Re: [Cfrg] Question from JOSE working group

[Russ Housley <[e-mail]>]

Richard:

> Actually, the inclusion of the hash algorithm under the signature is optional:
> "
>      signedAttrs is a collection of attributes that are signed.  The
>      field is optional, but it MUST be present if the content type of
>      the EncapsulatedContentInfo value being signed is not id-data.
>      [...]  If the field is present, it MUST
>      contain, at a minimum, the following two attributes:
> 
>         ...
> 
>         A message-digest attribute, having as its value the message
>         digest of the content.  Section 11.2 defines the message-digest
>         attribute.
> "
> 
> Since "id-data" means "no more ASN.1 structure", for JOSE, the content type is effectively always "id-data".

In practice, there are other attributes that one wants signed, such as signing-time, so the algorithm identifier gets included.

Russ