Re: Key Usage Clarification in PKIX part 1

[Mike Smith <[e-mail]>]

Good comments.  Good also to differentiate between a digital signature vs. certificate-based authentication 

michael

>>> Trevor Freeman <[e-mail]> 04/09/97 05:55AM >>>
Following yesterdays discussion with the SSL people, it would seem clear
that some clarification on the meaning of the key usage types is
required in pkix part 1. 
I cannot see that when SSL performs a series of cryptographic
transformation on some data in order to derive a symmetric algorithm
session key, it is performing a digital signature. You cannot use DSA in
this protocol. 
Also SSL is performing what PKIX part 3 would describe as a direct proof
of possession(POPO), that is they are establishing the binding between
the public and private key pair. If the CA has a policy to ensure a
strong binding between the public key and the user identity, then the
application may also infer a authentication. The certificate consumers
need to understand that if the CA has a weak binding between public key
and identity, then the authentication is weak as any D Duck class 1
certificate would testify. They also need to understand that if the CA
has a policy of issuing certificate with a weak binding between the
public and private key(i.e. does not do a POPO of the key pair, as part
of certificate creation), then when SSL does a POPO, it does not prove
very much.

Dr Trevor Freeman
Senior Consultant
Microsoft Consulting Services
Microsoft Ltd ECU
> Tel: UK([phone] 
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