Re: [Atlas] Status Update

[Benjamin Kaduk <[e-mail]>]

On Sat, Jun 23, 2018 at 01:19:16AM +0530, Abhijan Bhattacharyya wrote:
> +1 Dan.
> The draft https://tools.ietf.org/html/draft-bhattacharyya-dice-less-on-coap-01 also proposes how the session initiation part of DTLS can be switched to CoAP to optimise the resource usage during session establishment by leveraging the lightweight semantics of CoAP. Also, to accomplish the stated objective of establishing end-to-end security association in a secure manner and managed at the application itself. The draft also tries to be less disruptive to existing DTLS implementations by defining an adaptation layer that ensures channel security by allowing the reuse of the existing DTLS record-layer encryption through the session key tuple from the CoAP layer. Of course there can be several other ways to accomplish this than what has been described in the draft.

There seems to be some "novel crypto" in here; it would be good to build on
standard blocks like Needham-Schroeder (e.g., as realized in Kerberos), to
make sure all the needed key confirmation and freshness properties are
realized.  The best freshness properties tend to occur when one endpoint
proposes a subsession key that must be confirmed by the other, which then
produces its own sub-subsession key that is likewise confirmed by the
original party.  It's best if there is contributory behavior for the keys
as opposed to just encrypting sub-keys in the previous key, though that
does tend to involve more hashing which induces cost.

-Ben