From f5a5231c7242480215de673560b9a33c033419f5 Mon Sep 17 00:00:00 2001
From: Joost Rijneveld <joost@joostrijneveld.nl>
Date: Wed, 28 Oct 2015 13:45:05 +0100
Subject: [PATCH] Do not perform bds_round for the last leaf

---
 xmss_fast.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/xmss_fast.c b/xmss_fast.c
index 5aa8a04..62a6f48 100644
--- a/xmss_fast.c
+++ b/xmss_fast.c
@@ -690,7 +690,10 @@ int xmss_sign(unsigned char *sk, bds_state *state, unsigned char *sig_msg, unsig
   // the auth path was already computed during the previous round
   memcpy(sig_msg, state->auth, h*n);
 
-  bds_round(state, idx, sk_seed, params, (h - k) >> 1, pub_seed, ots_addr);
+  if (idx < (1 << h) - 1) {
+    bds_round(state, idx, sk_seed, params, (h - k) >> 1, pub_seed, ots_addr);
+  }
+
   sig_msg += params->h*n;
   *sig_msg_len += params->h*n;