From 930515e496eea3e7c012ef26ffb072672f27b195 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Anton=C3=ADn=20Dufka?= <xdufka1@fi.muni.cz>
Date: Sun, 24 Sep 2023 19:27:32 +0200
Subject: [PATCH] feat: add an instruction for querying group key

---
 README.md                                  | 1 +
 applet/src/main/java/jcfrost/Consts.java   | 1 +
 applet/src/main/java/jcfrost/JCFROST.java  | 9 +++++++++
 applet/src/test/java/tests/AppletTest.java | 6 ++++++
 4 files changed, 17 insertions(+)

diff --git a/README.md b/README.md
index 1d486dc..adba77b 100644
--- a/README.md
+++ b/README.md
@@ -46,5 +46,6 @@ The applet responds to the following APDUs.
 | `COMMITMENT` | 0x00  | 0x03  | `idx`        | 0x00       | hiding commitment + binding commitment of party `idx`          |
 | `SIGN`       | 0x00  | 0x04  | msg length   | 0x00       | message                                                        |
 | `RESET`      | 0x00  | 0x05  | 0x00         | 0x00       | ---                                                            |
+| `GROUP_KEY`  | 0x00  | 0x06  | 0x00         | 0x00       | ---                                                            |
 
 The applet expects that commitments supplied by the `COMMITMENT` instruction are ordered by party `idx`, including the card's commitments.
diff --git a/applet/src/main/java/jcfrost/Consts.java b/applet/src/main/java/jcfrost/Consts.java
index 1c5c338..c5fa6fe 100644
--- a/applet/src/main/java/jcfrost/Consts.java
+++ b/applet/src/main/java/jcfrost/Consts.java
@@ -9,6 +9,7 @@ public class Consts {
     public static final byte INS_SIGN = (byte) 0x04;
 
     public static final byte INS_RESET = (byte) 0x05;
+    public static final byte INS_GROUP_KEY = (byte) 0x06;
 
     public final static short E_ALREADY_INITIALIZED = (short) 0xee00;
     public final static short E_UNINITIALIZED = (short) 0xee01;
diff --git a/applet/src/main/java/jcfrost/JCFROST.java b/applet/src/main/java/jcfrost/JCFROST.java
index 179bb7f..3b115ee 100755
--- a/applet/src/main/java/jcfrost/JCFROST.java
+++ b/applet/src/main/java/jcfrost/JCFROST.java
@@ -67,6 +67,10 @@ public void process(APDU apdu) {
                     reset(apdu);
                     break;
 
+                case Consts.INS_GROUP_KEY:
+                    getGroupKey(apdu);
+                    break;
+
                 default:
                     ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
             }
@@ -167,4 +171,9 @@ private void reset(APDU apdu) {
         frost.reset();
         apdu.setOutgoing();
     }
+
+    private void getGroupKey(APDU apdu) {
+        short len = groupPublic.encode(apdu.getBuffer(), (short) 0, true);
+        apdu.setOutgoingAndSend((short) 0, len);
+    }
 }
diff --git a/applet/src/test/java/tests/AppletTest.java b/applet/src/test/java/tests/AppletTest.java
index fb746cb..16f0eae 100755
--- a/applet/src/test/java/tests/AppletTest.java
+++ b/applet/src/test/java/tests/AppletTest.java
@@ -65,6 +65,11 @@ public ResponseAPDU reset(CardManager cm) throws CardException {
         return cm.transmit(cmd);
     }
 
+    public ResponseAPDU groupKey(CardManager cm) throws CardException {
+        final CommandAPDU cmd = new CommandAPDU(Consts.CLA_JCFROST, Consts.INS_GROUP_KEY, 0, 0);
+        return cm.transmit(cmd);
+    }
+
     @Test
     public void testSetup() throws Exception {
         CardManager cm = connect();
@@ -79,6 +84,7 @@ public void testSetup() throws Exception {
             );
             Assert.assertArrayEquals(responseAPDU.getData(), expected);
         }
+        Assert.assertArrayEquals(tv.groupKey(), groupKey(cm).getData());
         reset(cm);
     }