Re: [COSE] tstr values for kty, alg, crv, etc.

[Carsten Bormann <[e-mail]>]

Hi Daisuke,

> On 2021-07-28, at 13:45, AJITOMI Daisuke <[e-mail]> wrote:
> 
> In my opinion, the tstr type for 'kty', 'alg', 'crv' or 'key_ops' is not necessary because I think the major advantage of COSE is its compactness,but I would like to know what you are assuming as the value of tstr.

The registrant gets the choice between a text string and an integer.

https://www.iana.org/assignments/cose/cose.xhtml lists the registration procedures for certain ranges, e.g.:

https://www.iana.org/assignments/cose/cose.xhtml#algorithms

Range 	Registration Procedures 
Strings of length 1	Standards Action With Expert Review
Integer values between -256 and 255	Standards Action With Expert Review
Strings of length 2	Specification Required
Integer values from 256 to 65535	Specification Required
Integer values from -65536 to -257	Specification Required
Strings of length greater than 2	Expert Review
Integer values greater than 65535	Expert Review

So labels the representations of which would be 1+0 and 1+1 bytes long require standards action, 1+2, specification required, and 1+>2, expert review.

It doesn’t look like anyone has felt a need to register a text string label for an algorithm ID yet; there are still quite a few 1+1 (and even a few 1+0!) values available for registration.

I would expect that, until we run out of codepoints, the registration of text labels will remain an occurrence for special circumstances (which means we might not be prepared for text labels when we finally actually need them).

Grüße, Carsten