[Cryptography] What is the format to add multiple signatures (Would PKCS#7 work?)

[Alfonso De Gregorio]

On Sat, Jul 25, 2015 at 6:02 PM, Puneet Bakshi <bakshi.puneet at gmail.com> wrote:
> Hi,
>
> I want to add multiple signatures to a document. Which PKCS standard can be
> used? Can PKCS#7 signature has the capability to add multiple signatures to
> a document?
>
> Regards,
> ~Puneet

With CMS / PKCS#7 multiple signatures can be applied to a message.

For example, CMS / PKCS #7 allows multiple entities to each sign the
same message (i.e., multiple signers use-case). The same standard
allows also the same entity to sign the message using multiple
signature algorithms. This helps to prevent downgrade attacks and may
assist algorithm migration (i.e., multiple signature algorithms per
signer use-case). You may want to review RFC 5752
https://tools.ietf.org/html/rfc5752

-- Alfonso