Last Modified: 2003-01-20
+ Only legitimate group members will have access to current group communication. This includes groups with highly dynamic membership.
+ Legitimate group members will be able to authenticate the source and contents of the group communication. This includes cases where group members do not trust each other.
An additional goal of the standard will be to protect against denial-of-service attacks, whenever possible.
Due to the large number of one-to-many multicast applications and the sometimes conflicting requirements these applications exhibit, it is believed that a single protocol will be unable to meet the requirements of all applications. Therefore, the WG will first specify a general framework that includes a number of "functional building blocks". Each such building block will be instantiated by one or more protocols that will be interchangable. The functional building blocks and protocols developed at the SMUG Rsearch Group of the IRTF will be used as the starting point for the work of MSEC. Specifically, the following functional building-blocks will be the basis of the standard:
(BB1) Data security transforms functional building block. This building block provide for group and source authentication and group secrecy, assuming that the parties hold the necessary cryptographic keys. This BB will support both IP-layer and transport/application layer security services.
(BB2) Group key management and group security association (GSA) functional building block. This building block makes sure that the group members have the cryptographic keys needed for BB1. This includes secure generation, distribution, and update of the cryptographic keys.
(BB3) Group policy management functional building block. This building block provides means for determination and disemination of group security policy, that governs the behavior of BB1 and BB2. (It is stressed that MSEC will not address general policy management issues, and will concentrate on mechanisms required for BB1 and BB2.)
MSEC will work closely with the Secure Multicast (SMUG) and Reliable Multicast (RMRG), IRTF research groups, and with the Multicast Transport (RMT), IP Security (IPsec) and Policy (Policy Framework and IPSP) WGs of the IETF.
MSEC will generate the at least the following documents:
1 An informational RFC describing the security requirements and problem-space for group and multicast security for one-to-many communications.
This RFC will be based on draft-irtf-smug-taxonomy-01.txt.
2 An informational RFC that specifies the overall framework for the solution. This includes specifying the general functionality of the building blocks and their inter-relations.
This RFC will be based on draft-irtf-smug-framework-01.txt.
3 RFCs detailing the structure and functionality of each building block.
These RFCs will be based on:
4 Standards-track RFCs describing specific protocols that instantiate each one of the functional building blocks. At least one protocol for instantiating each building block will be standardized.
Some of these RFCs will be based on:
|APR 01||Initial Drafts on requirements and problems space, and framework (items 1 and 2 above)|
|JUN 01||Submit requirements and problems space, and framework drafts for publication as Informational RFC.|
|JUL 01||Initial drafts on the functional building blocks (item 3 above).|
|AUG 01||IETF-51: Review building-block drafts|
|NOV 01||Initial Drafts on protocols for instantiating the functional building blocks (item 4 above).|
|DEC 01||IETF-52: Presentation of protocol drafts.|
|FEB 02||Complete building-block drafts WG Last-Call and submit as Proposed Standard.|
|MAR 02||Second Review of protocol drafts.|
|JUL 02||Third review of protocol drafts.|
|JUL 02||Third review of protocol drafts.|
|DEC 02||Final review of protocol drafts.|
|DEC 02||Final review of protocol drafts.|
|DEC 02||Complete protocol drafts WG Last-Call and submit as Proposed Standard.|
|DEC 02||WG disband or re-charter for other work items.|
Minutes of MSEC WG Meeting, 56th IETF, 17 March 2003 --------------------------------------------------- 1. Recharter, Thomas: A new charter was posted to the msec list for discussion. Thomas showed the current MSEC I-Ds list. GDOI & MIKEY are in Last Call. Recharter to extend msec life to 2004 to finish work and develop new focus on distributed architectures and many:many multicast. Mar 03 Last Call on GKMARCH with several more following. New focus areas are not on the list or Proposed I-Ds, but Ran thinks that these problems should be issues for each of the present drafts rather than separate drafts. 2. TESLA Update, Adrian: Brief description of TESLA stream, outline of current drafts, and future works on broadcast authentication. Problem is to prevent receiver from impersonating sender in a secure group. Sender precomputes N+1 keys, 0..N, where Kn = HMAC(Kn-1, 1), K0 = K. K is installed securely prior to the session start. The sender creats a chain from the installed key(0) to key(N-1) where key(N-1) is the first key to be revealed in a TESLA packet during the session. The receiver can always verify that a key(n-k) is part of the chain by computing key(n-j), j=k..n, and compute key(N-1) or some intermediate key that the receiver has received and cached. The TESLA I-Ds is draft-ietf-msec-tesla-intro-01 that adds immediate authentication and concurrent TESLA instances (to handle receivers over networks with a wide range of packet delays. draft-ietf-msec-tesla-spec-00 is current technical draft that gives a bootstrapping procedures (e.g. time synchronization), format, operation with ESP, etc. B.Whillock has done a reference implementation that is available on the web. Looking for a second implementation. Also need to integrate with ESP/MESP. 3. IPSEC Multicast Issues, Brian: Ran, Mark, Thomas and Brian wrote an I-D to document the multicast issues in AH/ESP while they are being revised by S.Kent. The issues are (1) SPI allocation and SA lookup using 3-tuple without using source address, (2) Anti-replay protection for multi-sender SAs (part of new charter of msec), and (3) ICV name. Overall, this was a productive exchange IPSEC and MSEC with good collaboration with S.Kent. 4. MESP, Mark: Made MESP into a transform framework for ESP rather than a separate protocol. The framework is based on group secrecy, internal authentication and external authentication where external authentication protects internal. Need to resolve making ENC, INT, EXT processing order to be mandatory. 5. Feedback messages, Lakshminath: Feedback is needed for GSA synchronization, NAKs, and de-registration. Most GKM systems keep a unique key per member; suggest we use that unique key for feedback from each group member. SA lookup could probably use the SPI. Proposed feedback message resembles the groupkey push message in GDOI. Hugh pointed out that the unique key is usually a KEK and said that the use of a KEK for a TEK could be problematic. Replay protection may use the SEQ# and this may work for NAKs and de-registration but not for out of sync feedback messages. Question: is this something the group should do? The answer is yes. 6. Group key management, Lakshminath: Do one RFC for LKH, OFT, and OFC as well as treating key tree management. The latter uses binary or natural number encoding, the goal is to manage the splitting and shrinking in an efficient manner. Zhang et. al. scheme keeps rekey messages small and limits number of messages for maintaining tree. Two Options. First, standardize key tree encoding and try to get a key tree encoding for all interesting trees. Second, GCKS may advertise a standardized scheme and use it - tradeoffs footprint, communication cost, etc. 7. GSAKMP, Hugh: GSAKMP Light done in Sep 2001 that was shorter and simpler. Since GSAKMP Light is favored, we decided to focus just on GSAKMP Light and make it GSAKMP. Old GSAKMP considered for Informational RFCs; Russ favors Experimental over Informational; if it catches on, then an Experimental track protocol can go standards track, Informational cannot. 8. Policy Token, Hugh: New spec has GSAKMP Roles and Policy token. GSAKMP creates set of roles (GO, GCKS, Sub GCKS,and GM). Policy token wraps policy and sent from GO to GCKS who then distributes it to subordinates of group members (GM). GSAKMP protocol incorporates policy-token dissemination. Policy uses Identification, Authorizations, Access Control, Mechanisms, and Signature. Each was explained. 9. DHHMAC for Mikey, Martin: intended for proposed standard, identity protection clarified, aligned with MIKEY v6, and editorial improvements. Document is ready for WG last call? But a -02 version will be submitted prior to last call. Ran said that this probably should not go ahead of MIKEY. Thomas will submit in two weeks. Also, there may be some need for EC for MIKEY. 10. SDP Security Descriptions, Mark: After a brief overview of SDP, Mark described two configurations for which SDP Security Descriptions apply; one is an end-to-end RTSP running in TLS; the other is a hop-by-hop SIP running over some collection of TLS connections. He briefly described the SDP status, syntax, parameters and next steps. In the discussion, Russ went thumbs down on the hop-by-hop SIP security descriptions as offering no security. Mark and Dan Wing wrote the draft-ietf-mmusic-sdescriptions-00.txt and will be updating it to draft-ietf-mmusic-sdescriptions-01.txt in the Spring.