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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) : I. Property
Filename : draft-ietf-smime-multisig-03.txt
Pages : 19
Date : 2007-11-16
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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