From: Steve Reid <steve@edmweb.com>
Date: Tue, 10 Sep 1996 09:36:04 +0800
To: Adam Back <aba@dcs.ex.ac.uk>
Subject: Re: towards an eternity service
In-Reply-To: <199609082212.XAA00383@server.test.net>
Message-ID: <Pine.BSF.3.91.960909131046.196B-100000@bitbucket.edmweb.com>
MIME-Version: 1.0
Content-Type: text/plain


> The other requirement for eternity is that the data should be secret
> shared.
[snip]
> As the eternity www servers don't know what the data in the shares
> they are holding is, they can't provide the indexing facility

I don't know much about secret sharing algorithms, but wouldn't the server
be able to get the other parts of the shares and know what it's serving?
The ability to get that information might affect server liability. 

With secret splitting, there is a simple way to create duress parts. I 
don't know if it's possible with secret sharing..

X is politically-incorrect data.
Y is data nobody would ever object to.
R is a truely random string of bits.

Alice has X xor R on her server.
Bob has R on his server.
Carol has X xor Y xor R on her server.
Dave has Y xor R on his server.

Alice and Bob are together distributing X. So are Dave and Carol. 
However, if someone were to say that Alice and Bob (and/or Dave and Carol)
are distibuting something politically incorrect, Alice and Carol (and Bob
and Dave) can get together and say "No, We're distributing Y. The other
person must be trying to frame me!". In fact, it's quite possible that
Alice thought she was distributing Y with Carol, and that Bob thought he
was also distributing Y with Dave. If they did not split the secrets
themselves, they may not have any knowledge of X's existence. Also, if any
one of the participants gets shut down, it's still possible to retrieve X,
Y and R by using different combinations of the remaining three
participants. This scenario could be extended to more participants and
secrets. 


=====================================================================
| Steve Reid - SysAdmin & Pres, EDM Web (http://www.edmweb.com/)    |
| Email: steve@edmweb.com   Home Page: http://www.edmweb.com/steve/ |
| PGP (2048/9F317269) Fingerprint: 11C89D1CD67287E68C09EC52443F8830 |
|          -- Disclaimer: JMHO, YMMV, TANSTAAFL, IANAL. --          |
===================================================================:)