使用Android NFC将超过261个字节发送到Java卡 [英] Send more than 261 bytes to Java Card with Android NFC

问题描述

我想通过NFC（类 IsoDep ）将长度为1699字节的APDU发送到Java卡智能卡。我收到错误消息

I want to send an APDU with a length of 1699 bytes via NFC (class IsoDep) to a Java Card smartcard. I get the error

java.io.IOException：收发长度超出了支持的最大值

java.io.IOException: Transceive length exceeds supported maximum

我的手机是三星Galaxy S7。

My phone is a Samsung Galaxy S7.

我在卡上的applet中使用了扩展长度。我已验证该卡支持扩展长度。我通过向卡发送一个4000字节的APDU通过pyapdutool对此进行了测试。

I use extended-length in my applet on the card. I have verified that the card supports extended length. I tested this via pyapdutool by sending an APDU with 4000 bytes to the card.

我发现在编写此代码时，结果为 false ：

I found that when I write this code, the result is false:

final Tag t = (Tag) tag;
myTag = IsoDep.get(t);
boolean result = myTag.isExtendedLengthApduSupported();

我的清单中有此内容：

<activity
        android:name=".test"
        android:label="@string/title_test"
        android:launchMode="singleTop"
        android:theme="@style/AppTheme.NoActionBar" >
    <action android:name="android.nfc.action.TAG_DISCOVERED" />
    <category android:name="android.intent.category.DEFAULT" />
    <intent-filter>
        <action android:name="android.nfc.action.NDEF_DISCOVERED" />
    </intent-filter>
</activity>

如何通过Android NFC发送1699字节（或任何长度大于261字节的长度）的APDU

How can I send an APDU with 1699 bytes (or any length greater than 261 bytes) through Android NFC?

推荐答案

简短答案：您不能轻易做到这一点。

Short answer: You can't easily do that.

您已经发现 IsoDep 不支持设备上的扩展长度APDU（即 isoDep.isExtendedLengthApduSupported（）返回 false ）。实际上，这不是并不意味着您不能通过 IsoDep 对象发送扩展长度的APDU。实际上，这仅意味着 IsoDep 对象不会将扩展长度的APDU正确地分割为两个以上的ISO-DEP块，因此，长度超过261个字节的APDU将被假定超过了发送缓冲区的大小。您仍然应该能够发送长度小于< = 261字节的扩展长度APDU。

You already found out that IsoDep does not "support" extended-length APDUs on your device (i.e. isoDep.isExtendedLengthApduSupported() returns false). In fact this does not mean that you can't send extended-length APDUs through the IsoDep object. It actually only means that the IsoDep object won't properly split extended-length APDUs across more than two ISO-DEP blocks and consequently an APDU that is longer than 261 bytes will be assumed to exceed the transmit buffer size. You should still be able to send extended-length APDUs with sizes <= 261 bytes.

所以 isoDep.isExtendedLengthApduSupported（）实际上指示您是否可以在一个ISO-DEP收发中发送超过261个字节。

So isoDep.isExtendedLengthApduSupported() actually indicates if you can send more than 261 bytes in one ISO-DEP transceive.

您可以采取的克服此问题的措施是不使用 IsoDep 对象，而是在 NfcA 对象（如果您的卡基于NFC-A / ISO / IEC 14443 Type A）或 NfcB 对象（如果您的卡基于NFC-B / ISO / IEC 14443 B型和（如果您的设备支持通过 NfcB 对象交换数据）。然后，您可以将扩展长度的APDU拆分为对于NFC控制器的收发缓冲区足够小的ISO-DEP块（通常为253个字节，包括标头字节，不包括CRC字节）。但是，自己处理ISO-DEP协议还意味着您必须注意正确的ISO-DEP激活，处理块编号，块确认，超时，等待时间扩展等。这相当复杂，尤其是超时由于Android NFC堆栈存在延迟，因此不容易观察。

What you could do to overcome this problem is to not use the IsoDep object at all and, instead, manually implement ISO-DEP (the ISO/IEC 14443-4 transmission protocol) on top of the NfcA object (if your card is based on NFC-A / ISO/IEC 14443 Type A) or the NfcB object (if your card is based on NFC-B / ISO/IEC 14443 Type B and if your device supports exchanging data over the NfcB object). You could then split your extended-length APDUs into ISO-DEP blocks that are small enough for the transceive buffer of the NFC controller (typically 253 bytes including the header bytes, excluding the CRC bytes). However, handling the ISO-DEP protocol yourself also means that you have to take care of proper ISO-DEP activation, of handling block numbering, block acknowledgements, timeouts, waiting-time extension, etc. Which is rather complicated, and particularly timeouts are not easy to observe due to the delays through the Android NFC stack.

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