NTAG212 Mifare Ultralight 带身份验证

我是 NFC Android 新手，我已经被困了好几天试图获取第 4 页到第 7 页NTAG212 Mifare Ultralight 带身份验证，我已经有了 PWD 和 PACK 来做PWD_AUTH基于NTAG212 Docs.

我采用这种方法...

//assume password as array of bytes
//assume pack as array of bytes
try{
nfc.connect();
byte[] cmd1 = nfc.transceive(new byte[]{ (byte) 0x30, (byte) 0x00 }); //read the page 0     to make the NFC active
nfc.transceive(new byte[]{
   (byte) 0x1B, //command for PWD_AUTH
   pass[0],
   pass[1],
   pass[2],
   pass[3]
});
byte[] cmd4 = nfc.transceive(new byte[]{ (byte) 0x30, (byte) 0x04 }); //read the page 4
}catch(TagLostException e){
  e.printStackTrace();
}catch(IOException e){
  e.printStachTrace();
}finally{
    try{
        nfc.close();
    }catch(Exception e){
      //display failed to close
    }
}

我总是收到android.nfc.TagLostException: Tag was lost.向 NFC 发送 PWD_AUTH 命令后出错。有人可以告诉我我做错了什么吗？我的做法正确吗？请帮忙。

注意：我已经多次阅读 NTAG212 的文档，搜索了 google、stackoverflow 和所有可能的资源。

TIA,
Kenster

您发送到标签的 PWD_AUTH 命令没有多大意义。

PWD_AUTH 命令的想法是，您发送密码（4 字节值），如果您使用正确的密码进行身份验证，标签将以其密码确认 (PACK) 值（2 字节值）进行响应。然后，您可以根据预期的密码确认验证 PACK 值，以“验证”标签。

所以正确的命令是：

byte[] response = nfc.transceive(new byte[] {
    (byte) 0x1B, // PWD_AUTH
    pass[0], pass[1], pass[2], pass[3]
});
if ((response != null) && (response.length >= 2)) {
   byte[] pack = Arrays.copyOf(response, 2);
   // TODO: verify PACK to confirm that tag is authentic (not really,
   // but that whole PWD_AUTH/PACK authentication mechanism was not
   // really meant to bring much security, I hope; same with the
   // NTAG signature btw.)
}

启用密码保护所需的条件（在 NTAG212 上）：

1. 将 PWD（第 39 页）设置为您想要的密码（默认值为0xFFFFFFFF).

   byte[] response = nfc.transceive(new byte[] {
       (byte) 0xA2, // WRITE
       (byte) 39,   // page address
       pass[0], pass[1], pass[2], pass[3]
   });
   

2. 将 PACK（第 40 页，字节 0-1）设置为您所需的密码确认（默认值为0x0000).

   byte[] response = nfc.transceive(new byte[] {
       (byte) 0xA2, // WRITE
       (byte) 40,   // page address
       pack[0], pack[1],   // bytes 0-1 are PACK value
       (byte) 0, (byte) 0  // other bytes are RFU and must be written as 0
   });
   

3. 将 AUTHLIM（第 38 页，字节 0，位 2-0）设置为密码验证尝试失败的最大次数（将此值设置为 0 将允许无限次数的 PWD_AUTH 尝试）。

4. 将 PROT（第 38 页，字节 0，位 7）设置为所需值（0 = 仅写访问需要 PWD_AUTH，1 = 读和写访问需要 PWD_AUTH）。

   byte[] response = nfc.transceive(new byte[] {
       (byte) 0x30, // READ
       (byte) 38    // page address
   });
   if ((response != null) && (response.length >= 16)) {  // read always returns 4 pages
       boolean prot = false;  // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
       int authlim = 0; // value between 0 and 7
       response = nfc.transceive(new byte[] {
           (byte) 0xA2, // WRITE
           (byte) 38,   // page address
           (byte) ((response[0] & 0x078) | (prot ? 0x080 : 0x000) | (authlim & 0x007)),
           response[1], response[2], response[3]  // keep old value for bytes 1-3, you could also simply set them to 0 as they are currently RFU and must always be written as 0 (response[1], response[2], response[3] will contain 0 too as they contain the read RFU value)
       });
   }
   

5. 将 AUTH0（第 37 页，字节 3）设置为需要密码验证的第一页。

   byte[] response = nfc.transceive(new byte[] {
       (byte) 0x30, // READ
       (byte) 37    // page address
   });
   if ((response != null) && (response.length >= 16)) {  // read always returns 4 pages
       boolean prot = false;  // false = PWD_AUTH for write only, true = PWD_AUTH for read and write
       int auth0 = 0; // first page to be protected, set to a value between 0 and 37 for NTAG212
       response = nfc.transceive(new byte[] {
           (byte) 0xA2, // WRITE
           (byte) 37,   // page address
           response[0], // keep old value for byte 0
           response[1], // keep old value for byte 1
           response[2], // keep old value for byte 2
           (byte) (auth0 & 0x0ff)
       });
   }
   

如果你使用MifareUltralight标签技术，而不是使用transceive直接使用方法，也可以使用readPages and writePage方法：

• 读命令

  byte[] response = nfc.transceive(new byte[] {
      (byte) 0x30,                  // READ
      (byte) (pageAddress & 0x0ff)  // page address
  });
  

  相当于

  byte[] response = nfc.readPages(pageAddress);
  

• 写命令

  byte[] data = { (byte)..., (byte)..., (byte)..., (byte)... };
  byte[] response = nfc.transceive(new byte[] {
      (byte) 0xA2,                  // WRITE
      (byte) (pageAddress & 0x0ff), // page address
      data[0], data[1], data[2], data[3]
  });
  

  相当于

  nfc.writePage(pageAddress, data);