dual-use digital signature vulnerabilityastiglic at okiok.com

[Sean W. Smith]

On Jul 19, 2004, at 11:40 AM, Anton Stiglic wrote:

> The X.509 PoP (proof-of-possession) doesn't help things out, since a 
> public
> key certificate is given to a user by the CA only after the user has
> demonstrated to the CA possession of the corresponding private key by
> signing a challenge.  I suspect most implementation use a random 
> challenge.

I would have thought that de facto standard approach is: the client 
constructs the certificate request message, which contains things like 
the public key and identifying info, and signs it.  The CA then checks 
the signature against the public key in the message.

Quickly checking with our deployment folks...this is how it works the 
standard browser/OS suites, with the iPlanet Certificate Management 
System at the CA.    (We combine CA and RA here.)

It would be interesting to see if there's support software out there 
that does something as naive as sign a random challenge.  I really 
suspect this is a strawman...

(Darn it, this is creating the need for some real data: how many X.509 
certs are in use today, how many of these are on standard user 
platforms, what are the keys used for, and how was PoP handled?)

--Sean


---------------------------------------------------------------------
The Cryptography Mailing List
Unsubscribe by sending "unsubscribe cryptography" to majordomo at metzdowd.com