[Cbor] Re: Illogical handling of CBOR keys

[Carsten Bormann <[e-mail]>]

Hi Anders,

thanks for the detailed feedback.

On 24. Jul 2024, at 21:39, Anders Rundgren <[e-mail]> wrote:
> 
> Related to CDE.
> 
> https://www.rfc-editor.org/rfc/rfc8949#section-5.6
> 
> According to this section 0.0 and -0.0 are equivalent but only when used as keys. 

In CBOR, 0.0 and -0.0 cannot be both used as keys in a single valid map item. 
This reacts to the fact that many map implementations provided by platforms do not provide ways to do this, and requiring a CBOR implementation to provide their own map implementation sounded unreasonable.

> This does not make sense in a high-level encoder/decoder design where keys are just CBOR data items:
> https://cyberphone.github.io/javaapi/org/webpki/cbor/CBORMap.html#set(org.webpki.cbor.CBORObject,org.webpki.cbor.CBORObject)
> Question: does CDE compliance require you to follow this rule?

No, CBOR compliance requires you to follow this rule.
A map with both keys -0.0 and 0.0 is not valid CBOR (we decided to make this compromise as, if it were valid, it wouldn’t be very interoperable).

> According to the same section, JavaScript values 1 and 1.0 are equivalent which either imply numeric reduction or some special handling of keys. 

What you are alluding to here is a statement of fact about JavaScript, not about CBOR.
It alerts the protocol designer to consider that implementations would likely need to do something unnatural (e.g., mapping all integers to Bigint) to support a protocol that relies on the ability to use both integer and floating point values in the same place.

> In the TC 39 proposal,

Do you have a TC 39 link?

> keys are just CBOR data items:
> https://cyberphone.github.io/CBOR.js/doc/#cbor.map.set

(Wrapper objects, as you seem to call them.)
That is certainly one way to handle JavaScript’s number system.
Using encoded CBOR data items (byte strings) as keys in a map can also help.
I’m sure Joe has a few more in mind...

> Since CDE compliance requires integer and floating point values to be separated, I assume that this is not really applicable.

I can’t parse this.  What is “this”?

Grüße, Carsten