From effb2ac2fb698fedfd009f921ea5267258af6c8f Mon Sep 17 00:00:00 2001
From: Christian Basler <chrigu.meyer@gmail.com>
Date: Wed, 10 Jun 2015 02:46:45 +0200
Subject: [PATCH] Fixing issue #4 - leading zeroes must be omitted on writing
 the coordinate components

---
 .../bitmessage/entity/payload/CryptoBox.java  | 25 +++++++++++--------
 .../bitmessage/entity/SerializationTest.java  |  3 ---
 2 files changed, 15 insertions(+), 13 deletions(-)

diff --git a/domain/src/main/java/ch/dissem/bitmessage/entity/payload/CryptoBox.java b/domain/src/main/java/ch/dissem/bitmessage/entity/payload/CryptoBox.java
index 8db2238..8fe6ff8 100644
--- a/domain/src/main/java/ch/dissem/bitmessage/entity/payload/CryptoBox.java
+++ b/domain/src/main/java/ch/dissem/bitmessage/entity/payload/CryptoBox.java
@@ -28,6 +28,7 @@ import org.bouncycastle.crypto.paddings.PKCS7Padding;
 import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
 import org.bouncycastle.crypto.params.KeyParameter;
 import org.bouncycastle.crypto.params.ParametersWithIV;
+import org.bouncycastle.math.ec.ECFieldElement;
 import org.bouncycastle.math.ec.ECPoint;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -152,16 +153,20 @@ public class CryptoBox implements Streamable {
         return buffer;
     }
 
-    private void writeWithoutMAC(OutputStream stream) throws IOException {
-        stream.write(initializationVector);
-        Encode.int16(curveType, stream);
-        byte[] x = R.getXCoord().getEncoded();
-        byte[] y = R.getYCoord().getEncoded();
-        Encode.int16(x.length, stream);
-        stream.write(x);
-        Encode.int16(y.length, stream);
-        stream.write(y);
-        stream.write(encrypted);
+    private void writeWithoutMAC(OutputStream out) throws IOException {
+        out.write(initializationVector);
+        Encode.int16(curveType, out);
+        writeCoordinateComponent(out, R.getXCoord());
+        writeCoordinateComponent(out, R.getYCoord());
+        out.write(encrypted);
+    }
+
+    private void writeCoordinateComponent(OutputStream out, ECFieldElement coord) throws IOException {
+        byte[] x = coord.getEncoded();
+        int offset = Bytes.numberOfLeadingZeros(x);
+        int length = x.length - offset;
+        Encode.int16(length, out);
+        out.write(x, offset, length);
     }
 
     @Override
diff --git a/domain/src/test/java/ch/dissem/bitmessage/entity/SerializationTest.java b/domain/src/test/java/ch/dissem/bitmessage/entity/SerializationTest.java
index 720c9bf..7e56f95 100644
--- a/domain/src/test/java/ch/dissem/bitmessage/entity/SerializationTest.java
+++ b/domain/src/test/java/ch/dissem/bitmessage/entity/SerializationTest.java
@@ -31,9 +31,6 @@ import static ch.dissem.bitmessage.entity.Plaintext.Type.MSG;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 
-/**
- * Created by chris on 28.04.15.
- */
 public class SerializationTest {
     @Test
     public void ensureGetPubkeyIsDeserializedAndSerializedCorrectly() throws IOException {