From: Adam Back <aba@dcs.ex.ac.uk>
Date: Sat, 9 Aug 1997 06:27:57 +0800
To: dlv@bwalk.dm.com
Subject: forgeries are good for you (was Re: REPOST : Un-forgeable Cancels)
In-Reply-To: <5R04ae64w165w@bwalk.dm.com>
Message-ID: <199708081827.TAA01595@server.test.net>
MIME-Version: 1.0
Content-Type: text/plain




Dimitri Vulis <dlv@bwalk.dm.com> writes:
> jbaber@mi.leeds.ac.uk writes:
> 
> > Any comments/glareing weaknesses that I have missed?
> 
> I used to think this scheme is very cool.  Later I realized it had a
> serious problem with forgeries in one's name.
>
> Suppose X forges an article in Y's name, and specifies a cancel
> lock; then Y can't cancel this forgery.

But that's cool!  Y shouldn't be able to cancel the forgery ... he
didn't write it.  That's the definition of censorship, removing some
one else's content.

I mean this seriously.  People should stop misplacing any value on
>From fields.  You need to use digital signatures to recognize
persistent personas.

The quicker people realise this the better.

It is in cypherpunks interests to see as many forgeries as possible.
Because then the natural solution is for people to use digital
signatures.  More people using crypto, the harder it is to outlaw.

(Dimitri: perhaps you need to code some easy to use high quality
forgery software to go with your cancel bot).

> The retraction server which David is reported to be working on
> doesn't rely on passwords on authenticate Y; if Y can demonstrate
> the ability to receive a cookie sent to Y, then the server can issue
> a signed 'hide' NoCeM for an article that purports to be from Y.
> Works for forgeries too.

(David = David Formosa?)

What's the point of this?  To provide a way to stop unsophisticated
forgeries without needing NoCeM support in the client? 

I guess it would work well enough, but it's really a bit centralised.
The operator of the retraction server might be over trusted by a lot
of people.  If the operator turns out to be untrustworthy, or
whatever, you're out of luck.

Also break into his machine and steal his secret key and you could
have a _lot_ of fun.  And it's only one machine, what if his security
isn't up to much.

Think decentralised.  That's the whole advantage NoCeM, it's
decentralised approach to providing a third party USENET news article
rating system.

Adam
-- 
Have *you* exported RSA today? --> http://www.dcs.ex.ac.uk/~aba/rsa/

print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<>
)]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`