RE: signer authentication

Perhaps the terminology may be somewhat misleading...
Any digital signature cannot offer signer authentication by itself.
Signature can be replayed, be it an XML one or a different format. While
under a PKI one can trace the liability of the signers' identity to a higher
level (or a different person), one may even trust them, however it does not
assure the other party sent you the message in response to you. For that you
need to have nonces in your employ.
Authentication of signer here may mean two things:
1. authentication of a conversation party
2. authentication of origin

The second can be achieved through signatures (e.g. XML sigs). Are we
certain the users will only understand it in this sense and not the first
one?

Ilan Zohar



-----Original Message-----
From: Dournaee, Blake [mailto:bdournaee@rsasecurity.com]
Sent: Monday, June 04, 2001 11:44 PM
To: 'Joseph M. Reagle Jr.'
Cc: 'w3c-ietf-xmldsig@w3.org'
Subject: signer authentication


Joseph,

I am a bit concerned with the use of the term "signer authentication" in the
dsig recommendation. These two
sentences from the dsig (coupled with the definition of "signer
authentication" from the glossary) seem to contradict
each other:

"... XML Signatures provide integrity, message authentication, and/or signer
authentication services for data of any type.."

"The XML Signature is a method of associating a key with referenced data
(octets); it does not normatively
specify how keys are associated with persons or institutions..."


The first sentences says that we support signer authentication and the
second sentences says that we don't. I think it is clear that there is no
way to validate the verification-key-to-person relationship (XML dsig can't
do path validation by itself) using only XML dsig, so I am really wondering
about the definition of "signer authentication services." 

Is it necessary to say that XML dsig supports signer authentication
services? Is this refering to the inclusion of verification material in the
signature itself (such as <KeyInfo>)?

Thanks,

Blake Dournaee

Received on Tuesday, 5 June 2001 11:54:48 UTC