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Re: Straw Poll: encoding of authenticated attributes in cms-auth-enveloped ID

2007-03-28 03:58:18

"Turner, Sean P." <turners(_at_)ieca(_dot_)com> writes:

There was one open issue (the last slide) that dealt with the encoding of
authenticated attributes.  It was discussed at the meeting; however,
responses from a wider audience (i.e., this list) is necessary.  Please
indicate your preference on whether:

A) The encoding of the authenticated attributes should be done exactly the
same as in SignedData.

B) The encoding of the authenticated attributes should use the encoding that
will be transmitted.

I've already talked to Russ about this in private a while back, I'd strongly
support a move to SEQUENCE OF and bits-on-the-wire encoding:

-- Snip --

There is one other change that would *really* help implementors (and that
should have been made ages ago for any new format that includes
auth.attributes), change the:

  attributes [0] SET OF Attribute

to:

  attributes SEQUENCE OF Attribute

The former is a royal pain for implementors because what's transmitted isn't
what's hashed, and the DER rules for sorting SET OF elements is an eternal
booby-trap for implementors (the CMS spec should really include big red
flashing lights and klaxons in the appropriate section warning people about
this).  With this change, a large chunk of the text necessary in "Message
Digest Calculation Process" simply falls away, because now you can just hash
the bits-on-the-wire form rather than having to rewrite the data first.

-- Snip --

Peter.