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Article #2889Re: Encryption plus compression (Was: Another well-intentioned novice's quest)
From: Dane C. Butzer
Date: Wed, 06 Jan 1993 21:51
Date: Wed, 06 Jan 1993 21:51
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In article <1993Jan5.195004.5453@den.mmc.com> jhull@vulcan-gw.den.mmc.com writes: >I thought that compression prior to encryption added "more than might >otherwise be expected" strength to a system because it made differential >cryptanalytic attacks difficult or impossible. > >Am I missing something here? > >--- --- --- --- --- Sorry if this has been brought up, but don't many compression programs put some type of table at the start of the compressed file (defining what characters map to what uncompressed sequences, for example)? If this is the case, doesn't this give your opponent some extra info., just like partially know plain text? This would more than compensate for the extra 2^4 or whatever factor introduced in the attacker's work function. Seems like you'd have to be careful to avoid this (although I don't know how you would). Just my $0.02 worth... Dane Butzer butzerd@ee.eng.ohio-state.edu
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Newsgroups: sci.crypt Path: arc1-ca.pugleaf.net!sparky!uunet!zaphod.mps.ohio-state.edu!sample.eng.ohio-state.edu!blanc!butzerd From: butzerd@blanc.eng.ohio-state.edu (Dane C. Butzer) Subject: Re: Encryption plus compression (Was: Another well-intentioned novice's quest) Message-ID: <1993Jan6.215140.18753@ee.eng.ohio-state.edu> Sender: news@ee.eng.ohio-state.edu Organization: The Ohio State University Dept of Electrical Engineering References: <1993Jan05.160811.29681@rchland.ibm.com> <1993Jan5.195004.5453@den.mmc.com> Date: Wed, 6 Jan 1993 21:51:40 GMT Lines: 23