optional fields in time stamp responses.

[Peter Sylvester <Peter.Sylvester@xxxxxxxxxx>]

It seems to me that a lot of fields in a time stamp response
or dcs response can be avoided by using signed/authenticated
attributes. 

For example the time can be replaced by a signing time attribute.

In general I believe that an attribute that contains a cms
document plus a description/pointer would be very useful:

- The responses from TDAs are just signed documents.

- You want to include DCS token cpkc for your signature
  cert and another for possession of data in the signature
  of the data. 

- In an ess three way signed/encrypted/signed structure, one
  might add a dcs validation response for the encryption
  cert to indicate that the recipients dcs server 'authorisation'
  to use the encryption key. 

Otherwise each application protocol like time stamping or dcs can 
define its own oid (which would be necessary anyway for oscp
responses).

Thoughts?
PS