Sign email with double/multiple smime certificates

Aspose.Email Product Family
1

Hello,
Dim SignedMessage As Email.MailMessage = OrgMailMessage.AttachSignature…
Dim SignedMessage2 As Email.MailMessage = SignedMessage.AttachSignature…

SignedMessage2.Save…

The result will not have both signatures, only the last one, and worst, Windows Live Mail won’t show it:

Message could not be displayed
Windows Live Mail encountered an unexpected problem while displaying this message.

Thanks :slight_smile:

2

Hello,

Let me specify, is it acceptable for a message to have multiple digital signatures?
It seems, in the context of S/MIME, it’s not typical to include multiple signatures in a single email message. Each S/MIME email typically contains one signature applied by the sender’s private key.
I think, it might not provide any additional security benefits beyond what a single signature already offers.
In practice, If there’s a need for multiple signers to sign an email, it’s more common to have each signer send their own signed copy of the email, rather than including multiple signatures within a single message.

1 Like
3

Hello,
Thanks for clarifying, according to the rfcs, multiple signatures in cryptographic message were always in place, at least since 2004 when I recall, I was using an ancient .net framework 2.0 SDK which supported that and is no longer working, its highest hash level of acceptable certificates was Sha1!

So wanted to test some conditions, anyway, even if unsupported, you may want to consider this improvement:
when signing an already signed message, the saved result will not open in Microsoft Windows Live Mail (and some others maybe).

4

Thanks for the info, we’ll check it out.

5

Hello, is this feature analyzed or added yet?

6

@ariamehr ,

After analyzing the request, we concluded that support for multiple signatures is not appropriate within the free support scope.

While multiple signatures can be beneficial in specific scenarios, they are not commonly used in typical email workflows. Adding additional signatures does not significantly enhance security unless required for certain processes.

Besides, multiple signatures aren’t a standard practice and may lead to compatibility issues with email clients. Some email clients and libraries may not fully support or correctly process multiple signatures.