Newsgroups: sci.crypt
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: One time pads?
Message-ID: <1988Feb23.165949.4602@utzoo.uucp>
Organization: U of Toronto Zoology
References: <4209@june.cs.washington.edu> <1988Feb15.151522.5094@utzoo.uucp>, <575@gtx.com>
Date: Tue, 23-Feb-88 16:59:29 EST

> It seems to me that potential one-time pads are broadcast every day in
> the form of newspapers, magazines, sports scores, lottery numbers,
> etc.  All you need to do is agree on some algorithm for using them.
> You can either xor strings from these sources with your message, or
> reseed a random number generator based on the broadcast data...

The trouble is that the bit stream you get from these sources is not
*random*, and a random-number generator seeded from them isn't either.
You don't get the unbreakability of the one-time pad unless your key
stream is completely random, with no pattern whatsoever.  Making it
English text, from whatever source, is about as useful as just sending
your message "in clear"; methods for cryptanalyzing that sort of thing
are old hat.  Seeding a garden-variety "random"-number generator is just
as bad.
-- 
Those who do not understand Unix are |  Henry Spencer @ U of Toronto Zoology
condemned to reinvent it, poorly.    | {allegra,ihnp4,decvax,utai}!utzoo!henry