commit 5d9408714ce21db2afb9b8d135398c6cff96e135
author David Benjamin <davidben@google.com> Sat Jan 20 09:15:11 2018 -0500
committer Adam Langley <agl@google.com> Tue Jan 23 21:08:39 2018 +0000
tree abb91d63f4cda1f8dab7743e3ee14ee7e19a2ca0
parent 4111dd2fc215e49ff3b01e735da087ee72779758

Remove unnecessary window size cases.

The optimization for wsize = 1 only kicks in for 19-bit primes. The
cases for b >= 800 and cannot happen due to EC_MAX_SCALAR_BYTES.

Change-Id: If5ca908563f027172cdf31c9a22342152fecd12f
Reviewed-on: https://boringssl-review.googlesource.com/25145
Reviewed-by: Adam Langley <agl@google.com>

crypto/fipsmodule/ec/wnaf.c

diff --git a/crypto/fipsmodule/ec/wnaf.c b/crypto/fipsmodule/ec/wnaf.c
index d0a79f7..a1cff94 100644
--- a/crypto/fipsmodule/ec/wnaf.c
+++ b/crypto/fipsmodule/ec/wnaf.c
@@ -208,14 +208,6 @@
 //       sometimes smaller windows will give better performance
 //       (thus the boundaries should be increased)
 static size_t window_bits_for_scalar_size(size_t b) {
-  if (b >= 2000) {
-    return 6;
-  }
-
-  if (b >= 800) {
-    return 5;
-  }
-
   if (b >= 300) {
     return 4;
   }
@@ -369,15 +361,13 @@
       goto err;
     }
 
-    if (wsize > 1) {
-      if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx)) {
+    if (!EC_POINT_dbl(group, tmp, val_sub[i][0], ctx)) {
+      goto err;
+    }
+    for (j = 1; j < ((size_t)1 << (wsize - 1)); j++) {
+      if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx)) {
         goto err;
       }
-      for (j = 1; j < ((size_t)1 << (wsize - 1)); j++) {
-        if (!EC_POINT_add(group, val_sub[i][j], val_sub[i][j - 1], tmp, ctx)) {
-          goto err;
-        }
-      }
     }
   }