Date: Sun, 25 May 2008 16:50:08 -0400 From: "Aryeh M. Friedman" <aryeh.friedman@gmail.com> To: freebsd-chat@freebsd.org, aryeh.friedman@gmail.com Subject: Re: [OT] looking for a algorithm Message-ID: <4839D100.30405@gmail.com> In-Reply-To: <20080525203052.GA6996@rwxrwxrwx.net> References: <4839C799.6020104@gmail.com> <20080525203052.GA6996@rwxrwxrwx.net>
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-----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-----
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