[security] Nonrepudiation, and Trusting OpenID Providers

[Shearer, Charles Dylan]

I have some concerns about OpenID, and I would like to see what those
involved think about them.

It seems to me that, regardless of how OpenID is deployed, it is always
possible for an OpenID provider itself to authenticate with a relying party
as any user by forging a request to authenticate using the user¹s
identifier.  This is because a relying party cannot tell the difference
between a user attempting to log in using his or her identifier, and the
user¹s OpenID provider spoofing that user to gain access to whatever
services the relying party provides to that user.  This seems to require
that both users and relying parties put a lot of trust in OpenID providers:
for example, if I used my OpenID identifier for online banking and email, my
OpenID provider could easily access my email and bank account.

Additionally, even if we assume that OpenID providers will not log into
users¹ accounts, I still cannot see how OpenID could provide nonrepudiation
regarding messages sent to a relying party by an authenticated user: for
example, if I authenticate with my bank using my OpenID identifier and then
use the bank¹s ³bill pay² service to pay a bill, there¹s no way the bank can
prove that I ordered that payment because it is possible that someone
working for my OpenID provider logged in as me and ordered it.

Does anyone disagree with my analysis?

Dylan
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