From: "David F. Ogren" <ogren@cris.com>
Date: Fri, 31 May 1996 20:56:02 +0800
To: cypherpunks@toad.com
Subject: Re: Where does your data want to go today?
Message-ID: <199605310727.DAA21108@darius.cris.com>
MIME-Version: 1.0
Content-Type: text/plain


> > >	What problems does compression before encryption have? It at least
> > >seems to work for PGP.
> > >
> > Most compression schemes put a header/index on the front of the
> > compressed data.
> > This makes recognizing the correct decryption very simple.
> > 
> > Call it a limited "known plaintext" situation.
> 

Using a random IV also limits the effectiveness of using known 
headers for "known plaintext" attacks.  Also note that a good block 
cipher isn't that vulnerable even to "known plaintext" attacks.
--
David F. Ogren
ogren@concentric.net (alternate address: dfogren@msn.com)
PGP Key ID: 0xC626E311
PGP Key Fingerprint: 24 23 CD 15 BF 8D D1 DE  81 71 84 C8 2C E0 4B 01
(public key available via server or by sending a message to
ogren@concentric.net with a subject of GETPGPKEY)