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From: btb@ncoast.UUCP (Brad Banko)
Newsgroups: sci.crypt
Subject: Re: encryption with public keys
Message-ID: <1828@ncoast.UUCP>
Date: Thu, 18-Dec-86 21:17:34 EST
Article-I.D.: ncoast.1828
Posted: Thu Dec 18 21:17:34 1986
Date-Received: Sat, 20-Dec-86 03:14:16 EST
References: <3072@ihuxf.UUCP> <93@vianet.UUCP>
Reply-To: btb@ncoast.UUCP (Brad Banko)
Organization: Cleveland Public Access UNIX, Cleveland, OH
Lines: 25
Keywords: public key, cryptography, verification, electronic signatures
Summary: this is important stuff

I'm sure I won't be the first to want to clarify this for Bob Devine.
Public Key cryptography is a system where encoding and decoding are
controlled by separate keys which are hopefully underiveable from each
other even if the system is known.  Martin Gardner has discussed the
concept in Mathematical Games (I think it was him) as well as one specific
method using large prime numbers and their products for the process.

	So, what you have are two separate keys for each encryption.
One is know only to you, and the decoding key is known only to the
person that you send the encrypted message and you.  A way around this
is for two people to use each others keys:

	text => your key1 => his public key => cipher

	cipher => his key1 => your public key => text

Both your 'key1's are known only to yourselves, hence, if he gets a 
message from you, he can only decode it with your public key, and his
private key (his key1)... since only you know your key1, only you could
have sent the message... a signature.

-- 
			Brad Banko
			...!decvax!cwruecmp!ncoast!btb
			Cleveland, Ohio