Multiple signers and changing receipt requests

[Elanor Foley <efoley@xxxxxxxxxxxxx>]

Hello,

 

As I understand CMS rfc2630 and ESS rfc2634, it is possible to create a SignedData with multiple signers (one signedData with multiple signerInfos). Say one of these signers has included a ReceiptRequest in his signedAttributes. How would another (subsequent) signer also add a ReceiptRequest or modify the existing one? It looks like there is no provision for this. The first signer to request a receipt pre-empts any other signer who may wish a different receipt request. The receipt request itself cannot be modified because it is a signed attribute. Can subsequent signers pretend to be an MLAgent and add a mlReceiptPolicy?

 

Also, I find myself confused by statements in sections 2.2.1 and 2.3 from the ESS rfc. These are highlighted by asterisks below

ESS 2.1 Signed Receipt Concepts

   The originator of a message may request a signed receipt from the
   message's recipients.

 

ESS 2.2 Receipt Request Creation

   <snip>

Only one receiptRequest attribute can be included in the
   signedAttributes of a SignerInfo.


ESS 2.2.1 Multiple Receipt Requests

   There can be multiple SignerInfos within a SignedData object, and
   each SignerInfo may include signedAttributes. Therefore, a single
   SignedData object may include multiple SignerInfos, each SignerInfo
   having a receiptRequest attribute. For example, an originator can
   send a signed message with two SignerInfos, one containing a DSS
   signature, the other containing an RSA signature.

   Each recipient SHOULD return only one signed receipt.

   /***Not all of the SignerInfos need to include receipt requests, but in
   all of the SignerInfos that do contain receipt requests, the receipt
   requests MUST be identical.***/

 

 

But

 

ESS 2.3 Receipt Request Processing

   A receiptRequest is associated only with the SignerInfo object to
   which the receipt request attribute is directly attached. Receiving
   software SHOULD examine the signedAttributes field of each of the
   SignerInfos for which it verifies a signature in the innermost
   signedData object to determine if a receipt is requested. /***This may
   result in the receiving agent processing multiple receiptRequest
   attributes included in a single SignedData object, such as requests
   made from different people who signed the object in parallel.***/

The "different people" are not making different requests? They're just copying the first person's receipt request?

 

Thanks for your help,

 -    Lnr

____________________________________________
Lnr Foley 
Baltimore Technologies
Web: http://www.baltimore.com
_____________________________________________