[Ndn-interest] NDN protocol principles: no privacy?

Mon Mar 14 23:36:09 PDT 2016

Dear all,

In ICC 2016[0], we are going to present a mechanism that protects the
privacy of the user while the content router can still cache and
lookup. The proposed mechanism is based on proxy encryption.

With PROTECTOR, every user has a different key and every router holds
collection of keys, but nobody has the master key of the system.

[0] PROTECTOR: Privacy-Preserving Information Lookup in
Content-Centric Networks - Ashgar, Bernardini, Crispo
https://www.cs.auckland.ac.nz/~asghar/papers/Asghar-ICC16-PROTECTOR.pdf

2016-03-15 6:22 GMT+01:00  <Marc.Mosko at parc.com>:
>
> On Mar 14, 2016, at 9:53 PM, Tai-Lin Chu <tailinchu at gmail.com> wrote:
>
> Immutable = one data packet cannot be changed after publication.
>
> No, it is not “a single publisher will never use the same name for different
> contents” (I believe this is "uniquely named") nor “there is some
> cryptographic function possible on a packet such that one can detect if it
> changes”.
>
> Immutability is advisory here. If I start to violate immutablity in a
> distributed system where everything is assumed to be immutable, I am doomed
> to get incorrect result (I guess this sounds mandatory). I think
> immutability is a good choice overall, and it is better to state it as a
> principle so that nobody will use ndn the wrong way.
>
>
> Well, as you seemed to notice, if your system relies on an advisory feature
> for correctness, that’s a tenuous position.  That’s probably not a correct
> statement for NDN, as an end node should be able to detect (hopefully) if a
> Data object is what it expected via signature or something and try again
> with an exclusion.  however, you might not have liveness.
>
> So, my point here, is we talk about immutable objects but in truth we do not
> have them unless we use a hash-based name.  We can define that a correctly
> operating publisher will never re-use a name and it cryptographically binds
> every Data object, but that is not immutable objects.  That’s a protocol
> that generates unique objects.  Unique is not immutable. A publisher could
> have a failure that causes its sequence number to reset or a memory error
> that causes the version number to flip a bit, etc.
>
>
>
> One can build a discovery protocol over exact name matching.
>
>
> Is the table of contents immutable? I think your approach is fine and
> efficient but it is rather hard to manage in a large distributed system if
> the table is not immutable.
>
>
> If the client sends a nonced name the publisher can return a link (in the
> ccnx sense, not the routing hints) plus uniquely named data of the table of
> contents appended for efficiency (to avoid a second round trip).
>
> I would think that doing cursors over table of contents rows is much more
> efficient in a large distributed system than returning potentially large
> data objects and doing search.  If I have 100M versions of a name and I want
> to scan the data for some attribute, I think its much easier to fetch a
> partial tables of contents and pick the exact ones I want to retrieve than
> to iterate over the set using some name heuristic.
>
> This method also allows one to do discovery based on other criteria
> (attributes), such as signer keyids or other TLV fields, rather than just
> name elements.  I could, for example, do a */superman.mov/* search for all
> names with superman.mov as a name component (if that type of query was
> allowed by the protocol).  Or I could ask for only data objects that were
> manifests.
>
> Because this matching is done via an explicit discovery protocol, not as
> part of the forwarder, I have a lot of flexibility in the attributes I can
> query and the access control I can enforce.
>
> It is a design choice.  NDN (from CCNx 0.x) chose to use mandatory
> in-network discovery base solely on name components, exclusions, and tree
> traversal.  That’s ok, and one could claim that is sufficient.  CCNx 1.0
> chose to use explicit discovery protocols.  My main point in asking about
> this is to point out that in-network mandatory discovery at the forwarder
> level is not a necessary condition.
>
>
>
>
>
>
> On Mar 14, 2016, at 9:01 PM, <Marc.Mosko at parc.com> <Marc.Mosko at parc.com>
> wrote:
>
>
> On Mar 14, 2016, at 8:44 PM, Tai-Lin Chu <tailinchu at gmail.com> wrote:
>
> sure - I don't want to expose names that identify me, or expose my
> communication activities. given that, the "network" doesn't have the job of
> finding things for me by partial names - I only want to expose the details
> of my communication to a service that I have authenticated, and only when
> those details are encrypted. the "names" visible to the network in that sort
> of world just get the packets moving - and the only LPM needed is LPM in the
> FIB to get me to one or more instances of a service.
>
>
> Immutability is related to in-network discovery with LPM.  If all packets
> are immutable, and there is no in-network discovery, ndn must rely on some
> other protocol that cannot not build on top of ndn for discovery (we should
> all agree that randomly guessing a version number or a certain name is not
> going to work well as “discovery”). This devalues ndn as an “universal"
> protocol.
>
>
> Could you please define immutable?  Do you mean that a single publisher will
> never use the same name for different contents?  Is that mandatory or
> enforceable?  Or do you mean that there is some cryptographic function
> possible on a packet such that one can detect if it changes?  Are those
> cryptographic primitives mandatory in each packet?
>
> I disagree that it is a necessary condition that one have name suffix
> completion matching of a data object to an interest to facilitate discovery.
> One can build a discovery protocol over exact name matching.  I usually
> build these where the cache returns a chunked table of contents listing
> possible matches instead of the CCNx 0.x / NDN approach of having to return
> a (potentially very large) data object and walk a tree which is really only
> efficient if you expect what you want to be left-most or right-most child
> and not require iteration.
>
>
>
>
> On Mar 14, 2016, at 12:10 PM, Mark Stapp <mjs at cisco.com> wrote:
>
> interesting -
>
> On 3/14/16 11:27 AM, Burke, Jeff wrote:
>
>
> [...]
> RFC 6973 takes a nice approach, for example, by offering
>
> definitions of some technical properties and mechanisms, but not trying
> to formulate an overall definition of "privacy".
>
>
> So I can try to understand your point here - do you agree with the
>
> authors that the primary privacy concerns are those of individuals? (Or,
> more generally, are corporations people here for this discussion - a
> more generic "data owner"?)
>
>
>
> hmm - well, I don't think corporations are people, in the citizens united
> sense, but I think there's lots of commercial communication that needs to
> have the best possible protection, whether it's B2C or B2B?
>
> The editors there say
> that the body of the document, the discussion of the tradeoffs and
> alternatives, is the best way they could come up with to approach that
> abstraction. in practical terms, as you know well I think there's been
> an over-reliance on opportunistic caching in ICN generally, and as a
> result observability and correlation are defined to be positive
> properties of ICN communication rather than harmful ones.
>
>
>
> Would I be correct to parse your concerns into two pieces that may
>
> have different implications:
>
>
> - Confidentiality of request (e.g., the consumer side)
> - Confidentiality of publication (e.g., the publisher side)
>
>
> I think I have a mental image of "confidential request" - where an observer
> cannot see much beyond the routeable prefix needed to reach an instance of
> the service I want to communicate with. I'm not sure what "confidential
> publication" means, though? I think I want the replies to my requests to be
> encrypted with ephemeral, forward-secure key material, I don't want the
> names in the replies to expose any more than the names in the requests, and
> I want to be able to authenticate the service before I expose anything about
> my own identity or intentions. is that what you meant by "the publisher
> side"?
>
> [...]
>
>
> most of these six "principles" sounded like "mechanisms" to me - the
> list felt like the end of a discussion about alternatives and the best
> ways to implement an architecture, rather than the start of one. it
> sounded like "we're tired of questions about LPM in the PIT, so we're
> going to stop calling that a possible mechanism and start calling it an
> inevitable, immutable, unquestionable 'principle'".
>
>
> Well, to take LPM for an example - it's actually not mentioned in
> the
>
> principle doc that Alex sent. The principle I suspect that you are
> referring to is:
>
>
> [5] In-Network Name Discovery: Interests should be able use
> incomplete
>
> names to retrieve data packets.
>
> A consumer may not know the complete network-level name for data, as
>
> some parts of the name cannot be guessed, computed, or inferred
> beforehand. Once initial data is received, naming conventions can help
> determine complete names of other related data:
>
>
>
> * majority of interests will carry complete names
>
> * in-network name discovery expected to be used to bootstrap
>
> communication)
>
>
>
>
> Can you explain your objection in these terms?
>
>
> sure - I don't want to expose names that identify me, or expose my
> communication activities. given that, the "network" doesn't have the job of
> finding things for me by partial names - I only want to expose the details
> of my communication to a service that I have authenticated, and only when
> those details are encrypted. the "names" visible to the network in that sort
> of world just get the packets moving - and the only LPM needed is LPM in the
> FIB to get me to one or more instances of a service.
>
> Thanks,
> Mark
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