1. 21-07-0xxx-00-00001 IEEE 802.21 MEDIA INDEPENDENT HANDOVER Title: Security Optimization During Handovers Date Submitted: July, 2007 Presented at IEEE 802.21 session #21, San Francisco Authors or Source(s): Yoshihiro Ohba (Toshiba), Subir Das (Telcordia), Marc Meylemans (Intel), Suman Sharma (Intel), Madjid Nakhjiri (Huawei), Qiaobing Xie (Motorola), Junghoon Jee (ETRI), Soohong Daniel Park (Samsung), Robert Hsieh (Deutsche Telekom), Srinivas Sreemanthula (Nokia), Michael Williams (Nokia), Ajay Rajkumar (Alcatel-Lucent) Abstract: 802.21 Security Study Group proposal

2. 21-07-0xxx-00-00002 IEEE 802.21 presentation release statements This document has been prepared to assist the IEEE 802.21 Working Group. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.21. The contributor is familiar with IEEE patent policy, as outlined in Section 6.3 of the IEEE-SA Standards Board Operations Manual and in Understanding Patent Issues During IEEE Standards Development http://standards.ieee.org/board/pat/guide.html> Section 6.3 of the IEEE-SA Standards Board Operations Manualhttp://standards.ieee.org/guides/opman/sect6.html#6.3 http://standards.ieee.org/board/pat/guide.html

3. 21-07-0xxx-00-00003 802.21 Security Study Group Proposal

4. 21-07-0xxx-00-00004 Current 802.21 WG PAR PAR says: “The purpose is to improve the user experience of mobile devices by facilitating handover between 802 networks whether or not they are of different media types, including both wired and wireless, where handover is not otherwise defined and to make it possible for mobile devices to perform seamless handover where the network environment supports it. These mechanisms may also be useable for handovers between 802 networks and non 802 networks.” IEEE 802.21 WG decided not to address the security aspect of handovers as part of the current project (see 5 Criteria document) Due to lack of a well defined problem space for security

5. 21-07-0xxx-00-00005 Problem Scope Problem 1: Security Signaling Optimization during Handover Problem 2: MIH level security mechanism Related contributions: 21-06-0727-01-0000-Security_StudyGroup_proposal.ppt 21-07-0024-00-0000-Security_Issues_in_Transition.ppt 21-07-0127-00-0000-Hokey_802.21.ppt 21-07-0085-00-0000-mih-security.ppt

6. 21-07-0xxx-00-00006 Problem 1: Security Signaling Optimization during Handovers

7. 21-07-0xxx-00-00007 What is the Problem? Security-related signaling can add significant delays to seamless handover efforts and in many cases service continuity can not be met, in particular, for real-time applications This becomes even more problematic when handovers occur between heterogeneous networks (e.g. inter-technology, inter-administrative domains with single or dual radio scenarios)

8. 21-07-0xxx-00-00008 Usage Scenario 1 Example: A mobile device can make a transition between two different networks within the same administrative domain Transition between two different subnets based on the same media, e.g. 802.11 Transition between two different subnets based on different media, e.g. 802.11 and 802.16 Authenticator1 Authenticator2 WiFi, WiMAX and/or Cellular AAA/EAP server MN WiFi, WiMAX and/or Cellular Subnet 1 Subnet 2 Single Administrative Domain* * An administrative domain is a logical network that is administered by a single authority using its own authentication and authorization mechanisms

9. 21-07-0xxx-00-00009 Potential Solution Approach Key Hierarchy-based Transition Since in the same administrative domain, no intrinsic reason to authenticate again on transition An already established key hierarchy is all that is needed to support transition Re-key is still needed between mobile device and the new point of attachment –New context (e.g., association parameters between mobile device and the new point of attachment) must be bound to the new key

10. 21-07-0xxx-00-000010 Usage Scenario 2 Example: A mobile device can make a transition between two networks deployed by different administrative domains Transition between two administrative domains based on the same media, e.g. 802.11 Transition between two administrative domains based on different media, e.g. 802.11 and 802.16 Authenticator1 Authenticator2 AAA/EAP server WiFi, WiMAX and/or Cellular MN AAA/EAP server Domain1 Domain2 Multiple Administrative Domains

11. 21-07-0xxx-00-000011 Potential Solution Approach Authentication-based Transition Since different administrative domains, in general authentication can not be avoided There is no reason for the new domain to “trust” keys from the old domain, and no reason for mobile device to “trust” the new domain with keys it used with its old domain Some administrative domains may have “roaming agreements” –We can’t always assume appropriate “roaming agreements” that allow key hierarchy based transition across administrative domains

12. 21-07-0xxx-00-000012 What’s Available Today? In principle, the Key Hierarchy-based transition problem is being addressed by IETF HOKEY WG HOKEY is defining a key hierarchy meant to support transitions across subnet boundaries; focus is on transitions within the same administrative domain HOKEY will not define any protocol or mechanism, if required, between Point of Attachments and mobile devices to effect this No standards group seems chartered to work on the Authentication-based transition problem Some variant pre-authentication scheme (e.g., doc 21-06-0727-01) seems like one plausible approach to this problem

13. 21-07-0xxx-00-000013 Proposed Direction for Problem 1 Different 802 (e.g. 11r) and 3G (e.g. UMTS AKA) technologies have addressed (or are addressing) latency caused by L2 security signaling in handovers (fast roaming, pre-auth etc.) but these are focused on intra-technology handover scenarios Needs to be looked at from a wider perspective given that Seamless heterogeneous handovers are becoming a reality (inter-technology and inter-administrative domains with single/dual radio operation) E.g., Wi-Fi - 3G, Wi-Fi – WiMAX Each access technology has its own way of managing the security aspect  A media independent approach to reduce the security latency during handovers seems to be more appropriate

14. 21-07-0xxx-00-000014 Problem 2: MIH Level Security Mechanism

15. 21-07-0xxx-00-000015 What is the Problem? IEEE 802.21 services affects user mobility Service providers need to ensure users receive best user experience and satisfaction Mutual confidence in exchange of MIH services is a necessary requirement Mobile nodes must be confident when Receiving reliable information (IS) from trusted network sources Receiving/sending events/commands only from trusted network nodes Network must be confident that MIH events/commands are in fact originated from the “said” user MIH info/events/commands are delivered to destination reliably (without tampering) Security becomes an essential ingredient for deployment

16. 21-07-0xxx-00-000016 MIH Access Control Network operator may apply subscription policies to the user for customization, e.g. User can only use certain access technologies => can only query about certain access technologies Various roaming plans/info depending on subscription plans Addressed in 21-07-0035-00-0000-AccessControlIEs.ppt MIH access control is not network access control access level control determines whether and how user can access the link resources MIH access control is what the MIH services users can receive Related to MIH security since the policy control is based on authentication

17. 21-07-0xxx-00-000017 Policy Based MIH Services MIH IS/ECS Policy is about customizing service specific to the user, usually derived from subscription relation with the user Network operation policies Roaming considerations etc Policy setup is either online or offline and enforced in MIHF for that user For MIH, policy impacts on a user basis what information is provided what events and commands can be generated or processed Need to verify the authenticity of the MN for policy-based services Mobile Node Policy functions

18. 21-07-0xxx-00-000018 Hijacking/Replay Issues MIH IS/ECS An ongoing session with one MIHF can be hijacked by providing the response or future packets from a different node A certain packet for an event or command can be replayed later to the same node Not having the means to verify the authenticity of the MIHF service provider or not having replay protection can lead to negative effects Bad Guy MIHF Mobile Node

19. 21-07-0xxx-00-000019 Denial of Service MIHF Good Guy Mobile Node MIH events or commands can be originated by spoofing the MIHF node ID A mobile node and a network node MIHF can be spoofed Any event or command can be triggered falsely to negatively affect the mobility somehow Link-Going-Down, Link-Down and Handover-commit Not having the means to verify the authenticity of the MIHF of a MN or service provider can lead to negative effects Bad Guy Mobile Node MIH source same as other Mobile nodes MIHF Good Guy Mobile Node MIH source same as MIHF Bad Guy MIHF

20. 21-07-0xxx-00-000020 Message Modification by 3 rd party Good Guy MIH IS/ECS Bad Guy MIHF Mobile Node Modify the request and/or response Some intermediate node is capable of snooping, altering and forwarding the MIHF packets IE in Information services could be altered in request or response MIH events can be modified e.g. to change threshold values or even event IDs and parameters Handover-candidate response or Handover-commit from MN or network could be modified to affect mobility (packets buffered/rerouted) Not having the means for data protection (integrity and encryption) from the originating MIHF can lead to negative effects

21. 21-07-0xxx-00-000021 Discovery Issues MIHF MIHF discovery may lead to finding MIHF that may not be trustworthy L2 broadcast discovery is a good example, any one can respond that they are MIHF capable Not having the means to verify the authenticity of the MIHF service provider can lead to negative effects Mobile Node Bad Guy MIHF

22. 21-07-0xxx-00-000022 Requirements Need mutual authentication Network needs to authenticate the user to establish the user privileges to provide and process any information Mobile nodes need to authenticate the network to establish the network node is trustworthy Need integrity protection (message authentication) Network needs to ensure that the user who claims to send the events/commands is in fact the actual source Mobile nodes need to ensure that the network node who claims to send the events/commands is, in fact the actual source Can also take care of replay attacks (w/ new transaction numbers) Need replay protection

23. 21-07-0xxx-00-000023 Relation to Transport security MIH should be independent of the underlying transport Transport has no knowledge of MIH semantics Transport is opaque to MIH data, has no way to verify the MIH packet data is authentic MIH can utilize one or more links/transports at the same time E.g. state-1 query in 802.11 and 802.16 while on a serving network Identities used at the two layers for secure associations are different If an end-to-end MIH communication path is split into a sequence of hop-by-hop MIH transports and lose the info about the origination point Transport layer security will accordingly not be present in some cases, or at least not end-to-end

24. 21-07-0xxx-00-000024 Proposed Direction for Problem 2 Define protocol mechanisms for mutual authentication (needed) Integrity protection (needed) Confidentiality (optional) Define related IEs and TLVs When? The sooner, the better Initial recommendations for base specification Least impact to spec, without loss of functionality utilize existing mechanisms from other SDO (e.g. IETF)

25. 21-07-0xxx-00-000025 Study Group Objectives Identify use cases and investigate issues concerning the 2 identified security areas The SG will work on a PAR defining the scope and requirements to cover the security areas as identified that can lead to a security Task Group under 802.21 WG  Make sure that all work identified is within the scope of 802.21 WG and does not attempt to solve a problem that is being worked in other standards forum

26. 21-07-0xxx-00-000026 Q & A?

27. 21-07-0xxx-00-000027 802.21 Security SG Motion Motion to get 802.21 WG approval to form an 802.21 security Study Group in July 2007 to work on a PAR defining the scope and requirements of the two identified security areas Moved by: Seconded by: Yes: No: Abstain: Result: