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From: adam@misoft.UUCP
Newsgroups: sci.crypt
Subject: Completely Secure Encryption
Message-ID: <581@gec-mi-at.co.uk>
Date: Wed, 20-May-87 06:07:38 EDT
Article-I.D.: gec-mi-a.581
Posted: Wed May 20 06:07:38 1987
Date-Received: Sat, 23-May-87 08:32:55 EDT
Sender: news@gec-mi-at.co.uk
Reply-To: adam@gec-mi-at.co.uk (Adam Quantrill)
Organization: Marconi Instruments Ltd., St. Albans, UK
Lines: 25


	I have been thinking about the one really secure encryption technique,
where the text is exclusive-ored with a random string used once only. To
regenerate the text, the recipient uses her copy of the random string, which
had been sent previously by a secure method. The random string is discarded by
both parties.
	I am implementing a short C program to do this, but the one real pain
with this method is sending random strings to your various correspondants. So,
for a less secure method, I propose to generate the random string by exclusive-
oring any combination of n text and binary files held on computer:

e.g. exor /bin/sh /bin/crypt /etc/termcap | exor my_text

At the other end, the recipient types the same command line to decode the text.
All you have to do now is send the key (/bin/sh /bin/crypt /etc/termcap) by a 
secure method. The other caveat is that the sender's and receiver's machines 
share identical files (which is reasonably common between machines of the same 
make running the same o.s.).

Does anyone have any comments as to the security of this method? It would
obviously be more secure using a common but unique random file owned by the two
parties, in combination with the standard system files.
       -Adam.

/* If at first it don't compile, kludge, kludge again.*/