[AG-TECH] AG Security

[Deb Agarwal]

Stephen,

Just my 2 cents worth on the topic.

We do not have an implementation ready to distribute yet, but we
are working on distributed key agreement that will work as you say.
The venues server can act as the authorization server and then the
participants do distributed key agreement using our protocol.  This way
the venues server only (or whatever you want to use for authorization)
only needs to know public keys that are authorized at most and normally
only knows distinguished names and a trusted CA.  If you want to look
at our work so far, the pointer is www-itg.lbl.gov/CIF/GroupComm.

Deb

S.Booth wrote:
> On Fri, 19 Jul 2002, Ivan R. Judson wrote:
> 
> 
>>Hey Stephen,
>>
>>I'm not sure I follow your argument below:
>>
>>
>>>This implies that the encryption key is generated by the 
>>>venues server and we therefore have to trust the venues 
>>>server (not that we don't trust you but its the principle of 
>>>the thing) An alternative model would be that the meeting 
>>>organiser generated a token for each expected participant 
>>>containing the encryption key and the time of the meeting. 
>>>The token is public key encrypted. These can then be stored 
>>>on the venues server, sent by email, stored on a public 
>>>website whatever.
>>
>>I think having an automated mechanism for doing key distribution is the
>>goal, whether that's done via the venues server (which makes sense in
>>the ivory tower model), or other means is definitely open to discussion.
>>
>>
>>My personal model for this moving into the future is that a venue is
>>something somebody or some group owns.  That means that person or group
>>can alter "permissions" on the venue, ie, who's allowed to enter/exit,
>>modify the venue, introduce new applicaions, services, etc.  This
>>requires identification and authorization.
>>
>>Currently, we haven't integrated the notion of users into the AG
>>completely.  If we did there might be a richer set of data to use for
>>exploring different identity and authorization mechanisms.
>>
>>Getting back to your point, I think it makes infinitely more sense to
>>say,
>>
>>The participants for this private meeting are:
>>
>>Ivan
>>Stephen
>>Bob
>>Jennifer
>>
>>And have some mechanism in place to "lock" other participants out of a
>>venue, in addition to "throwing them out" of a venue they don't belong
>>in.  In addition, I think the metaphor is "private meeting" not
>>"encrypting streams", the mechanisms for making a meeting private
>>include encrypting streams, but also allocating different multicast
>>addresses for each meeting, or perhaps other more creative things.
>>
>>Does that make sense?
>>
>>--Ivan
>>
>>PS -- I don't find the ACL to be the problem in the current model, I
>>find the problem is Bob is the only one who can edit it to be the real
>>problem :-).  That being said, we've just institued a policy whereby bob
>>no longer can have vacation since he's so critical to this part...NOT
>>
> 
> 
> 
> I think you are entirely right about the model for the user interface
> model. You integrate with a booking system and select participants from
> the database. The nsca scheduler already does this.
> I'm more concerned with how you would implement this
> interface in a secure fashion. OK the probability of someone trying to
> break AG is low but cryptography is fun.
> 
> Imagine you modify the ncsa scheduler to optionally supply a randomly
> generated session key to booked sessions.
> Lets think how you would break this system. Assuming we don't have the
> compute power to brute force the session key the next obvious step is to
> try to hack into a system that has the key. Obviously any one of the
> meeting participants would do, but if the key was originally generated by
> the scheduler this becomes the most attractive target to attack as you
> could subvert the code that generated the key and gain access to ALL
> private sessions. On the other hand if the scheduler only holds a database 
> of public-keys for AG users and public-key encrypted session keys are
> generated on the home machine of the person making the booking then
> uploaded to the scheduler the user interface looks the same but the
> security risk is much less.
> 
> Of course this is probably overkill for most AG users. Maybe we should
> just lobby for a single dialog box on the event server to make it easier
> to set the session key by hand, then tell people to exchange keys by
> secure email. If you are not paranoid you probably don't care about
> encryption. If you are then you won't trust an automated system anyway :-)
> 
> 
> 
> 				Stephen
> ======================================================================
> |epcc| Dr Stephen P Booth             Project Manager           |epcc|
> |epcc| s.booth at epcc.ed.ac.uk          Phone 0131 650 5746       |epcc|
> ======================================================================
> 
> 
> 
> 


-- 
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Deb Agarwal                          e-mail:DAAgarwal at lbl.gov
MS50B-2239                           phone :(510)486-7078
Lawrence Berkeley National Lab       URL: http://www-itg.lbl.gov/~deba
Berkeley, CA 94720
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