Re: [Cfrg] Question from JOSE working group

I would also note that when PKCS#7 was designed, the hash algorithm was
always protected independent the presence of signed attributes.  Either the
hash algorithm was in the signed attributes or it was in the RSA signature
block encoding.   It was only with the introduction of other algorithms that
this was no longer true.

Jim

> -----Original Message-----
> From: cfrg-bounces@irtf.org [mailto:cfrg-bounces@irtf.org] On Behalf Of
> Russ Housley
> Sent: Tuesday, July 03, 2012 8:02 AM
> To: Richard L.Barnes
> Cc: cfrg@irtf.org; jose@ietf.org
> Subject: Re: [Cfrg] Question from JOSE working group
> 
> 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
> 
> _______________________________________________
> Cfrg mailing list
> Cfrg@irtf.org
> http://www.irtf.org/mailman/listinfo/cfrg