Re: [CFRG] Does OPRF/OPAQUE require full implementation of RFC 9380

[Michael StJohns <[e-mail]>]

On 3/30/2024 8:36 AM, stef wrote:
> On Sat, Mar 30, 2024 at 12:56:10PM +0100, Stefan Santesson wrote:
>> Note that there are not even a "MUST" expressed here. Just a "must" and
>> therefore not a requirement according to section 1.1.
> nothing really is a must, but if you don't implement the hashtogroup as per
> the rfc you will not be able to satisfy the test vectors, and if you don't
> satisfy the test vectors it is difficult to claim compliance with the rfc. and
> also compatibility with all the other implementations. if that is ok with you,
> you should be doing whatever you want.

With an apology here in that CFRG is not supposed to be doing standards, 
and as such mostly can ignore the normal requirements language of 
MUST/REQUIRED, SHOULD/RECOMMENDED, MAY/ALLOWED:

I can't tell from your reply whether or not you mean "MUST" or 
"SHOULD".  The "if you don't do this, you're not compliant with the RFC" 
is pretty much the definition of "MUST".

But "we recommend you do it this way, and if you don't you will not be 
able to satisfy the test vectors" is exactly the definition of "SHOULD" 
and you should include the above explanation for what happens if you 
don't implement hashtogroup as per the RFC.

Pick one.  I'd recommend "MUST" based on the "compliance to RFC" comment.

Later, Mike