802.16e

1. 802.16e Vijay Chauhan Srinivas Inguva

2. 802.16 Overview • Basic Idea: Metropolitan area wireless broadband service. • Main roles involved in 802.16: • Base Station (BS) • Mobile Station (MS) / Subscriber Station (SS) • Two security protocols of interest: • Authentication/Authorization protocol • Traffic Encryption Key (TEK) Management

3. Authentication Protocol • Goals: • Authentication using X.509 certificates and/or EAP • Establish a shared secret, called the Authorization Key (AK) • AK is used to generate various other keys • Structure of a certificate based Authentication exchange: MS → BS: Cert(Manufacturer(MS)) MS → BS: Cert(MS), Capabilities, SAID BS → MS: {AK}Kms, Lifetime, SeqNum, SAIDList

4. TEK Management • After initial authentication, BS initiates a 3-way handshake to transfer TEKs to MS • TEKs generated by BS • Have a specified lifetime, after which new TEK is requested by MS • Structure of the 3-way handshake: Challenge: BS → MS: NBS, SeqNum, AKID, HMAC/CMAC Request: MS → BS: NBS,NMS, SeqNum, AKID, Capabilities, Parameters, Settings, HMAC/CMAC Response: MS → BS: NBS,NMS, SeqNum, AKID, SAID, E_KEK{TEK}, Parameters, HMAC/CMAC

5. Vulnerabilties • Similar Security architecture to 802.11i • Vulnerable to similar DoS attacks?

6. CS 259 MOBIKE Summary Faisal Memon Erik Weathers

7. MOBIKE • IKEv2 Mobility and Multihoming Protocol • As defined in draft-ietf-mobike-protocol-07.txt • Main purpose • For roaming devices (devices which move and hence have changing IP addresses), that want to keep the existing IKE and IPsec SAs in place despite the IP address changing, and without requiring a full rekey. • Secondary purpose • Multihomed (multiple interface) device which decides to change its IKE endpoint IP. Could be a result of link failure or other conditions.

8. MOBIKE Init Exchange KEi, Ni KEr, Nr I R {IDi, MOBIKE}KIR {IDr, MOBIKE}KIR Typical IKEv2 init exchange, with notify declaring support for MOBIKE.

9. MOBIKE Address Change Exchange {UpdateSA_Address}KIR {ACK}KIR I2 R {Cookie}KIR {Cookie}KIR Initiator IP address changed to I2. Cookie exchange is for optional return routability verification.

10. Scott’s Protocol Scott Lulovics

11. Scott's Password-based Protocol • “Efficient Short-Password key exchange and Log-in Protocols” - Michael Scott, September 2001 • Based on the Diffie-Hellman key exchange and El Gamal public key encryption algorithms • Faster than existing techniques (the password is short)

12. Efficient-Short-Password Key-Exchange (ESP-KE) protocol • Global values • p – prime number • q – prime divisor • α and β – unrelated generators of the prime order sub-group of order q • Password P known to Alice and Bob. (P << q) • Alice and Bob choose random numbers a and b, respectively, such that 1≤ a,b < q.

13. B = αb mod p ← B If A = 0:Abort k = (A ·βP)b mod p Mb = H(0, k, P) ← Mb If H(1, k, P) ≠ Ma: Abort ESP-KE A = αa / βP mod p A → k = Ba mod p If H(0, k, P) ≠ Mb: Abort Ma = H(1, k, P) Ma →

14. CS 259 Slicing the Onion: Anonymous Routing without PKI http://nms.lcs.mit.edu/~sachin/slicing.html Saurabh Shrivastava

15. Bob Na Nb Nd Nc Alice What is Onion Routing - packets are encrypted in layers - each node decrypts the packet using its key, figures out the next hop - usually public/private key pairs used, but here symmetric keys will be used - how to distribute the keys to nodes? use information slicing: split the key into lots of pieces, send them on disjoint paths to the respective target nodes

16. Anonymity • Degree of Anonymity • Measured as entropy of the system • Unlinkability • … of different actions by a single user • Source/Destination anonymity • Source is hidden from all nodes including destination, (same argument for destination) • Implementing Anonymity • Which Key Exchange mechanism? • Which nodes chosen? • Node failures?

17. Project • Authors acknowledge that an “omni present” adversary can break this scheme, so how strong an adversary can this scheme defend against? • Are there any weaknesses in the symmetric key distribution scheme? • How does a PRISM model compare with the author’s analysis of entropy, unlinkability, source/destination anonymity • Any other suggestions?

18. OTR Joseph Bonneau Andrew Morrison

19. OTR Goals • Authentication • Public Key Authentication. • Secrecy • AES Encryption of messages using symmetric keys. • Perfect Forward Secrecy • Short lived keys, discarded after use. Long lived keys are used to authenticate and generate new keys. • Repudiation • Use keyed MAC, and give out MAC values once used so that old messages are forgable.

20. OTR Protocol B A

21. PGPfone Jeremy Robin Andrew Schwartz

22. PGPFone • Philip Zimmermann’s protocol for secure VOIP • Designed to withstand online attacks • attacks on the physical premises

23. The Protocol Itself • Hello Packet • DHHash Packet • DHPublic Packet • Info Packet

24. Protocol, cont. • Users of the protocol are instructed to use a biometric word list to exchange the first few bytes of a hash of the shared secret • This relies on the human voice not being easily duplicated

25. Diameter Ryan Wisnesky Taral Joglekar

26. Diameter Overview The primary goal of the Diameter is to provide a way for application specific attribute-value pairs to travel, while enforcing basic authorization and accounting. • Messages are sets of arbitrary attribute value pairs and Diameter related bookkeeping fields. • Therefore, security services must be provided by other protocols. (It also means diameter messages can be used to implement other protocols…) • It does provide state machines for session management, routing, accounting, etc.

27. Idea 1: End-to-End Security • Diameter provides a way for messages to be routed. • Passive: message contents do not change, aside from routing info. • Active: message contents do change, according to a given policy. (We aren’t sure what exactly a policy can or can’t do yet.) • (Not unlike a hub vs. NAT’d router) • Diameter messages are processed at the application layer at each agent. Therefore, an alternative mechanism (i.e. hop-to-hop security isn’t going to work) is required to protect portions of the message at the application layer, to make sure that the proxies can’t mess with the session. • Allowing for a security association to be established through Diameter relays allows the participants to detect whether protected AVPs have been modified en-route, and hides sensitive data from intermediate agents. • What can a malicious proxy do? Interesting because proxy has access to everything

28. Idea 2: Accounting • Diameter provides a set of messages and state machine for keeping track of interesting events in a session. • e.g. user service termination • A security mechanism must be previously established before accounting can start. • Given a mechanism and intruder model, what can an intruder do to the statistics? • We’d be interested in results of the form ‘the statistics can be modified in this way’ as opposed to ‘the statistics can be modified’

29. Analysis of GODI (Group Domain of Interpretation) protocol Ju-Yi Kuo CS259 Project Proposal 2 / 2 / 2006

30. GODI Protocol • GODI (RFC 3547) protocol provides key management for a group of principals • Such protocol can be used to secure multicasting of voice or video among a group, or video-on-demand • Terminology: • GCKS: Group controller and key server. Responsible for distributing the group key to the group. It also adds new member to the group if requested, as well as deletes member from a group. • Sender, receiver: any principal in the group can securely send or receive traffic to the group.

31. GODI Protocol (cont.) • GODI requires a “phase 1” sub-protocol to first establish authentication & pair-wise key between GCKS and a principal. A shared secret SKEYID_a is also established. Then in phase 2, GODI performs group related operations. • The protocol defines 2 types of exchanges: • Group-Key Pull exchange • When a principal wants to join a group, it performs a 4-message exchange with the GCKS • Group-Key Push exchange • GCKS sends this message to distribute new key to the group. This can be performed when a member leaves the group.

32. GDOI Security Association Server Kas, Kbs, KEK • Kas and Kbs are pre-established pairwise keys established in phase 1, which secure the traffic between server and each principal. • KEK is Key-Encryption-Key. When Server wants to push down fresh TEK to members, it will be encrypted by the KEK. • TEK is Traffic-Encryption-Key between group members. It protects the communications between group member A and B. Alice Kas, KEK, TEK Bob Kbs, KEK, TEK

33. Group Key Pull excahnge S A M-ID , { HASH(1) , Ni , ID } Kas A is the initializer who wants to join the group and pull down group keys, and S is the responding GCKS server. • M-ID: a message ID that label this particular round of exchange • ID: this is the ID of the group that A wants to join. • Ni is the nonce from the initiator A. • HASH(1) is defined as: hash( SKEYID_a, M-ID , Ni , ID ) , where SKEYID_a is a shared secret established in phase 1 between A and S.

34. Group Key Pull excahnge (cont.) S A M-ID , { HASH(1) , Ni , ID } Kas M-ID , { HASH(2) , Nr , SA } Kas S responds without sending any key material, because S is not sure of A’s liveliness yet. • Nr is the nonce from the responder S. • SA: security association policy & parameters (crypto suite, key length, key lifetime, etc) • HASH(2) = hash( SKEYID_a , M-ID , Ni , Nr , SA )

35. Group Key Pull excahnge (cont.) S A M-ID , { HASH(1) , Ni , ID } Kas M-ID ,{ HASH(2) , Nr , SA } Kas • KE_I is the initiator’s half of the Diffie-Hellman key exchange, which will become the KEK. • CERT is the optional initiator’s certificate • HASH(3) = hash( SKEYID_a , M-ID , Ni , Nr , KE_I ) M-ID ,{ HASH(3) , KE_I [, CERT] } Kas

36. Group Key Pull excahnge (cont.) S A M-ID , { HASH(1) , Ni , ID } Kas M-ID ,{ HASH(2) , Nr , SA } Kas • KE_R is the responder’s half of the Diffie-Hellman key exchange • SEQ is a sequence number, which the server increments after each Group Key Pull and Group Key Push exchange. • KD: key download, which can be TEK • HASH(4) = hash( SKEYID_a , M-ID , Ni , Nr , KE_R , SEQ , KD ) M-ID ,{ HASH(3) , KE_I , CERT, POP_I } Kas M-ID ,{ HASH(4) , KE_R , SEQ , KD , CERT , POP_R } Kas

37. Group Key Push excahnge S A M-ID , { SEQ , SA , KD , [CERT ,] SIG } KEK When a member leaves or when key lifetime expires, the server will push down new key materials to all members. • SEQ is the sequence number. • SA: the new security association policy and parameters • KD: new key download, include new KEK and TEK • CERT: optional server certificate • SIG: signature of the entire message, signed by the server

38. Security Goals • The secrecy of the keys. • Perfect forward secrecy: if any member is compromised (pair-wise key leaked), the intruder cannot know the traffic that happens before that. • Authentication & integrity of the GCKS push messages • Freshness of keys. Old keys may not be re-used. • Security parameters (key length, lifetime, etc) are not altered. The Analysis • Phase 1 is assumed to be secure. It will not be analyzed here. • The RFC defines certain payloads to be optional. They will be included in the analysis. • Analysis tool : using either Murphi or Avispa.

39. SIP Greg Nelson Duc Pham

40. Basic Protocol INVITE Proxy INVITE Proxy INVITE B A Call Setup: OK OK OK ACK Call Session: “Blah blah blah…” B A “Yadda yadda yadda…” Call Termination: BYE B A OK

41. Vulnerabilities • Proxy Impersonation • Message Tampering • Session Teardown • Spoofed BYEs • Denial of Service • Malformed packets • REGISTER and INVITE flooding • Registration Hijacking

42. SIP Security • Registration hijacking • Authenticate originators of requests • Proxy impersonation • Authenticate servers • Message tampering • Secure body and certain headers end-to-end • Session teardown • Authenticate sender of BYE • Confidentiality so attacker can’t learn To, From tags • Denial of Service • Authenticate and authorize registrations

43. What We Will Do • Model basic protocol without security (Murphi or Avispa) • Some security mechanisms aren’t a “MUST” in the RFC, so they’re often left out in many implementations on the market! • Incrementally add security mechanisms (rational reconstruction) • Authentication • Message Integrity • DoS Protection • What are the consequences? • All vulnerabilities get fixed? • Introduces new unforeseen problems? • Some problems cannot be fixed?

44. Formalizing the Health Insurance Portability and Accountability Act (HIPAA) Simon Berring, Navya Rehani, and Dina Thomas 2nd Feb 2006

45. What is the HIPAA Privacy Law? • Providers and insurers must comply with your right to: • Ask and see a copy of your health records • Have corrections added to your health information • Receive a notice that tells you how your health information is used and shared • Decide whether to give your permission before your information can be used or shared for certain purpose • Ask to be reached somewhere outside your home • File complaints

46. Formalization in Temporal Logic • We interpret the standard (or a subset thereof) as a set of guarantees • We formalize the guarantees as security invariants • We use LTL tools (STep, SPIN) to verify the invariants for an implementation • We use typed, first order, linear temporal logic. • with types:  = Agent |Message | Property | Context • with grammar: • with invariants: • with norms(e.g.): inrole(p1, covered-entity) inrole(p2, individual) (q = p2) (tphi)

47. Goals and Challenges Rules - Permitted disclosures of PHI - Authorized use and disclosure - Notice and Individual Rights - Others.... Goals - Does a HCP's implementation of HIPAA violate protection of PHI? - What parts of these rules are essential for achieving protection? Challenges - Very little to no prior work - No unique mathematical interpretation to some textual rules - Very vast (to counter this we plan to use abstraction and/or concentration on a small part of the system)