From d4d9c734c315e99136fe245c5733ca75cab9f8bf Mon Sep 17 00:00:00 2001
From: Pieter Wuille <sipa@ulyssis.org>
Date: Sun, 25 Dec 2011 15:02:31 +0100
Subject: [PATCH] Compact signatures with compressed pubkeys

---
 src/key.h | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/key.h b/src/key.h
index b6d805c0..c28222a9 100644
--- a/src/key.h
+++ b/src/key.h
@@ -236,6 +236,8 @@ public:
             {
                 CKey keyRec;
                 keyRec.fSet = true;
+                if (fCompressedPubKey)
+                    keyRec.SetCompressedPubKey();
                 if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
                     if (keyRec.GetPubKey() == this->GetPubKey())
                     {
@@ -247,7 +249,7 @@ public:
             if (nRecId == -1)
                 throw key_error("CKey::SignCompact() : unable to construct recoverable key");
 
-            vchSig[0] = nRecId+27;
+            vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
             BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
             BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
             fOk = true;
@@ -264,7 +266,8 @@ public:
     {
         if (vchSig.size() != 65)
             return false;
-        if (vchSig[0]<27 || vchSig[0]>=31)
+        int nV = vchSig[0];
+        if (nV<27 || nV>=35)
             return false;
         ECDSA_SIG *sig = ECDSA_SIG_new();
         BN_bin2bn(&vchSig[1],32,sig->r);
@@ -272,7 +275,12 @@ public:
 
         EC_KEY_free(pkey);
         pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
-        if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), vchSig[0] - 27, 0) == 1)
+        if (nV >= 31)
+        {
+            SetCompressedPubKey();
+            nV -= 4;
+        }
+        if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
         {
             fSet = true;
             ECDSA_SIG_free(sig);