Path: utzoo!mnetor!uunet!husc6!think!ames!pasteur!ucbvax!BOSCO.BERKELEY.EDU!gsmith
From: gsmith@BOSCO.BERKELEY.EDU
Newsgroups: news.admin
Subject: Re: Bizarre authentication scheme
Message-ID: <8802210319.AA00406@maypo>
Date: 21 Feb 88 03:19:30 GMT
References: <8802080327.AA02920@jiff> <425@prlb2.UUCP>
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: maypo!gsmith (Gene Ward Smith)
Organization: Bosco Gang Chocolate Center
Lines: 42
Keywords: 10371664694678927135158569960683451164025292213568271978668183

In article <425@prlb2.UUCP> quisquat@prlb2.UUCP (Jean-Jac. Quisquater) writes:

>In article <8802080327.AA02920@jiff> gsmith@brahms.BERKELEY.EDU () writes:
>> If anyone feels strongly enough about protection against
>>forgeries, one system which does not involve any fixes by anyone
>>but the user himself is to post a large number which is the
>>product of two large enough (say, ~10^30) primes or pseudoprimes.
>>In any subsequent article you wish to authenticate, you give a
>>pointer to the previous article and the factorization. Then you
>>supply a new composite number.

>Incorrect.

  This can't be incorrect, because it was not a statement of
fact, but a proposal. There seems to be a good deal of confusion
over what such a scheme would be intended to accomplish:
certainly, I did not believe (nor state) that this would give any
absolute protection against forgeries, or that the "Gene Smith"
for whose continuity of identity this system would attempt to
supply publically available evidence was ipso facto and by that
test *alone* the "real" one, etc.

>(1) Your number (1037...183) must be really related to the message you
>send. Otherwise, If I copy the header of your article using some forgery,
>your scheme permits also to authenticate my message. That is, you need a true
>signature scheme with shadow or imprint.

  I confess I don't understand you at all. Can you explain, or
perhaps demonstrate, your point? Can you show that you are "Gene
Smith", in other words?

>(2) I can also forge any message including a large number. In any subsequent
>article I give a pointer to this article and the factorization. The only
>thing you can prove is: ``Somebody knows the factorization: nothing else!''.

  Again, I don't follow at all. Are you proving you are "Gene
Smith" by quoting a factorization I have already published? You
really should be located closer to Berkeley than you are for this
to work, I would think.  Am I missing something?

ucbvax!brahms!gsmith    Gene Ward Smith/Brahms Gang/Berkeley CA 94720
ucbvax!bosco!gsmith            "When Ubizmo talks, people listen."