From f259c7ebd7e2e7a77b3ba492902f30d3e581c83b Mon Sep 17 00:00:00 2001
From: Stefan Thomas <justmoon@members.fsf.org>
Date: Sat, 21 Sep 2013 17:16:44 -0700
Subject: [PATCH] Montgomery: Fix infinite loop for leading zero inputs. Add
 test.

---
 src/js/sjcl-custom/sjcl-montgomery.js | 5 +++--
 test/sjcl-montgomery.js               | 8 ++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/js/sjcl-custom/sjcl-montgomery.js b/src/js/sjcl-custom/sjcl-montgomery.js
index c44fa9f5..f1d66dee 100644
--- a/src/js/sjcl-custom/sjcl-montgomery.js
+++ b/src/js/sjcl-custom/sjcl-montgomery.js
@@ -68,10 +68,9 @@ Montgomery.prototype.reduce = function (x)
     while (x.limbs[j] >= radixMod) { x.limbs[j] -= radixMod; x.limbs[++j]++; }
   }
   x.trim();
-  x.fullReduce();
   x = x.shiftRight(this.mt * this.m.radix);
   if (x.greaterEquals(this.m)) x = x.sub(this.m);
-  return x;
+  return x.trim().normalize().reduce();
 };
 
 Montgomery.prototype.square = function (x)
@@ -113,6 +112,8 @@ sjcl.bn.prototype.powermodMontgomery = function (e, m)
 
   var z = new Montgomery(m);
 
+  e.trim().normalize();
+
   // precomputation
   var g = new Array(), n = 3, k1 = k-1, km = (1<<k)-1;
   g[1] = z.convert(this);
diff --git a/test/sjcl-montgomery.js b/test/sjcl-montgomery.js
index 64376607..d6abe478 100644
--- a/test/sjcl-montgomery.js
+++ b/test/sjcl-montgomery.js
@@ -76,10 +76,10 @@ describe('SJCL Montgomery Exponentiation', function() {
     });
     it('test 9', function () {
       testExp({
-        g: "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",
-        e: "322e393f76a1c22b147e7d193c00c023afb7c1500b006ff1bc1cc8d391fc38bd",
-        m: "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",
-        r: "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"
+        g: "4c3399bebab284bc7f9056efe17ea39db324ffa1d52dc1542eb16a749570789359f192535b7bcb514b36be9cdb4fb2a6ba3ad6b4248034e9a1d2a8612cd9d885242b4f679524121b74f79d7db14859fccde1c0dfe6ef002dcbc777ab5fcf4432",
+        e: "000322e6b6dafe138ccd6a991977d19",
+        m: "a5091daa41997943e3c98469e93377f668d05d8059bc53f72aaacdac3729a3070dc7439a5171160bf9ec2826b7191b03b0e84b28e14dd376de35d29a96f686666e053ab62a41ebc2b5f52e8cf06254100fd153a1cda4485f170c39c54689e52d",
+        r: "554336ea044782d29f091117cfeaeee2334b4242bd7428d0bba3ce5325781dc219e891e54698cb0193ffe7c6fc07f1808f6685e64b6a082815f6afd2e16c7a61316b5e3e59cd8b3984d5a76c8e173f8615f7dceac0c99e27e4abfb1278dfa67f"
       });
     });
   });