add instance UID

APPLICATION.MD

@@ -48,11 +48,17 @@ SW 0x6985 is returned. All tagged data structures are encoded in the [BER-TLV fo
 * P1 = 0x04
 * P2 = 0x00
 * Data = 53746174757357616C6C6574417070 (hex)
-* Response = The public key used to establish the SecureChannel
+* Response = Application Info Template
+
+Response Data format:
+- Tag 0xA4 = Application Info Template
+ - Tag 0xC0 = Instance UID (16 bytes)
+ - Tag 0x80 = ECC public Key
 
 The SELECT command is documented in the ISO 7816-4 specifications and is used to select the application on the card,
-making it the active one. The data field is the AID of the application. The response is the public key which must
+making it the active one. The data field is the AID of the application. The response is the Application Info template
-be used by the client to establish the Secure Channel.
+which contains the instance UID (which can be used by the client to keep track of multiple cards) and the public key 
+which must be used by the client to establish the Secure Channel.
 
 ### OPEN SECURE CHANNEL
 

src/main/java/im/status/wallet/SecureChannel.java

@@ -233,7 +233,7 @@ public class SecureChannel {
    * @param off the offset in the buffer
    * @return the length of the public key
    */
-  public short copyPublicKey(byte[] buf, byte off) {
+  public short copyPublicKey(byte[] buf, short off) {
     ECPublicKey pk = (ECPublicKey) scKeypair.getPublic();
     return pk.getW(buf, off);
   }

src/main/java/im/status/wallet/WalletApplet.java

@@ -24,6 +24,7 @@ public class WalletApplet extends Applet {
   static final byte PIN_MAX_RETRIES = 3;
   static final byte KEY_PATH_MAX_DEPTH = 10;
   static final byte PAIRING_MAX_CLIENT_COUNT = 5;
+  static final byte UID_LENGTH = 16;
 
   static final short EC_KEY_SIZE = 256;
   static final short CHAIN_CODE_SIZE = 32;
@@ -70,11 +71,15 @@ public class WalletApplet extends Applet {
   static final byte TLV_KEY_INITIALIZATION_STATUS = (byte) 0xC2;
   static final byte TLV_PUBLIC_KEY_DERIVATION = (byte) 0xC3;
 
+  static final byte TLV_APPLICATION_INFO_TEMPLATE = (byte) 0xA4;
+  static final byte TLV_UID = (byte) 0xC0;
+
   private static final byte[] ASSISTED_DERIVATION_HASH = {(byte) 0xAA, (byte) 0x2D, (byte) 0xA9, (byte) 0x9D, (byte) 0x91, (byte) 0x8C, (byte) 0x7D, (byte) 0x95, (byte) 0xB8, (byte) 0x96, (byte) 0x89, (byte) 0x87, (byte) 0x3E, (byte) 0xAA, (byte) 0x37, (byte) 0x67, (byte) 0x25, (byte) 0x0C, (byte) 0xFF, (byte) 0x50, (byte) 0x13, (byte) 0x9A, (byte) 0x2F, (byte) 0x87, (byte) 0xBB, (byte) 0x4F, (byte) 0xCA, (byte) 0xB4, (byte) 0xAE, (byte) 0xC3, (byte) 0xE8, (byte) 0x90};
   private static final byte[] WHISPER_KEY_PATH = {0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x01};
 
   private OwnerPIN pin;
   private OwnerPIN puk;
+  private byte[] uid;
   private SecureChannel secureChannel;
 
   private ECPublicKey masterPublic;
@@ -122,6 +127,9 @@ public class WalletApplet extends Applet {
     Crypto.init();
     SECP256k1.init();
 
+    uid = new byte[UID_LENGTH];
+    Crypto.random.generateData(uid, (short) 0, UID_LENGTH);
+
     masterPublic = (ECPublicKey) KeyBuilder.buildKey(KeyBuilder.TYPE_EC_FP_PUBLIC, EC_KEY_SIZE, false);
     masterPrivate = (ECPrivateKey) KeyBuilder.buildKey(KeyBuilder.TYPE_EC_FP_PRIVATE, EC_KEY_SIZE, false);
     masterChainCode = new byte[CHAIN_CODE_SIZE];
@@ -246,8 +254,17 @@ public class WalletApplet extends Applet {
     puk.reset();
 
     apdu.setIncomingAndReceive();
-    short keyLength = secureChannel.copyPublicKey(apdu.getBuffer(), ISO7816.OFFSET_CDATA);
+    byte[] apduBuffer = apdu.getBuffer();
-    apdu.setOutgoingAndSend(ISO7816.OFFSET_CDATA, keyLength);
+
+    apduBuffer[0] = TLV_APPLICATION_INFO_TEMPLATE;
+    apduBuffer[2] = TLV_UID;
+    apduBuffer[3] = UID_LENGTH;
+    Util.arrayCopyNonAtomic(uid, (short) 0, apduBuffer, (short) 4, UID_LENGTH);
+    apduBuffer[(short)(UID_LENGTH + 4)] = TLV_PUB_KEY;
+    short keyLength = secureChannel.copyPublicKey(apduBuffer, (short) (UID_LENGTH + 6));
+    apduBuffer[(short)(UID_LENGTH + 5)] = (byte) keyLength;
+    apduBuffer[1] = (byte)(keyLength + UID_LENGTH + 4);
+    apdu.setOutgoingAndSend((short) 0, (short)(apduBuffer[1] + 2));
   }
 
   /**

src/test/java/im/status/wallet/WalletAppletTest.java

@@ -84,7 +84,7 @@ public class WalletAppletTest {
   void init() throws CardException {
     reset();
     cmdSet = new WalletAppletCommandSet(apduChannel);
-    byte[] keyData = cmdSet.select().getData();
+    byte[] keyData = extractPublicKeyFromSelect(cmdSet.select().getData());
     secureChannel = new SecureChannelSession(keyData);
     cmdSet.setSecureChannel(secureChannel);
     cmdSet.autoPair(sha256("123456789012".getBytes()));
@@ -855,6 +855,14 @@ public class WalletAppletTest {
     return Arrays.copyOfRange(sig, 5, 5 + sig[4]);
   }
 
+  private byte[] extractPublicKeyFromSelect(byte[] select) {
+    assertEquals(WalletApplet.TLV_APPLICATION_INFO_TEMPLATE, select[0]);
+    assertEquals(WalletApplet.TLV_UID, select[2]);
+    assertEquals(WalletApplet.TLV_PUB_KEY, select[20]);
+
+    return Arrays.copyOfRange(select, 22, select.length);
+  }
+
   private void reset() {
     if (USE_SIMULATOR) {
       simulator.reset();