From: Alberto Donizetti <alb.donizetti@gmail.com>
Date: Thu, 11 Dec 2014 18:09:39 +0000 (+0100)
Subject: math: Added parity check to ProbablyPrime
X-Git-Tag: go1.5beta1~2646
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=5de497bc6fbae2470f700bb9d786a844cd7908db;p=gostls13.git

math: Added parity check to ProbablyPrime

Fixes #9269

Change-Id: I25751632e95978537b656aedfa5c35ab2273089b
Reviewed-on: https://go-review.googlesource.com/1380
Reviewed-by: Robert Griesemer <gri@golang.org>
---

diff --git a/src/math/big/nat.go b/src/math/big/nat.go
index 16a87f5c53..6e65ea1cb4 100644
--- a/src/math/big/nat.go
+++ b/src/math/big/nat.go
@@ -1404,6 +1404,10 @@ func (n nat) probablyPrime(reps int) bool {
 		}
 	}
 
+	if n[0]&1 == 0 {
+		return false // n is even
+	}
+
 	const primesProduct32 = 0xC0CFD797         // Π {p ∈ primes, 2 < p <= 29}
 	const primesProduct64 = 0xE221F97C30E94E1D // Π {p ∈ primes, 2 < p <= 53}