🚀 go-pugleaf

In article <9208182108.AA09132@news.cis.ohio-state.edu> Marc.Ringuette@daisy.learning.cs.cmu.edu writes:
>
>The basic technique I propose in order to achieve this is a two-stage news
>distribution process, where first the news is distributed to the entire set
>of receiving machines, then signatures are collected from all receivers and
>distributed in the same way as a regular news article.  
>
>Machines must register themselves by posting to the newsgroup, and must agree
>to respond to signature requests within a reasonable window, or they will be
>removed from the set of participating hosts.  
>
>What do you think?  See any gaping holes?  Want to flesh it out and 
>give it a try?
>
>    --Marc Ringuette, mnr@cs.cmu.edu

Gaping holes?  *YES*

There is no central authentication server, so every subscriber must be
able to determine authentication themselves.  That means every
subscriber needs a list of the names of all of the other subscribers.

Any subscriber can fraudulently "authenticate" any posting simply by
greping through the list of subscribers and announcing "subscriber foo
received article 754", "subscriber bar received article 754", etc.

There is no way to defend against this because there is no way to prove
who sent the message stating that machine foo has received an article.

Worse, there is no way for any machine even to know that it has a complete
or accurate list of subscribers because there is no way to distribute
such a list in a trusted manner.

Providing a centralized server for doing the authentication wouldn't
help, because there is no way for it to know who is sending the
subscription messages or who is sending the receipt messages.  There
would also be no way for the individual subscribers to know who sent
the "article 754 authenticated" message.

If you had a mechanism that allowed you to prove who sent a message,
then you could solve not only the secure newsfeed problem but a whole
host of more serious problems.  Unfortunately, such a mechanism doesn't
exist.

Note that any proposed solution to the above problem which claims to
find an answer using any of the words DES, RSA, public-key encryption,
or private-key encryption is a non-solution.  Those are all encryption
techniques.  The problem here has nothing to do with encryption
techniques.  The problem here has to do with cryptographic protocols,
or more importantly with the lack thereof.  It is a fundamentally unsolved
and (I believe) unsolveable problem.  There is no way to propagate trust
across the entire network.

-don