----- Original Message -----
Sent: Wednesday, July 21, 2004 9:12
PM
Subject: [STDS-802-16] [전체회신]
[STDS-802-16] Cleaning up 802.16e security
Hi, DJ and all.
I would like to comment on the approaches of PKMv2 to
upgrade the current PKMv1.
In my opinion, when we upgrade or revise the currently fixed
specifications, we shall provide the backward compatibility to the older
one. Even in the case of backward compatibility cannot be fully supported,
we should clearly resolve the known problems in the current specification by
maximizing the reusability of the current one. But, the PKMv2 overlooked
these issues.
Currently proposed PKMv2 is a new and separate PKM protocol
with PKMv1. The Key hierarchy (C802.16e-188r2) is different with that of
PKMv1 (It is more systematically designed and conceptually better than the
older one, but it is not compatible with that). The Key lengths are
different and the input parameters are different, even if to the same
algorithms:
- PKMv1 AK = 160 bits,
PKMv2 AK = 128 bits;
- PKMv1 & PKMv2 HMAC Key
Derivation Function is different, even though the SHA-1 algorithm is used to
both, and its key length (160 vs. 128) and input parameters too.
And the PKMv2 uses the newly defined AES_Key_Wrap for
transferring keys as mandatory feature for PKMv2 (In session #32, the
AES_Key_Wrap was accepted already. But, I hope it will to be modified to
include the older key transferring mechanisms).
Anyway, we can say the current PKMv2 (and its key hierarchy
(188r2)) is not backward compatible with PKMv1. And it is not fully
supported one of the most important goals and requirements of the
PKMv2 - "It should be backward compatible with the existing PKMv1." (See Ad
Hoc documents: Jeff Mandin, "PKMv2 - Goals and Requirements"; David
Johnston, "A New PKM for 802.16")
As you know, TGe PAR (IEEE
802.16-02/48r4, approved in 2002-12-11, and the only valid one) state that
the following two types of interoperability (or backward compatibility)
should be supported: "Subscriber stations specified herein, within
stationary, shall interoperate with base stations in IEEE Std 802.16a. Base
stations specified herein shall interoperate with stationary subscriber
stations specified in IEEE Std 802.16a." The exact meaning of IEEE Std
802.16a should be interpreted as IEEE Std 802.16-2004.
On the basis of that PAR statement, the TGe-based MSS, when
stationary, shall be interoperable with the TGd-based BSs (supporting PKMv1
only), but the PKMv2 is not backward compatible with PKMv1 so that the
requirements are not fulfilled. And the TGd-based BS shall interoperate with
the TGd-based SS (supporting PKMv1 only), but when the TGe-based BS cannot
provide the PKMv1 capability, the requirements are not satisfied, too.
Therefore, in order to provide the backward compatibility
(and/or interoperability) with TGd, the TGe-based MSSs and BSs shall provide
both of the PKMv1 and PKMv2 capabilities. It is a too much burden and the
duplicated functionality to the MSSs.
Generally speaking, I hope that the PKMv2 should support the
various possibilities of authorization and encryption modes as a superset of
including PKMv1 concepts.
Fortunately, DJ proposed and showed me the modified Key
hierarchy mechanism (188r3) to mitigate our uneasiness by introducing the
HMAC SHA-1 key generation, and modified to change the proposal to allow
EAP-only mode. We have been reviewing the proposal and we would like to
propose an alternative by slightly change the DJ's proposal to maximize the
backward compatible and reusable features with PKMv1. By doing that, we can
reduce the overhead of implementing the two completely different mechanisms
in each Mobile subscriber station, and will get a soft-landing from PKMv1 to
PKMv2.
Sincerely,
Chulsik Yoon,
Senior Engineer,
ETRI
P.S.
I would like to mention the data encryption issue of PKMv2,
not relating to the Key hierarchy issue.
In PKMv2, we have generally agreed on using the AES
algorithm for key management and data encryption. So, in my thought, if we
select the PKMv2 based key management methodology, then we will also use the
AES algorithm (not the DES algorithm) for data encryption. In the current
specification, only the AES-CCM mode can be provided to data encryption
using AES algorithm. Even thought, the AES-CCM can provide the high security
capabilities by using the Counter and Message Integrity Check with AES, it
needs a large amount of overhead (total 12 bytes of overhead per PDU; 4
bytes PN and 8 bytes of Cypertext ICV). In my opinion, most of the user
service needs not this type of highly secure mechanisms, except the monetary
transactions such as internet banking, mobile commerce, etc. Therefore, the
another AES mode (not CCM), not having too much overhead for data encryption
transaction, need to be added to the current security mechanisms in IEEE
802.16 specifications.
Thank You.
원본 내용:
보낸사람:
owner-stds-802-16@listserv.ieee.org[dj.johnston@INTEL.COM]
받는사람: STDS-802-16@listserv.ieee.org
제목:
[STDS-802-16] Cleaning up 802.16e security
받은날짜:
2004/07/17 토 12:15
All,
I think the input to the
security work went rather well. We got most of the underlying mechanisms in
the spec. Compare this with the time it took 802.11i to get to this stage.
Of course we had the benefit of their hindsight.
As some of us discussed in the meeting, there are a few
things to be done with the security work but also there seems to be
agreement that we need to identify and limit the list of things we need to
do, in order to bring the work to a close.
My list of things to be done is as follows:
EAP Key agreement
Generic Management Frame Protection
PKMv2 Key Hierarchy
PKMv2 Security State Machines
Test Vectors (for the crypto algorithms operating
over packets)
Vulnerability
analysis/corrections
General
clean up of the contributions that were accepted (we have LB14c for
that)
I have vague memories of Jeff having another
item for this list but its leaked from my head.
I
will try to coordinate a consensus position on what the key heirarchy should
be. So I'd appreciate comment on it. Particularly from anyone who disliked
the current proposal enough to vote against it. I don't think the discussion
in the meeting shed much light on what the concerns were, since I still
don't know.
EAP Key agreement is in a similar situation. Jeff provided
text, but it didn't pass. Therefore any input on what is needed to make it
pass is welcome.
Anyone who can commit to filling in other parts of the
framework should declare their interest, so people interested in
contributing to the same areas can compare notes.
Hopefully we can reach some sort of consensus before the
next meeting.
Regards,
DJ