Re: [6tisch] Secdir last call review of draft-ietf-6tisch-enrollment-enhanced-beacon-06

[Michael Richardson <[e-mail]>]

<#secure method=pgpmime mode=sign>

Yoav Nir via Datatracker <[e-mail]> wrote:

    > The draft is short and to the point and easy to understand.  The security
    > considerations (and privacy considerations!) sections are well written and
    > cover everything.  I'm just missing one clause.

    > The first paragraph reads:
    > All of the contents of this Information Element are sent in the
    > clear.  The containing Enhanced Beacon is not encrypted.

    > What I'm missing is "...and this is fine because the 6tisch-Join-Info structure
    > contains no sensitive information."

point taken.  How do you feel about this:

# Security Considerations

All of the contents of this Information Element are sent in the clear.
The containing Enhanced Beacon is not encrypted.
This is a restriction in the cryptographic architecture of the TSCH
mechanism.
In order to decrypt or do integrity checking of layer-2 frames in TSCH, the
TSCH Absolute Slot Number (ASN) is needed.
The Enhanced Beacon provides the ASN to new (and long-sleeping) nodes.

The Enhanced Beagon is authenticated at the layer-2 level using 802.15.4
mechanisms using the network-wide keying material.  Nodes which are enrolled
will have the network-wide keying material and can validate the beacon.

Pledges which have not yet enrolled are unable to authenticate the beacons,
and will be forced to temporarily take the contents on trust.
After enrollment, the pledge will be able to return to the beacon and
validate it.

In addition to the enrollment and join information described in this
document, the Enhanced Beacon contains a description of the TSCH schedule to
be used by the transmitter of this packet.
The schedule can provide an attacker with a list of channels and frequencies
on which communication will occur.
Knowledge of this can help an attacker to more efficiently jam
communications, although there is future work being considered to make some
of the schedule less visible.

--
Michael Richardson <[e-mail]>, Sandelman Software Works
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