我是 NFC Android 的新手,几天来我一直在尝试获取 NTAG212 Mifare Ultralight with Authentication 的第 4 页到第 7 页,我已经有了 PWD 和 PACK 来执行 < strong>PWD_AUTH 基于 NTAG212 文档。
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?我的方法正确吗?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,
肯斯特
最佳答案
您发送给标签的 PWD_AUTH 命令没有多大意义。
PWD_AUTH 命令的想法是您发送密码(一个 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(一个 2 字节值)进行响应。然后,您可以根据预期的密码确认 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):
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] });
将 PACK(第 40 页,字节 0-1)设置为您想要的密码确认(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 });
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 PWD_AUTH 尝试)。
将 PROT(第 38 页,字节 0,位 7)设置为您想要的值(0 = PWD_AUTH 仅用于写入访问,1 = PWD_AUTH 是读取和写入访问所必需的)。
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) }); }
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) }); }
如果使用MifareUltralight
标签技术,除了直接使用transceive
方法,还可以使用readPages
和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);
关于java - 带身份验证的 NTAG212 Mifare Ultralight,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22719465/