.Unicode.GetString(strbytes);  // 加密的信息
            Console.WriteLine(str);
            stream.Dispose();
        }