Re: [MLS] Stupidest possible message protection

As I said earlier:

> I think that for the sake of simplicity clients should choose whether to encrypt HS messages or not right at group creation (and prevent downgrade attacks by committing to extra state in the group state, just as mentioned). We can always explore later how we would handle “HS message protection agility”, if this turns out to be necessary.

In other words, HS encryption should be fixed for now. Possibly even forever, unless we come to the conclusion it’s a bad idea.

> On 3 Dec 2018, at 22:38, Richard Barnes <rlb@ipv.sx> wrote:
> 
> Do you also mean that all the clients in a group decide independently?  (Even with a single vendor, you could have version migrations). Or does the group need to agree?
> 
> On Mon, Dec 3, 2018, 16:37 Raphael Robert <raphael=40wire.com@dmarc.ietf.org <mailto:40wire.com@dmarc.ietf.org> wrote:
> 
> 
>> On 3 Dec 2018, at 22:27, Katriel Cohn-Gordon <me@katriel.co.uk <mailto:me@katriel.co.uk>> wrote:
>> 
>> I think "clients choose" != "users choose" --- rather, whoever builds this into their application makes the choice for their users in the client code.
> 
> That’s what I meant. It will be up to the application vendor to decide on the UX.
> 
>> 
>> 
>> On Mon, 3 Dec 2018, at 9:10 PM, Russ Housley wrote:
>>> 
>>> 
>>>> On Dec 3, 2018, at 10:46 AM, Raphael Robert <raphael=40wire.com@dmarc.ietf.org <mailto:raphael=40wire.com@dmarc.ietf.org>> wrote:
>>>> 
>>>> I agree with Richard that letting clients choose is a good idea. I think that for the sake of simplicity clients should choose whether to encrypt HS messages or not right at group creation
>>> 
>>> 
>>> It is not clear to me how a user would make that choice.  They do not really have much visibility into the consequences of the choice.  So, it would be good for this group to make to choice or provide a concise description of those consequences in language a user might find helpful.
>>> 
>>> Russ
>>> 
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