Re: [secdir] FNV web site

Donald Eastlake <d3e3e3@gmail.com> Tue, 23 March 2010 19:51 UTC

Return-Path: <d3e3e3@gmail.com>
X-Original-To: secdir@core3.amsl.com
Delivered-To: secdir@core3.amsl.com
Received: from localhost (localhost [127.0.0.1]) by core3.amsl.com (Postfix) with ESMTP id B8B4B3A6784 for <secdir@core3.amsl.com>; Tue, 23 Mar 2010 12:51:36 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 1.282
X-Spam-Level: *
X-Spam-Status: No, score=1.282 tagged_above=-999 required=5 tests=[AWL=0.150, BAYES_50=0.001, DNS_FROM_OPENWHOIS=1.13, HTML_MESSAGE=0.001]
Received: from mail.ietf.org ([64.170.98.32]) by localhost (core3.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id iKitExYaoILR for <secdir@core3.amsl.com>; Tue, 23 Mar 2010 12:51:35 -0700 (PDT)
Received: from mail-wy0-f172.google.com (mail-wy0-f172.google.com [74.125.82.172]) by core3.amsl.com (Postfix) with ESMTP id 64D4F3A659A for <secdir@ietf.org>; Tue, 23 Mar 2010 12:51:35 -0700 (PDT)
Received: by wyb29 with SMTP id 29so3226118wyb.31 for <secdir@ietf.org>; Tue, 23 Mar 2010 12:51:50 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:cc:content-type; bh=MLwoASf4wkONE8gXSdiNF6y7EKClnCKsf8JJ5Nif+u8=; b=KIWMjIoZ9c2Wa3UadCFSSUIyP0COOIP00/Uu2fwtTrNIX3VpbVLu2BhWd8LzT8Hr5j IVBe0i3RCgP/CmVZwNAKUGWTMewqbamEPCIw0R0H3ZsjpFS5tu2WzhKw28OXVHRBwAT8 NNdTcfUB07s6B2OL5zQbCCCa77kQ4B8QAb16g=
DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=eQ5GcUfYGkyu81U/pFMl9Taeya9NgAM+It1KvjAK4B8DVqSTh5f7zPU+8zuXramJkw egL/tI+q+soCi90dnwJV8zoojPa2yHcRmn5AoMo4Ul2KTiQU10tMgnaJ8woOtVzUJIZ/ sa/XAZFdo5p4hf/U9ZWkA0M1p5SHvkaQvbTW4=
MIME-Version: 1.0
Received: by 10.216.89.84 with SMTP id b62mr3780328wef.226.1269373910709; Tue, 23 Mar 2010 12:51:50 -0700 (PDT)
In-Reply-To: <4BA91AD8.3060000@deployingradius.com>
References: <p0624081bc7ceca681389@10.6.19.70> <4BA91AD8.3060000@deployingradius.com>
Date: Tue, 23 Mar 2010 15:51:50 -0400
Message-ID: <1028365c1003231251j1ce360eev574b34f7fd910621@mail.gmail.com>
From: Donald Eastlake <d3e3e3@gmail.com>
To: Alan DeKok <aland@deployingradius.com>
Content-Type: multipart/alternative; boundary="0016e6d9710208ffbe04827d25ca"
Cc: secdir@ietf.org
Subject: Re: [secdir] FNV web site
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.9
Precedence: list
List-Id: Security Area Directorate <secdir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/listinfo/secdir>, <mailto:secdir-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/secdir>
List-Post: <mailto:secdir@ietf.org>
List-Help: <mailto:secdir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/secdir>, <mailto:secdir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 23 Mar 2010 19:51:36 -0000

So, couldn't you just use it to compute twice as many hash bits as you need
and then xor the top and bottom half of the output to fix this flaw?

Donald
=============================
Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
155 Beaver Street   +1-508-634-2066 (home)
Milford, MA 01757 USA
d3e3e3@gmail.com


On Tue, Mar 23, 2010 at 3:47 PM, Alan DeKok <aland@deployingradius.com>wrote:

> Paul Hoffman wrote:
> > <http://isthe.com/chongo/tech/comp/fnv/>
>
>   If hash distribution matters, see:
>
> http://sites.google.com/site/murmurhash/avalanche
> ...
> This is why you probably shouldn't use FNV. Both low bits of the hash
> and end bits of the key aren't thorougly mixed.
> ...
>
>
>  If hash distributions don't matter, FNV is very fast.
>
>  Alan DeKok.
> _______________________________________________
> secdir mailing list
> secdir@ietf.org
> https://www.ietf.org/mailman/listinfo/secdir
>