From owner-freebsd-questions@FreeBSD.ORG Sun Sep 6 01:21:41 2009 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3B4481065692 for ; Sun, 6 Sep 2009 01:21:41 +0000 (UTC) (envelope-from vogelke@hcst.com) Received: from beta.hcst.com (beta.hcst.com [192.52.183.241]) by mx1.freebsd.org (Postfix) with ESMTP id D4CF98FC19 for ; Sun, 6 Sep 2009 01:21:40 +0000 (UTC) Received: from beta.hcst.com (localhost [127.0.0.1]) by beta.hcst.com (8.13.8/8.13.8/Debian-3) with ESMTP id n861Le30022943 for ; Sat, 5 Sep 2009 21:21:40 -0400 Received: (from vogelke@localhost) by beta.hcst.com (8.13.8/8.13.8/Submit) id n861LegG022942; Sat, 5 Sep 2009 21:21:40 -0400 Received: by kev.msw.wpafb.af.mil (Postfix, from userid 32768) id E2731B7DD; Sat, 5 Sep 2009 21:21:07 -0400 (EDT) To: freebsd-questions@freebsd.org In-reply-to: <64c038660909050933h25a91edcw56688993f5557ad2@mail.gmail.com> (message from Modulok on Sat, 5 Sep 2009 10:33:03 -0600) Organization: Oasis Systems Inc. X-Disclaimer: I don't speak for the USAF or Oasis. X-GPG-ID: 1024D/711752A0 2006-06-27 Karl Vogel X-GPG-Fingerprint: 56EB 6DBF 4224 C953 F417 CC99 4C7C 7D46 7117 52A0 Message-Id: <20090906012107.E2731B7DD@kev.msw.wpafb.af.mil> Date: Sat, 5 Sep 2009 21:21:07 -0400 (EDT) From: vogelke+unix@pobox.com (Karl Vogel) Subject: Re: Is there such thing as a 'soft checksum' tool? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: vogelke+unix@pobox.com List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 06 Sep 2009 01:21:41 -0000 >> On Sat, 5 Sep 2009 10:33:03 -0600, >> Modulok said: M> I'm looking for a pseudo-checksum tool for use with cataloging images. M> For example, a strict checksum algorithm, like the sha family, will M> produce a dramatically different checksum for two files which differ by M> only a single bit. I'm looking for something where two images, which M> are similar, get a proportionally similar checksum. This works pretty well with text, but I don't know about images. http://ixazon.dynip.com/~cmeclax/nilsimsa.html What's a nilsimsa code? A nilsimsa code is something like a hash, but unlike hashes, a small change in the message results in a small change in the nilsimsa code. Such a function is called a locality-sensitive hash. -- Karl Vogel I don't speak for the USAF or my company Garlic gum is not funny. --written on blackboard by Bart Simpson