Draft IETF S/MIME - Multiple Signatures in S/MIME12.03.2008
Abstract: Zdroj: http://www.ietf.org/internet-drafts/draft-ietf-smime-multisig-05.txt
Cryptographic Message Syntax (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'