Sender Authentication and the Surreptitious Forwarding Attack in CMS and S/MIME

Document Type Expired Internet-Draft (smime WG)
Author Donald Davis 
Last updated 2001-10-01
Stream Internet Engineering Task Force (IETF)
Expired & archived
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Stream WG state WG Document
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IESG IESG state Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


By default, a CMS signed-and-encrypted document or message authenticates only the document's originator, and not the person who encrypted the document. This subtle limitation exposes CMS and S/MIME signed-and-encrypted data to 'surreptitious forwarding.' Secure-messaging standards have treated surreptitious forwarding as an insoluble problem of user carelessness, and have long accepted the risk of this attack. This document discusses easy cryptographic remedies for this attack, suitable for incorporation into the CMS and S/MIME specifications. This document is an abridgement of [U2001].


Donald Davis (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)