Re: [TLS] What is the TLS WG plan for quantum-resistant algorithms?

[Thom Wiggers <[e-mail]>]

Hi,

I remembered that this discussion was somewhat summarised in https://datatracker.ietf.org/doc/html/draft-ietf-tls-hybrid-design-03#appendix-B, which might be helpful.

Cheers,

Thom


> Op 9 nov 2023, om 12:00 heeft Scott Fluhrer (sfluhrer) <sfluhrer=[e-mail]> het volgende geschreven:
> 
> We had that argument several IETF’s ago (IETF 105?), and the clear consensus of the working group was that explicit named hybrid combinations (e.g. one for ML-KEM-512 + X25519) was the way to go.
>  
> Do we want to reopen that argument?  Now, I was on the other side (and I still think it would be a better engineering decision, given the right negotiation mechanism), but if it delays actual deployment, I would prefer if we didn’t.
>  
> From: TLS <[e-mail]> On Behalf Of John Mattsson
> Sent: Thursday, November 9, 2023 3:48 AM
> To: Sophie Schmieg <sschmieg=[e-mail]>; [e-mail]
> Subject: Re: [TLS] What is the TLS WG plan for quantum-resistant algorithms?
>  
> Hi,
>  
> Everybody seem to agree that hybrids should be specified. Looking in my crystal ball, I predict that registering hybrids as code points will be a big mess with way too many opinions and registrations similar to the TLS 1.2 cipher suites. The more I think about it, the more I think TLS 1.3 should standardize a generic solution for combining two or more key shares.
>  
> My understanding of what would be needed:
>  
> - New "split_key_PRF" extension indicating that client supports split-key PRF.
>  
> - When "split_key_PRF" is negotiated the server may chose more than one group/key share.
>  
>       struct {
>           NamedGroup selected_groups<0..2^16-1>;
>       } KeyShareHelloRetryRequest;
>  
>      struct {
>           KeyShareEntry server_shares<0..2^16-1>;
>       } KeyShareServerHello;
>  
> - When "split_key_PRF" is negotiated HKDF-Expand(Secret, HkdfLabel, Length) is replaced by a split-key PRF(Secret1, Secret2, ... , HkdfLabel, Length)
>  
> I think the current structure that the TLS server makes the decisions on “groups” and “key shares” should be kept.
>  
> There was a short discussion earlier on the list
> https://mailarchive.ietf.org/arch/msg/tls/Z-s8A0gZsRudZ9hW4VoCsNI9YUU/
>  
>  
> Sophie Schmieg [e-mail] <mailto:[e-mail]> wrote:
> ”Our stated intention is to move to Kyber once NIST releases the standard”
> “I do not think it makes a lot of sense to have multiple schemes based on structured lattices in TLS, and Kyber is in my opinion the superior algorithm.”
>  
> I agree with that. 
>  
> Cheers,
> John Preuß Mattsson
>  
>  
>  
> From: TLS <[e-mail] <mailto:[e-mail]>> on behalf of Sophie Schmieg <sschmieg=[e-mail] <mailto:sschmieg=[e-mail]>>
> Date: Thursday, 9 November 2023 at 08:40
> To: [e-mail] <mailto:[e-mail]> <[e-mail] <mailto:[e-mail]>>
> Subject: Re: [TLS] What is the TLS WG plan for quantum-resistant algorithms?
> 
> > > On 8 Nov 2023, at 8:34, Loganaden Velvindron <[e-mail] <mailto:[e-mail]>> wrote:
> > > 
> > > I support moving forward with hybrids as a proactively safe deployment
> > > option. I think that supporting
> > > only Kyber for KEX  is not enough. It would make sense to have more options.
> > > 
> > > Google uses NTRU HRSS internally:
> > > https://cloud.google.com/blog/products/identity-security/why-google-now-uses-post-quantum-cryptography-for-internal-comms <https://protect2.fireeye.com/v1/url?k=31323334-501d5122-313273af-454445555731-906db70ac616716e&q=1&e=19fc7c2a-a02d-472c-b2ec-cc51f454c161&u=https%3A%2F%2Fcloud.google.com%2Fblog%2Fproducts%2Fidentity-security%2Fwhy-google-now-uses-post-quantum-cryptography-for-internal-comms>
> > > 
> > > If Google decides to use this externally, how easy would it be to get
> > > a codepoint for TLS ?
> > As easy as writing it up in a stable document (may or may not be an Internet-draft) and asking IANA for a code point assignment.
> > 
> > It can be done in days, if needed.
> > 
> >  Yoav
> 
> Just to clarify a few things about our internal usage of NTRU-HRSS: This is for historic reasons.
> 
> Our stated intention is to move to Kyber once NIST releases the standard, see e.g. my talk at PQCrypto [1], where I go into some detail on this topic.
> Long story short, we had to choose a candidate well before even NIST's round 3 announcement, and haven't changed since changing a ciphersuite, while relatively straightforward is not free, so we would like to avoid doing it twice in a year.
> The only security consideration that went into the decision for NTRU was that we wanted to use a structured lattice scheme, with NTRU being chosen for non-security related criteria that have since materially changed.
> I do not think it makes a lot of sense to have multiple schemes based on structured lattices in TLS, and Kyber is in my opinion the superior algorithm.
>  
> [1] https://www.youtube.com/watch?v=8PYYM3G7_GY
> 
> 
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