From owner-freebsd-chat@FreeBSD.ORG Sun May 25 20:46:08 2008 Return-Path: Delivered-To: freebsd-chat@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 1C07F1065690 for ; Sun, 25 May 2008 20:46:08 +0000 (UTC) (envelope-from carpetsmoker@rwxrwxrwx.net) Received: from mail.rwxrwxrwx.net (rwxrwxrwx.net [82.93.23.199]) by mx1.freebsd.org (Postfix) with ESMTP id B17EC8FC1C for ; Sun, 25 May 2008 20:46:07 +0000 (UTC) (envelope-from carpetsmoker@rwxrwxrwx.net) Received: from localhost (unknown [127.0.0.1]) by mail.rwxrwxrwx.net (Postfix) with ESMTP id DE7CB6D49C for ; Sun, 25 May 2008 22:28:11 +0200 (CEST) Received: from mail.rwxrwxrwx.net ([127.0.0.1]) by localhost (mail.rwxrwxrwx.net [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id lwMCjqgQTD-x for ; Sun, 25 May 2008 22:28:08 +0200 (CEST) Received: from phong.rwxrwxrwx.net (phong [192.168.100.13]) by mail.rwxrwxrwx.net (Postfix) with SMTP id CBE756D444 for ; Sun, 25 May 2008 22:28:08 +0200 (CEST) Received: by phong.rwxrwxrwx.net (sSMTP sendmail emulation); Sun, 25 May 2008 22:30:53 +0200 From: "Martin Tournoij" Received: by phong.rwxrwxrwx.net (tmda-sendmail, from uid 1001); Sun, 25 May 2008 22:30:53 +0200 Date: Sun, 25 May 2008 22:30:52 +0200 To: freebsd-chat@freebsd.org Message-ID: <20080525203052.GA6996@rwxrwxrwx.net> References: <4839C799.6020104@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <4839C799.6020104@gmail.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-Delivery-Agent: TMDA/1.1.12 (Macallan) Mail-Followup-To: freebsd-chat@freebsd.org, aryeh.friedman@gmail.com Cc: aryeh.friedman@gmail.com Subject: Re: [OT] looking for a algorithm X-BeenThere: freebsd-chat@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Non technical items related to the community List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 25 May 2008 20:46:08 -0000 On Sun, May 25, 2008 at 04:10:01PM -0400, Aryeh M. Friedman wrote: > Lets say I have a string of n bits that needs to be filled by repeatedly > applying some function on k strings of m bits where |m|<|n|. Assuming > that m(i) is a random string and n needs to also be random what is the best > way to do this. Note it is possible that k*|m|>|n|. What I have been > thinking so far is: > > ~ Let m' be the average length of m // this is pre-computable > ~ Let n be all 0's > > ~ for i=0 --> k > ~ pos=m'*i > > ~ xor string k[i] onto n starting at pos // wrap around if needed > > ~ While this is simple I wonder if it can be attacked (determine what > k[i]) if k*|m|>|n| (it is trivial to attack if k*|m|<=|n|). Also is there > some way to make attacking hard if k*|m|<=|n|? > > ~ Ideas? So you want us to do your homework...? -- Martin Tournoij carpetsmoker@rwxrwxrwx.net http://www.daemonforums.org Information is the inverse of entropy.