如何使用 Xamarin 密码保护 NFC NTAG215 标签

Question

作为我的项目要求的一部分，我想用密码保护我的 NFC 标签以防止覆盖。我在互联网上进行了很多搜索，但找不到任何可靠的指南或在 Xamarin 中解释的文章。所以如果有人使用Xamarin做过NFC标签的密码保护，请指导我。

Answer 1

您可以在 Xamarin.Android 中使用以下步骤在 NFC NTAG215 标签中添加密码保护

1. 根据 Plugin.NFC 文档将更改添加到您的代码。
2. 将以下方法添加到您的 MainActivity.cs 类中，以检查、添加和删除标签的密码配置。

public  class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity, NFCTagConfiguration
    {
        public Tag maintag;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            CrossCurrentActivity.Current.Init(this, savedInstanceState);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            CrossNFC.Init(this);
            global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
            base.OnCreate(savedInstanceState);
            LoadApplication(new App());
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);
            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }
        protected override void OnResume()
        {
            base.OnResume();
            // Plugin NFC: Restart NFC listening on resume (needed for Android 10+) 
            CrossNFC.OnResume();
        }

        protected override async void OnNewIntent(Intent intent)
        {
            base.OnNewIntent(intent);
            maintag = (Tag)intent.GetParcelableExtra(NfcAdapter.ExtraTag);
            // Plugin NFC: Tag Discovery Interception
            CrossNFC.OnNewIntent(intent);
            if (maintag != null)
            {
                ////Handle your logic here
                //1.Check password configuration
                //2.Add password protection
                //3.Remove password protection
            }
        }
        public bool CheckConfiguration()
        {
            bool passExist;
            try
            {
                MifareUltralight mu = MifareUltralight.Get(maintag);
                mu.Connect();
                var answer = mu.ReadPages(131);
                byte auth0 = answer[3];
                passExist = auth0 < (byte)0xEB;
                mu.Close();
            }
            catch (Exception e)
            {
                // mu.Close();
                passExist = true;
            }
            return passExist;
        }
         public bool AddConfiguration(string PSWD)
        {
            NfcA nfcaTag = NfcA.Get(maintag);
            bool IsConfigured;
            try
            {
                byte[] SET_PACK_VALUE = { (byte)0xA2, (byte)0x86, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00 };
                byte[] PWD = Encoding.ASCII.GetBytes("1234");
                byte[] SET_PASSWORD = { (byte)0xA2, (byte)0x85, PWD[0], PWD[1], PWD[2], PWD[3] };
                byte[] SET_AUTH0_VALUE = { (byte)0xA2, (byte)0x83, (byte)0x04, (byte)0x00, (byte)0x00, (byte)0x04 };
                string pack = Encoding.ASCII.GetString(SET_PASSWORD);
                nfcaTag.Connect();
                nfcaTag.Transceive(SET_PACK_VALUE);
                nfcaTag.Transceive(SET_PASSWORD);
                nfcaTag.Transceive(SET_AUTH0_VALUE);
                nfcaTag.Close();
                IsConfigured = true;
            }
            catch (Exception ex)
            {
                nfcaTag.Close();
                IsConfigured = false;
            }
            return IsConfigured;
        }
        public bool RemoveConfiguration(string PSWD)
        {
            byte[] RESET_PACK_VALUE = { (byte)0xA2, (byte)0x86, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0x00 };
            byte[] RESET_AUTH0_VALUE = { (byte)0xA2, (byte)0x83, (byte)0x00, (byte)0x00, (byte)0x00, (byte)0xFF };
            byte[] PWD = Encoding.ASCII.GetBytes("1234");
            byte[] SET_PASSWORD = { (byte)0x1b, PWD[0], PWD[1], PWD[2], PWD[3] };
            MifareUltralight mfu = MifareUltralight.Get(maintag);
            bool IsConfigured;
            try
            {
                byte[] answer;
                mfu.Connect();
                answer = mfu.Transceive(SET_PASSWORD);  
                mfu.Transceive(RESET_AUTH0_VALUE);
                mfu.Transceive(RESET_PACK_VALUE);
                mfu.Close();
                IsConfigured = true;
            }
            catch (Exception e)
            {
                mfu.Close();
                IsConfigured = false;
            }
            return IsConfigured;
        }
        }

如果您使用其他标签，您可以参考NTAG 213/215/216数据表了解APDU命令。