Subject: [Nea] NEA PT MitM attack and countermeasure

From: Stephen Hanna <[email-masked]>
Date: Fri, 19 Mar 2010 23:31:40 -0400

NEA-WG participants,

Paul Sangster and I took an Action Item from the
January 28, 2010 NEA-WG Virtual Interim Meeting
to send a description of the Man-in-the-Middle
attack addressed by the D-H PN mechanism in
PT-EAP and the manner in which D-H PN addresses
this attack. We're finally done with this.

As agreed on the call, graphics really help to
describe the attack and the countermeasure.
Therefore, we have created two documents with
graphics to explain. Here they are.

We recommend that you start by reading the
document titled "Preventing Asokan Attacks
with Cryptographic Bindings". This explains
the attacks and countermeasures to a first
level of detail. If you want to know details
of how the Trusted Platform Module (TPM) is
used in this environment, read the other
document. And if that's not enough, you can
always read the TCG specifications referred
to in the TPM document.

Paul and I will do a presentation about this
at the NEA WG meeting on Monday.

I apologize for taking so long to complete
this action item. I'm afraid that we (like
everyone) are very busy so things often get
pushed to the final deadline.

Thanks,

Steve

---

From: Stephen Hanna <[email-masked]>
Date: Sun, 21 Mar 2010 06:56:25 -0400

I've been asked to provide a bit more context for my email.
Good idea.

The Asokan attack described in the attachments to my email
relates to any security protocol that runs inside a tunnel.
I won't attempt to describe the whole attack here. The Asokan
paper attached to my email does that much better. Suffice it
to say that the best solution for the Asokan attack is for
the server to ensure that the inner protocol and the tunnel
terminate on the same device.

The Asokan attack applies to both PT proposals received by
the NEA WG: PT-EAP and EAP-NEA-TLV. PT-EAP includes a
countermeasure called Diffie-Hellman Pre-Negotiation (D-H PN)
that defeats the Asokan attack. EAP-NEA-TLV does not include
any countermeasure for the Asokan attack.

During the NEA Interim Virtual Meeting in January 2010, several
people complained that they didn't understand the Asokan attack
and the D-H PN countermeasure. Paul and I volunteered to write
an explanatory document. That's the document that I attached to
my last email.

We will discuss this issue further in the NEA WG meeting this
Monday at IETF 77 (1300-1500 PDT). I look forward to seeing you
there. If you can't attend the NEA WG meeting, feel free to
review the documents and comment on the NEA WG email list.

I hope this context is useful.

Thanks,

Steve

-----Original Message-----
From: Stephen Hanna 
Sent: Friday, March 19, 2010 11:11 PM
To: [email-masked]'
Subject: NEA PT MitM attack and countermeasure

NEA-WG participants,

Thanks,

Steve