Subject: I-D Action:draft-ietf-smime-multisig-04.txt

From: [email-masked]
Date: Tue, 22 Jan 2008 14:50:02 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the S/MIME Mail Security Working Group of the IETF.

	Title           : Multiple Signatures in S/MIME
	Author(s)       : S. Turner, J. Schaad
	Filename        : draft-ietf-smime-multisig-04.txt
	Pages           : 20
	Date            : 2008-01-22

CMS SignedData includes the SignerInfo structure to convey per-signer 
information. SignedData supports multiple signers and multiple 
signature algorithms per-signer with multiple SignerInfo structures. 
If a signer attaches more than one SignerInfo, there are concerns 
that an attacker could perform a downgrade attack by removing the 
SignerInfo(s) with the 'strong' algorithm(s). This document defines 

 the multiple-signatures attribute, its generation rules, and its 
processing rules to allow signers to convey multiple SignerInfo while 
protecting against downgrade attacks. Additionally, this attribute 
may assist during periods of algorithm migration. 

Conventions used in this document 

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 
document are to be interpreted as described in [RFC2119]. 

Discussion 

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