Re: [Cfrg] Postquantum cryptography in IETF protocols

["Tams, Benjamin" <[e-mail]>]

Hi John,

> Good that CFRG starts some more detailed discussion on PQC. It makes sense
> to support post-quantum key exchange for use cases that need long-term
> confidentiality (15 years). For other use cases I think it can wait until
> PQC key exchange algorithms has been thoroughly evaluated and
> standardized. If implemented now, it should be used in addition to ECDHE,
> just like Google has done with their experimental New Hope implementation.

I absolutely agree with your view on the subject. Especially for those use
cases where the attack scenario "collect today, decrypt tomorrow" is a threat, 
we should start thinking of PQ-safe key exchange methods in time. Even if
they eventually turn out to be insecure; we can now combine them with
classical key exchange algorithms. We have nothing to lose.

There is already IETF work addressing PQ-security in Internet protocols, e.g.
IKE and an Internet Draft for a Quantum-Safe Hybrid Ciphersuite for TLS

https://tools.ietf.org/html/draft-fluhrer-qr-ikev2-03
https://tools.ietf.org/html/draft-whyte-qsh-tls13-03

On the other hand, there is (to my knowledge) no specification for a PQ-safe
patent-free key exchange algorithm suitable for implementation. In fact, in 
https://tools.ietf.org/html/draft-whyte-qsh-tls13-03
only NTRUEncrypt is specified but is subject to patents.

A possible first step is that CFRG creates an Internet Draft. In fact,
the algorithm New Hope has already been implemented as a plugin for
strongSwan (IPSec implementation for the Linux kernel)

https://github.com/strongswan/strongswan/tree/master/src/libstrongswan/plugins/newhope

So why do we not start with a draft for which the above implementation can 
serve as a reference implementation?

Kind regards,
Benjamin