[67887] in Cypherpunks
Re: Binding cryptography - much work, little point ?
daemon@ATHENA.MIT.EDU (Adam Back)
Fri Oct 11 17:46:12 1996
Date: Fri, 11 Oct 1996 20:11:15 +0100
From: Adam Back <aba@dcs.ex.ac.uk>
To: peter.allan@aeat.co.uk
Cc: cypherpunks@toad.com, everheul@NGI.NL
In-Reply-To: <9610111223.AA02697@clare.risley.aeat.co.uk>
(peter.allan@aeat.co.uk)
Peter Allan <peter.allan@aeat.co.uk> writes:
> Eric_Verheul writes:
>
> > In our scheme any third party, which is probably never a TRP, can check
> > equality of the sessionkeys send to the primary recipient (the TRP) and
> > the second recipient (the real adressee), i.e. *without* needing secret
>
> So could anyone anyway by asking the TRP. The TRP returns a Yes/No
> answer, without disclosing the session key.
Yes, but how would you know the TRP was telling the truth? Also
asking the TRP is an online protocol with respect to the TRP.
> Is your binding scheme motivated mainly by avoiding that workload on
> the TRP ? Or by the fact that everybody might prefer a different TRP ?
The paper suggests that in one plausible implementation, the checkers
referred to could be network service providers:
from the summary of the paper posted here:
: The idea is that any third party, e.g., a network or service provider,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
: who has access to components 2, 3 and 4 (but not to any additional
: secret information) can:
: a. check whether the session keys in components 2 and 3 coincide;
: b. not determine any information on the actual session key.
This would allow for instance for a software only implementation of a
madatory key escrow system. The government in question could then
deputize ISPs to do their mandatory GAK compliance checking for them.
(Deputizing companies is a recent trend in law enforcment techniques
anyway).
This would allow for instance IP level encryption, with non-conforming
encrypted packets being dropped by all ISPs in the country in
question. Something the Singaporeans might find useful. The checking
functionality could also be added to a key escrow enabled router.
For this kind of application, binding cryptography is spot on.
Adam
[disclaimer: I'm against GAK]
--
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