Subject: Re: Dual-signed certificates

From: [email-masked]
Date: Sun, 23 Jul 2000 11:57:31 -0400

Responses below.  I don't think parallel signatures from the CA and
the user are a very good idea, but the user's enveloping signature might be
another matter.

          Tom Gindin

Ben Laurie <[email-masked]> on 07/22/2000 11:39:24 AM

To:   Tom Gindin/Watson/IBM@IBMUS
cc:   [email-masked], [email-masked], [email-masked]
Subject:  Re: Dual-signed certificates

[email-masked] wrote:
>
>      Although a certificate with these exact characteristics might not be
> feasible, how about a CMS SignedData containing the certificate with an
> signedAttribute called "CertificateAccepted" with value GeneralizedTime?
> The other alternative would be a self-signed certificate with an
> "ExternalCertificate" extension, with a value containing the certificate.
> Of course, all these prove is that whoever has the private key agrees
that
> the certificate is valid - they don't do anything to prove who it is who
> has the private key.

Absolutely, but please don't let's get into the whole identity
discussion again. All I care about is the private key.

[Tom Gindin] I was just pointing out the limitation.  I don't want to start
another round of that debate - NR is enough.

>      Getting the acceptance itself into the ordinary certificate would
not
> be feasible.

Why not?

[Tom Gindin] Because an acceptance signature comes after the issuer
signature, or else it doesn't cover the issuer signature.  In any case, the
current signature format is not designed for dual simultaneous signatures.

>      However, do people think it appropriate for the real external
> certificate to be carried around inside a CMS SignedData or a self-signed
> certificate?  It certainly can be done, but should it?

The certificate should be extended to carry two signatures, IMO.

Cheers,

Ben.

--
http://www.apache-ssl.org/ben.html

Coming to ApacheCon Europe 2000? http://apachecon.com/

---

From: Ben Laurie <[email-masked]>
Date: Mon, 24 Jul 2000 10:38:37 +0100

> the user are a very good idea, but the user's enveloping signature might be

Agreed, now I've thought about it some more.

> current signature format is not designed for dual simultaneous signatures.

Right - I was assuming an updated certificate format!

Cheers,

Ben.