From owner-freebsd-chat@FreeBSD.ORG Sun May 25 20:50:15 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 472751065670 for ; Sun, 25 May 2008 20:50:15 +0000 (UTC) (envelope-from aryeh.friedman@gmail.com) Received: from mta5.srv.hcvlny.cv.net (mta5.srv.hcvlny.cv.net [167.206.4.200]) by mx1.freebsd.org (Postfix) with ESMTP id 145BF8FC22 for ; Sun, 25 May 2008 20:50:15 +0000 (UTC) (envelope-from aryeh.friedman@gmail.com) Received: from ool-435559b8.dyn.optonline.net (ool-435559b8.dyn.optonline.net [67.85.89.184]) by mta5.srv.hcvlny.cv.net (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) with ESMTP id <0K1F00JJ7Z7QRBS0@mta5.srv.hcvlny.cv.net> for freebsd-chat@freebsd.org; Sun, 25 May 2008 16:50:14 -0400 (EDT) Received: from ool-435559b8.dyn.optonline.net (localhost [127.0.0.1]) by ool-435559b8.dyn.optonline.net (8.14.2/8.14.2) with ESMTP id m4PKoDol078706; Sun, 25 May 2008 16:50:13 -0400 Date: Sun, 25 May 2008 16:50:08 -0400 From: "Aryeh M. Friedman" In-reply-to: <20080525203052.GA6996@rwxrwxrwx.net> To: freebsd-chat@freebsd.org, aryeh.friedman@gmail.com Message-id: <4839D100.30405@gmail.com> MIME-version: 1.0 Content-type: text/plain; charset=UTF-8; format=flowed Content-transfer-encoding: 7BIT X-Enigmail-Version: 0.95.6 References: <4839C799.6020104@gmail.com> <20080525203052.GA6996@rwxrwxrwx.net> User-Agent: Thunderbird 2.0.0.14 (X11/20080513) Cc: 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 20:50:15 -0000 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Martin Tournoij wrote: | 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...? | If this was homework I would just use the above and take the b or what ever I would get on it but I need this for something else where any attack is not good. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkg50QAACgkQk8GFzCrQm4BA2ACcC3s3JmVzqKwFDi+l1TtwsKXe e1QAoMTBCmZi0rQueLkrGMJrzjVggWGR =1954 -----END PGP SIGNATURE-----