Re: [Secdispatch] [Lake] LAKE next steps

Göran Selander <goran.selander@ericsson.com> Thu, 22 August 2019 13:27 UTC

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From: =?utf-8?B?R8O2cmFuIFNlbGFuZGVy?= <goran.selander@ericsson.com>
To: "lake@ietf.org" <lake@ietf.org>
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Thread-Topic: [Lake] LAKE next steps
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Date: Thu, 22 Aug 2019 13:27:49 +0000
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Subject: Re: [Secdispatch] [Lake] LAKE next steps
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Hi Ben and Roman, 

If I understand right, the proposal is - in one sentence - to work both on a lightweight authenticated key exchange for OSCORE in the LAKE WG, and on a compact variant of TLS in the TLS WG. This sounds like a good way forward, since an optimal solution to one of the problems is most likely not optimal (or even suitable) for the other, and optimization is one of the reasons for doing this work in the first place.

The proposed charter looks fine, I only have one comment on the text, see below. In particular I don't think there is any need to further detail requirements in the charter since those can be agreed with the listed stakeholders as part of the work.

Excerpt from proposed charter:

'The working group will collaborate and coordinate with other IETF WGs
such as ACE, CORE, 6TISCH, and LPWAN to understand and validate the
requirements and solution.  The WG will also evaluate work from
the TLS WG and derivatives thereof, and draft-selander-ace-cose-ecdhe.'

My comment is on the last sentence above. I already commented on this sentence in a previous draft of the charter:
https://mailarchive.ietf.org/arch/msg/secdispatch/xJTkOA6zfU0TcQPMYevg8IBUSVk

Additionally, I don't think this sentence well reflects the text in your mail:

'From we’ve seen so far, EDHOC seems like the leading contender, especially with respect to the “reuse of COSE algorithms” proposed requirement, but we of course welcome further data (such as on the relative code footprint of core cryptographic primitives vs. protocol integration for COSE/cTLS/etc.).'

Detailed comments:
1. It is fine that the WG also evaluates work from the TLS WG, with the obvious restriction that only solutions that are ready and complies with the requirements need to be evaluated. As long as we agree on that, there is no need to change the charter on this point. 
2. Please move ", and draft-selander-ace-cose-ecdhe" from this sentence and include it in a sentence before this one indicating that it is currently the only specified AKE for OSCORE. 

Thanks
Göran


On 2019-08-20, 17:50, "Lake on behalf of Benjamin Kaduk" <lake-bounces@ietf.org on behalf of kaduk@mit.edu> wrote:

    Thank you to everyone who attended the LAKE BoF session! It was a
    productive meeting that highlighted the community’s needs for work in this
    space.  A key insight that emerged during the session was that there is a
    fairly clear split between the “AKE for OSCORE” case and “general purpose
    lightweight AKE” in terms of the set of requirements.  We are happy to note
    a strong level of interest in a TLS-based solution that removes unnecessary
    protocol fields and encoding redundancy, which has significant potential
    for use in protocols that do not require traditional TLS cross-version
    compatibility, in constrained and full-featured environments alike.
    Likewise, we saw that the additional community engagement of a BoF was able
    to provide new insights into the use cases and requirements for a LAKE [0],
    both in the OSCORE and the more general case -- this is a great indication
    of the value provided by the broad and cross-area IETF review process.
    
    Based on the input received and energy in the room, we feel that it’s
    appropriate to charter a WG to finish coalescing the requirements for the
    OSCORE use case and evaluate solutions.  From we’ve seen so far, EDHOC
    seems like the leading contender, especially with respect to the “reuse of
    COSE algorithms” proposed requirement, but we of course welcome further
    data (such as on the relative code footprint of core cryptographic
    primitives vs. protocol integration for COSE/cTLS/etc.).
    
    We also feel that it’s appropriate to find a home for work on cTLS to come
    to fruition.  As noted during the BoF, this presents a multifaceted
    problem, with input needed from TLS experts as to which parts of the
    protocol are legacy artifacts vs. cryptographically necessary, and also
    with input needed from domain experts on constrained devices as to which
    protocol features are necessary and where to fall on the spectrum of
    tradeoffs between fully general/full-featured and a stripped-down,
    bare-bones feature set.  On the balance, though, it seems that discussion
    of a general-purpose-but-compact TLS would be most effectively done in the
    TLS WG with additional input and collaboration as needed.  We plan to ask
    the TLS WG if there is interest in rechartering to take on this
    “constrained TLS” work item (and we note that this includes thinking about
    whether it is best done as a standalone specification or a “patch” or
    “filter” to stock TLS that could apply to multiple TLS versions).
    
    For the sake of facilitating discussion, we include draft charter text for
    the OSCORE case, modified based on input from the BoF from the version that
    was previously sent to secdispatch@ietf:
    
    ==[ CHARTER ]==
    Problem
    
    Constrained environments using OSCORE in network environments such as
    NB-IoT, 6TiSCH, and LoRaWAN need a ‘lightweight’ authenticated key
    exchange (LAKE) that enables forward security.  'Lightweight' refers to:
    
      * resource consumption, measured by bytes on the wire, wall-clock time to
        complete, or power consumption
      * the amount of new code required on end systems which already have an
        OSCORE stack
    
    Goals
    
    This working group is intended to be a narrowly focused activity
    intended to produce at most one LAKE for OSCORE usage and close.
    
    The working group will collaborate and coordinate with other IETF WGs
    such as ACE, CORE, 6TISCH, and LPWAN to understand and validate the
    requirements and solution.  The WG will also evaluate work from
    the TLS WG and derivatives thereof, and draft-selander-ace-cose-ecdhe.
    
    Program of Work
    
    The deliverables of this WG are:
    
    1. Design requirements of the lightweight authenticated key exchange
    protocol for OSCORE (this draft will not be published as an RFC but will be
    used to drive WG consensus on the deliverable (2)
    
    2. Specify a lightweight authenticated key exchange protocol suitable for
    use in constrained environments using OSCORE
    ==[ CHARTER ]==
    
    Thanks,
    
    Ben and Roman
    
    [0]  For example, the total number of key exchange operations expected to
    be performed over the lifetime of the device, as might be compared against
    the total lifetime energy budget; and a request to make explicit what had
    previously been implicit assumptions about the cost of various operations
    (on various axes).
    
    -- 
    Lake mailing list
    Lake@ietf.org
    https://www.ietf.org/mailman/listinfo/lake