這是我們為大家提供的一篇關於移動支付之Android HCE的使用方法的文章,接下來就讓我們一起來了解一下吧!
最近NFC支付挺火的,趁國慶宅在家,學習下Android 卡模擬(Host-based Card Emulation)。HCE的特點是模擬智能IC卡(ISO 7816-4),可用於金融和行業應用,相應地,CardReader例子中使用IsoDep。
智能IC卡本身是一個微型計算機,常見為Java Card平台,特別是多功能集於一身的卡(如聯名卡),Java Card比J2ME更加硬件受限。Java Card可以運行一到多個Java Applet,這些Applet也就是卡應用,例如一張能刷公交的銀行卡可能就包含了2個Applet。每個Applet都有一個AID,受理終端(刷卡設備)通過AID來找到對應的卡應用(受理終端向卡發送SELECT命令),受理終端找到對應的卡應用後就可以進行數據交互,交互的數據一般是密文,不聯機解密的話,用對稱算法,聯機解密的話,用非對稱和對稱算法都行。
HCE是軟件模擬的智能IC卡,所以也會有AID。本文CardEmulation只注冊一個AID。本文的代碼改自Android 4.4 Sample,沒改動CardEmulation,簡化CardReader並支持Android 2.3系統,適應低版本的NFC手機做虛擬卡的卡讀取了。使用努比亞Z7 MAX做CardEmulation,小米 2A作CardReader。本文的代碼可以到http://pan.baidu.com/s/1o6JnXr0下載。個人覺得閱讀CardReader核心代碼更能了解2者交互的過程:
[java] view plaincopyprint?
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 intent
TECHLISTS = 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 device
isoDep.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 device
Log.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 number
String accountNumber = new String(payload, "UTF-8");
Log.i(TAG, "Received: " + accountNumber);
// Inform CardReaderFragment of received account number
return accountNumber;
}
} catch (IOException e) {
Log.e(TAG, "Error communicating with card: " + e.toString());
}
}
return null;
}
public static String load(Parcelable parcelable) {
// 從Parcelable篩選出各類NFC標准數據
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);
}