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Re: signedattributes in countersignature

2006-05-30 23:45:00

But RFC says:
    The countersignature attribute type specifies one or more signatures
    on the contents octets of the signature OCTET STRING in a SignerInfo
    value of the signed-data.  That is, the message digest is computed
    over the octets comprising the value of the OCTET STRING, neither the
    tag nor length octets are included.

 You say, there is no difference in the input if CounterSignature has
signed attributes. According to the RFC; if exists, input to the Message
digest attribute is the signature value of the SignerInfo.
 I could not find anything in RFC or any other documents this explanation.

 Işıl

It is a SignerInfo, so the normal processing order applies.  The
attributes must be DER encoded before they are hashed.

Russ


At 02:58 PM 5/30/2006, 
ihasircioglu(_at_)uekae(_dot_)tubitak(_dot_)gov(_dot_)tr wrote:
 Yes, I have seen the section. But there is no additional information
about other attribute restrictions and more importantly the input to the
signing process if there are signed attributes in the structure.


Did you see section 11.4 in RFC 3852?  It seems to answer most of
your questions.

The countersignature cannot include the content-type attribute.

Russ

At 04:57 AM 5/29/2006, 
ihasircioglu(_at_)uekae(_dot_)tubitak(_dot_)gov(_dot_)tr wrote:

 Hi,
 My question is about cms structure which has a countersignature
attribute
in its SignerInfos. When countersignature attribute which is again a
SignerInfo, has signedattribute(s), what will be data to be signed?
RFC
3852(Cryptographic Message Syntax (CMS)) only says that:
   The countersignature attribute type specifies one or more
signatures
   on the contents octets of the signature OCTET STRING in a
SignerInfo
   value of the signed-data.  That is, the message digest is computed
   over the octets comprising the value of the OCTET STRING, neither
the
   tag nor length octets are included.

But I could not find any information about countersignature which has
signedattribute? Is it necessary to sign der encoding of the
signedattributes as a usual SignerInfo in the signature structure as
defined in RFC 3852?
   The result of the message digest calculation process depends on
   whether the signedAttrs field is present.  When the field is
absent,
   the result is just the message digest of the content as described
above.      When the field is present, however, the result is the
message
   digest of the complete DER encoding of the SignedAttrs value
   contained in the signedAttrs field.

  Moreover, is there any restriction in signed attributes which may
be
in
countersignature attribute?

 Işıl







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