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

[AJITOMI Daisuke <[e-mail]>]

Hi Carsten,

Thanks for your quick reply.

> Strings of length 1 Standards Action With Expert Review
> Strings of length 2 Specification Required
> Strings of length greater than 2 Expert Review

I overlooked the above part of the IANA registry.
As for alg, my question was solved and I understood that tstr type values
are not the aliases of int type values but I doubt the necessity to support
tstr type values for alg, etc.
For a specific length value, the number of tstr-type values is much smaller
than that of int type values and I think the merit of introducing the tstr
type is relatively small (compared to the demerit of that).

> (which means we might not be prepared for text labels when we finally
actually need them).

At least my implementation supports only 'int' type and I don't know the
implementations which support tstr type alg. Considering the
interoperability, we'd better update the spec from "tstr / int" to "int"...

By the way, are kty, crv and key_ops the same as alg? At least for kty and
crv, there is no mention about text string in the IANA registry like the
above alg.

2021年7月28日(水) 21:47 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
>
>