Subject: [AAA-WG]: [Issue] NASREQ: Keying AVPs are insecure

From: Bernard Aboba <[email-masked]>
Date: Sun, 3 Mar 2002 08:21:00 -0800 (PST)

Submitter: Jesse Walker
Submitter email address: [email-masked]
Date first submitted: March 2, 2002
Reference:
Document: NASREQ
Comment type: T
Priority: S
Section: 2.1
Rationale/Explanation of issue:

Diameter keying AVPs cannot securely distribute a key for its intended
purpose. While they may be suitable for handing off a key between the
authentication server and the NAS/Access Point, intended for 
communications between themselves alone, as constituted today they are
insecure for transferring a session key intended for use between the
NAS/AP and the client. To become secure, the key handoff has to be
enhanced to incorporate additional cryptographic state that can be
used to provide assurances to all these parties involved in the
transaction. 

Examples of such state are the information communicated among the KDC and
the communicating parties in the Needham-Schroeder and Otway-Rees
protocols.

Proposed change:

A three-way handshake should be incorporated so that key distribution and
confirmation can be dealt with uniformly across multiple environments.
These key distribution methods require active participation by three
parties instead of two.