Re: [core] [Lake] 🔔 Working Group Last Call (WGLC) of draft-ietf-core-oscore-edhoc-06

[Carsten Bormann <[e-mail]>]

On 15. Feb 2023, at 23:25, Christian Amsüss <[e-mail]> wrote:
> 
> * 3.2 step 3: "The first CBOR byte string is the EDHOC message_3

Ah.

We are using the term “byte string” to describe the generic data model data item with that name (using major type 2 and enclosing a sequence of bytes into a single data item).

We are using the term “encoded CBOR data item” to describe the sequence of bytes that results from encoding a CBOR data item (any CBOR data item of course, not just a byte string).

So where the byte string is h’010203’, the encoded CBOR data item encoding that data item is 43010203 hex.
The latter, of course, can be carried in another byte string h’43010203’, which would then be encoded as 4443010203 hex.
So it is really important not to confuse “CBOR byte string” with “encoded CBOR data item”.

(Of course, this distinction applies to any representation format that can carry its own encodings, as in the JSON text 

    “{\”a\”: 1, \”b\”: 2}” 

which is obviously not the same as the JSON text

    {“a”: 1, “b”: 2}

In JSON this kind of embedding is rather expensive and thus done less often, while in CBOR embedding encoded data items in byte strings is a rather natural way to carry certain kinds of information.)

Grüße, Carsten