移动支付之Android(安卓)HCE的基本使用
本文来自http://blog.csdn.net/hellogv/ ,引用必须注明出处!
最近NFC支付挺火的,趁国庆宅在家,学习下Android 卡模拟(Host-based Card Emulation)。HCE的特点是模拟智能IC卡(ISO 7816-4),可用于金融和行业应用,相应地,CardReader例子中使用IsoDep。
智能IC卡本身是一个微型计算机,常见为Java Card平台,特别是多功能集于一身的卡(如联名卡),Java Card比J2ME更加硬件受限。Java Card可以运行一到多个Java Applet,这些Applet也就是卡应用,例如一张能刷公交的银行卡可能就包含了2个Applet。每个Applet都有一个AID,受理终端(刷卡设备)通过AID来找到对应的卡应用(受理终端向卡发送SELECT命令),受理终端找到对应的卡应用后就可以进行数据交互,交互的数据一般是密文,不联机解密的话,用对称算法,联机解密的话,用非对称和对称算法都行。
HCE是软件模拟的智能IC卡,所以也会有AID。本文CardEmulation只注册一个AID。本文的代码改自Android 4.4 Sample,没改动CardEmulation,简化CardReader并支持Android 2.3系统,适应低版本的NFC手机做虚拟卡的卡读取了。使用努比亚Z7 MAX做CardEmulation,小米 2A作CardReader。本文的代码可以到http://pan.baidu.com/s/1o6JnXr0下载。个人觉得阅读CardReader核心代码更能了解2者交互的过程:
public final class CardReader { private static final String TAG = "LoyaltyCardReader"; // AID for our loyalty card service. private static final String SAMPLE_LOYALTY_CARD_AID = "F222222222"; // ISO-DEP command HEADER for selecting an AID. // Format: [Class | Instruction | Parameter 1 | Parameter 2] private static final String SELECT_APDU_HEADER = "00A40400"; // "OK" status word sent in response to SELECT AID command (0x9000) private static final byte[] SELECT_OK_SW = {(byte) 0x90, (byte) 0x00};public static String[][] TECHLISTS;public static IntentFilter[] FILTERS;static {try {//the tech lists used to perform matching for dispatching of the ACTION_TECH_DISCOVERED intentTECHLISTS = new String[][] { { IsoDep.class.getName() },{ NfcV.class.getName() }, { NfcF.class.getName() }, };FILTERS = new IntentFilter[] { new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED, "*/*") };} catch (Exception e) {}} static public String tagDiscovered(Tag tag) {Log.i(TAG, "New tag discovered");// Android's Host-based Card Emulation (HCE) feature implements the// ISO-DEP (ISO 14443-4)// protocol.//// In order to communicate with a device using HCE, the discovered tag// should be processed// using the IsoDep class.IsoDep isoDep = IsoDep.get(tag);if (isoDep != null) {try {// Connect to the remote NFC deviceisoDep.connect();// Build SELECT AID command for our loyalty card service.// This command tells the remote device which service we wish to// communicate with.Log.i(TAG, "Requesting remote AID: " + SAMPLE_LOYALTY_CARD_AID);byte[] command = BuildSelectApdu(SAMPLE_LOYALTY_CARD_AID);// Send command to remote deviceLog.i(TAG, "Sending: " + ByteArrayToHexString(command));byte[] result = isoDep.transceive(command);// If AID is successfully selected, 0x9000 is returned as the// status word (last 2// bytes of the result) by convention. Everything before the// status word is// optional payload, which is used here to hold the account// number.int resultLength = result.length;byte[] statusWord = { result[resultLength - 2],result[resultLength - 1] };byte[] payload = Arrays.copyOf(result, resultLength - 2);if (Arrays.equals(SELECT_OK_SW, statusWord)) {// The remote NFC device will immediately respond with its// stored account numberString accountNumber = new String(payload, "UTF-8");Log.i(TAG, "Received: " + accountNumber);// Inform CardReaderFragment of received account numberreturn accountNumber;}} catch (IOException e) {Log.e(TAG, "Error communicating with card: " + e.toString());}}return null;}public static String load(Parcelable parcelable) {// 从Parcelable筛选出各类NFC标准数据final Tag tag = (Tag) parcelable;return tagDiscovered(tag);} /** * Build APDU for SELECT AID command. This command indicates which service a reader is * interested in communicating with. See ISO 7816-4. * * @param aid Application ID (AID) to select * @return APDU for SELECT AID command */ public static byte[] BuildSelectApdu(String aid) { // Format: [CLASS | INSTRUCTION | PARAMETER 1 | PARAMETER 2 | LENGTH | DATA] return HexStringToByteArray(SELECT_APDU_HEADER + String.format("%02X", aid.length() / 2) + aid); } /** * Utility class to convert a byte array to a hexadecimal string. * * @param bytes Bytes to convert * @return String, containing hexadecimal representation. */ public static String ByteArrayToHexString(byte[] bytes) { final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'}; char[] hexChars = new char[bytes.length * 2]; int v; for ( int j = 0; j < bytes.length; j++ ) { v = bytes[j] & 0xFF; hexChars[j * 2] = hexArray[v >>> 4]; hexChars[j * 2 + 1] = hexArray[v & 0x0F]; } return new String(hexChars); } /** * Utility class to convert a hexadecimal string to a byte string. * * <p>Behavior with input strings containing non-hexadecimal characters is undefined. * * @param s String containing hexadecimal characters to convert * @return Byte array generated from input */ public static byte[] HexStringToByteArray(String s) { int len = s.length(); byte[] data = new byte[len / 2]; for (int i = 0; i < len; i += 2) { data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16)); } return data; }
简单地说:
1。CardReader使用SAMPLE_LOYALTY_CARD_AID +SELECT_APDU_HEADER 生成 SELECT APDU;
2。CardReader发送SELECT APDU到CardEmulation后,CardEmulation返回SELECT_OK_SW + accountNumber。
其中SAMPLE_LOYALTY_CARD_AID ,SELECT_APDU_HEADER ,SELECT_OK_SW 都必须是CardReader与CardEmulation双方定义好的。另外,CardReader在4.4和4.4以下系统的用法也略有不同,4.4以下系统用onNewIntent(),4.4系统就要通过enableReaderMode()方法,如果4.4系统用onNewIntent()的话,会导致一直P2P,而不是卡与读卡器的关系。
public final class NFCard extends Activity {private NfcAdapter nfcAdapter;private PendingIntent pendingIntent;private EditText board;private int sysVersion;@Overridepublic void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.cardreader);board = (EditText) this.findViewById(R.id.editText1);nfcAdapter = NfcAdapter.getDefaultAdapter(this);pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this,getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);//区分系统版本sysVersion = Integer.parseInt(VERSION.SDK);if(sysVersion<19)onNewIntent(getIntent());}@Overrideprotected void onPause() {super.onPause();if (nfcAdapter != null){nfcAdapter.disableForegroundDispatch(this);disableReaderMode();}}@Overrideprotected void onResume() {super.onResume();if (nfcAdapter != null){nfcAdapter.enableForegroundDispatch(this, pendingIntent,CardReader.FILTERS, CardReader.TECHLISTS);enableReaderMode();}Log.e("NFC----", IsoDep.class.getName());refreshStatus();}@Overrideprotected void onNewIntent(Intent intent) {super.onNewIntent(intent);final Parcelable p = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);Log.d("NFCTAG", intent.getAction());board.setText((p != null) ? CardReader.load(p) : null);} @TargetApi(19) private void enableReaderMode() { if(sysVersion<19) return; int READER_FLAGS = NfcAdapter.FLAG_READER_NFC_A | NfcAdapter.FLAG_READER_SKIP_NDEF_CHECK; if (nfcAdapter != null) { nfcAdapter.enableReaderMode(this, new MyReaderCallback(), READER_FLAGS, null); } } @TargetApi(19) private void disableReaderMode() { if(sysVersion<19) return; if (nfcAdapter != null) { nfcAdapter.disableReaderMode(this); } } @TargetApi(19) public class MyReaderCallback implements NfcAdapter.ReaderCallback {@Overridepublic void onTagDiscovered(final Tag arg0) {NFCard.this.runOnUiThread(new Runnable() { @Override public void run() { board.setText(CardReader.tagDiscovered(arg0)); } });}} protected void onActivityResult(int requestCode, int resultCode, Intent data) {refreshStatus();}private void refreshStatus() {final String tip;if (nfcAdapter == null)tip = this.getResources().getString(R.string.tip_nfc_notfound);else if (nfcAdapter.isEnabled())tip = this.getResources().getString(R.string.tip_nfc_enabled);elsetip = this.getResources().getString(R.string.tip_nfc_disabled);final StringBuilder s = new StringBuilder(this.getResources().getString(R.string.app_name));s.append(" -- ").append(tip);setTitle(s);}
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