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From: darrell@sdcsvax.UCSD.EDU (Darrell Long)
Newsgroups: mod.os
Subject: Re: public key doubts
Message-ID: <2876@sdcsvax.UCSD.EDU>
Date: Wed, 18-Mar-87 16:52:17 EST
Article-I.D.: sdcsvax.2876
Posted: Wed Mar 18 16:52:17 1987
Date-Received: Sat, 21-Mar-87 10:30:43 EST
Lines: 23
Approved: mod-os@sdcsvax.uucp

> With public key encryption, the enemy *by definition* can generate
> as much plaintext/ciphertext as he wishes...
> it seems to me that this puts a real (and low) time limit on how
> long one can afford to use a given public/private key pair. 

He can generate as much plaintext/ciphertext as he wishes, but it's not
going to *tell* him anything that the public key doesn't already tell him.
The whole point of known-plaintext attacks is that they make it easier to
tell how the stuff was encrypted.  With a public-key system, you already
know the encryption technique, and a known-plaintext attack doesn't buy
you anything.  That's my understanding, anyway -- I'm not an expert on this.
The real cryppies hang out :-) in sci.crypt.

				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,decvax,pyramid}!utzoo!henry



-- 
Darrell Long
Department of Computer Science & Engineering, UC San Diego, La Jolla CA 92093
ARPA: Darrell@Beowulf.UCSD.EDU  UUCP: darrell@sdcsvax.uucp
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