From 1a4acc18be3a8923aafcd7d3f46a08e2b4c2e6a2 Mon Sep 17 00:00:00 2001
From: Mike Hearn <hearn@google.com>
Date: Thu, 26 Jan 2012 18:40:24 +0100
Subject: [PATCH] Pubkeys are 65 bytes, not 32.

---
 src/com/google/bitcoin/core/ECKey.java |  7 +++++--
 src/com/google/bitcoin/core/Utils.java | 14 ++++++++------
 2 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/src/com/google/bitcoin/core/ECKey.java b/src/com/google/bitcoin/core/ECKey.java
index d3290823..b790f9d1 100644
--- a/src/com/google/bitcoin/core/ECKey.java
+++ b/src/com/google/bitcoin/core/ECKey.java
@@ -129,7 +129,10 @@ public class ECKey implements Serializable {
             // Derive public from private.
             this.pub = publicKeyFromPrivate(privKey);
         } else if (pubKey != null) {
-            this.pub = Utils.bigIntegerTo32Bytes(pubKey);
+            // We expect the pubkey to be in regular encoded form, just as a BigInteger. Therefore the first byte is
+            // a special marker byte.
+            // TODO: This is probably not a useful API and may be confusing.
+            this.pub = Utils.bigIntegerToBytes(pubKey, 65);
         }
     }
 
@@ -278,7 +281,7 @@ public class ECKey implements Serializable {
      * Returns a 32 byte array containing the private key.
      */
     public byte[] getPrivKeyBytes() {
-        return Utils.bigIntegerTo32Bytes(priv);
+        return Utils.bigIntegerToBytes(priv, 32);
     }
     
     public static ECKey fromPrivKeyBytes(byte[] bytes) {
diff --git a/src/com/google/bitcoin/core/Utils.java b/src/com/google/bitcoin/core/Utils.java
index d694a349..af8d7495 100644
--- a/src/com/google/bitcoin/core/Utils.java
+++ b/src/com/google/bitcoin/core/Utils.java
@@ -64,15 +64,17 @@ public class Utils {
     /**
      * The regular {@link java.math.BigInteger#toByteArray()} method isn't quite what we often need: it appends a
      * leading zero to indicate that the number is positive and may need padding.
-     * @param b
+     *
+     * @param b the integer to format into a byte array
+     * @param numBytes the desired size of the resulting byte array
      * @return 32 byte long array.
      */
-    public static byte[] bigIntegerTo32Bytes(BigInteger b) {
-        byte[] bytes = new byte[32];
+    public static byte[] bigIntegerToBytes(BigInteger b, int numBytes) {
+        byte[] bytes = new byte[numBytes];
         byte[] biBytes = b.toByteArray();
-        int start = (biBytes.length == 33) ? 1 : 0;
-        int length = Math.min(biBytes.length, 32);
-        System.arraycopy(biBytes, start, bytes, 32 - length, length);
+        int start = (biBytes.length == numBytes + 1) ? 1 : 0;
+        int length = Math.min(biBytes.length, numBytes);
+        System.arraycopy(biBytes, start, bytes, numBytes - length, length);
         return bytes;        
     }