Hi Maik,
On 2022-04-21, at 14:50, Maik Riechert
<[email protected]> wrote:
>
> [COSE_Signature] / [+ COSE_Signature]
>
? 7 => COSE_Signature / [+COSE_Signature] ; Counter signature
actually (no array for a single signature).
This can be disambiguated because the three-element array that a COSE_Signature
is, is never structured such that it can be misunderstood as an array of
COSE_Signatures. In CDDL (following some indirections):
COSE_Signature = [
protected : bstr .cbor header_map / bstr .size 0
unprotected : header_map
signature : bstr
]
So the contents of the array starts with a byte string, then a map follows, and
it finally is a byte string.
Maybe not the finest day of optimizing one’s CBOR, but not hard to implement
either: The value for key 7 always is an array. If the first element of that
is a byte string, process (and validate) the array as a single signature. If
the first element is another array, process (and validate) the outer array as
an array of signatures.
Grüße, Carsten
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