[dss] Authentication in DSS

["Kaliski, Burt" <BKaliski@rsasecurity.com>]

At the January 13 teleconference, I raised the question of how requesters
will be authenticated to a DSS service.

In some digital signature policies, authentication steps occur at two
levels, initially to establish the valid identity corresponding to the
signer's session and subsequently for individual digital signatures that are
to be applied. In a smart card environment, this corresponds to the policy
where a second PIN is required to approve a digital signature.

If the DSS service relies on an authentication authority (e.g., SAML), the
two-authentication policy could be achieved via two separate
authentications. Alternatively, the DSS service could manage its own
authentication (e.g., accept a PIN) in addition to a SAML assertion from an
authentication authority.

Key-splitting raises interesting authentication requirements. If the DSS
service cryptographically splits its signing key between two servers, then
each server needs assurance that the user has been authenticated. If both
servers rely on a single authentication authority, however, then compromise
of the authentication authority would undermine the benefits of
key-splitting.

I'd be interested in hearing the group's suggestions on these authentication
issues.

-- Burt Kaliski
RSA Laboratories