Strength in Complexity?

[Ben Laurie]

Arshad Noor wrote:
> Florian Weimer wrote:
>> * Arshad Noor:
>>>
>>> http://www.informationweek.com/shared/printableArticle.jhtml?articleID=208800937 
>>>
>>
>> On a more serious note, I think the criticism probably refers to the
>> fact that SKSML does not cryptopgrahically enforce proper key
>> management.  If a participant turns bad (for instance, by storing key
>> material longer than permitted by the protocol), there's nothing in the
>> protocol that stops them.
> 
> Thank you for your comment, Florian.
> 
> I may be a little naive, but can a protocol itself enforce proper
> key-management?  I can certainly see it facilitating the required
> discipline, but I can't see how a protocol alone can enforce it.
> Any examples you can cite where this has been done, would be very
> helpful.

I find the question difficult to understand. Before I could even begin 
to answer, you'd have to define what "proper key management" actually is.

That said, EKMI (from my brief reading) has a view of key management 
that is only "proper" in quite constrained circumstances. In particular, 
keys are available to participants other than those who are 
communicating, which is general considered to be a very bad idea. This 
is fine if you are a corporation wanting to achieve escrow, of course. 
Though that can be done without requiring a central server to remember 
all the keys, of course.

> The design paradigm we chose for EKMI was to have:
> 
> 1) the centralized server be the focal point for defining policy;
> 2) the protocol carry the payload with its corresponding policy;
> 3) and the client library enforce the policy on client devices;
> 
> In some form or another, don't all cryptographic systems follow a
> similar paradigm?

Well. You said "centralized server". Many cryptographic systems don't 
have one of those.

Also, the idea of a client library enforcing policy is DRM all over 
again. Which, as we all know, will never work.

So, in short: no, they don't.

> Arshad Noor
> StrongAuth, Inc.
> 
> P.S. Companies deploying an EKMI must have an external process in
> place to ensure their applications are using "verified" libraries
> on the client devices, so their polices are not subverted.

Ha ha. Like that's going to work. Even if we assume that libraries are 
verified (fat chance, IMO), how are you going to stop, for example, 
cut'n'paste? Employees reading things out over the phone? Bugs? Etc.

Cheers,

Ben.

-- 
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"There is no limit to what a man can do or how far he can go if he
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