Subject: RE: RFC 3280 : key usage extension

From: "David Cross" <[email-masked]>
Date: Thu, 5 Dec 2002 15:38:11 -0800

Geoff:

Your assumption is correct.  Most SCEP implementations probably or
should have an RA certificate as an intermediaery that contains key
encipherment for the encryption.

David B. Cross

-----Original Message-----
From: Geoff Elgey [mailto:[email-masked]] 
Sent: Wednesday, December 04, 2002 8:28 PM
To: [email-masked]
Subject: Re: RFC 3280 : key usage extension

G'day,

> You are correct that CA certificates that conform to the profile will
> contain the key usage extension.  However, in the validation algorithm

> we made an attempt to accommodate "legacy" certificates.  This is one
of 
> the cases we support.

Is there a similar accomodation for key usage extension and public keys 
that are used for encrypting?

I'm thinking of SCEP, where a session key must be encrypted with the 
CA's public key, to envelope the enroller's certification request.

RFC 3280, section 4.2.1.3 states that "the keyEncipherment bit is 
asserted when the subject public key is used for key transport. For 
example, when an RSA key is to be used for key management, then this bit

is set."

I'm assuming that encrypting a session key is consistent with key 
transport as defined in section 4.2.1.3.

But all SCEP servers I have come examined return a CA certificate with a

key usage that indicates signing only, not encrypting.

So am I wrong to assume that the keyEncipherment bit should be set in 
the keyUsage extension for CA cert returned from a SCEP server? Or is 
the keyEncipherment bit typically ignored when enveloping?

Cheers,
Geoff