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Wireless Network Security for Future Internet Yasuo Okabe Academic Center for Computing and Media Studies Kyoto University.

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Presentation on theme: "Wireless Network Security for Future Internet Yasuo Okabe Academic Center for Computing and Media Studies Kyoto University."— Presentation transcript:

1 Wireless Network Security for Future Internet Yasuo Okabe Academic Center for Computing and Media Studies Kyoto University

2 Overview 1.What is Network Security? 2.W-LAN Security Technologies 3.Security Issues on Public Wireless Internet Access Services 4.Location Privacy 5.Summary

3 1. What is Network Security? a brief introduction

4 What is Network Security? sender recipient message interruption eavesdropping masqueradefabricationmodification adversary?

5 Active Attacks and Passive Attacks Active attacks –Interruption denial of service (DoS) –Masquerade –Fabrication replay –Modification Passive Attacks –Eavesdropping (or Wiretapping) get the content of messages without the sender/recipient being aware of it –Monitoring observe who sends a message to whom at when Passive attacks are more difficult to detect than active attacks

6 Repudiation The sender denies the fact he have sent the message –The sender tells a lie. –The recipient tells a lie. –An adversary fabricated the message. The recipient denies the fact she have received the message –The sender tells a lie. –The recipient tells a lie. –An adversary masqueraded as the recipient. The received message is different from what is sent. –The sender tells a lie –The recipient tells a line –An adversary modified it. sender recipient message Both adversary? It is meaningless one can believe firmly the opponent tells a lie but he cannot prove it to a third person.

7 Network Security Attributes in Computer Security –Confidentiality –Integrity –Availability Concealment assure to be kept unnoticed the fact communication is done between the sender and the recipients to others Authentication confirm both the sender and the recipients surely have the authority to do the act a the communication Nonrepudiation prevent either the sender or the recipient from denying the communication When a message is sent, the recipient can prove that the message is sent from the sender, and vice versa.

8 2. W-LAN Security Technologies

9 Wireless LAN IEEE –A set of standards for wireless local area networks (W-LAN) –Developed by IEEE LAN/MAN Standards Committee (IEEE802). IEEE (1997), 11b (1999), 11a (1999), 11g(2003) IEEE i (2004) Wi-Fi (Wireless Fidelity) –A family of related specifications based on IEEE but slightly modified. –Specified by Wi-Fi Alliance

10 W-LAN Security Access Control at Access Points –Stealth ESSID stop announcement of ESSID (Extended Service Set ID) But, ESSID can be sniffed by monitoring. –MAC Address Registration deny packets from a client whose MAC addresse is not registerred But, MAC addresses can be sniffed and be spoofed. –WEP, WPA, … T.B.D. later Restriction at Access Points –IP address restriction port filtering –Disabling direct communication among clients

11 WEP (Wired Equivalent Privacy) Authentication and Encryption by a WEP Key –64bit WEP (40bit key 24bit IV) –128bit WEP (104bit key 24bit IV) Two mode of authentication –Open System authentication No actual authentication at association, but data is encrypted by WEP key –Shared Key authentication Four-way challenge-response handshake at association

12 WEP Encryption Details WEP key IV Key stream RC4 Data (plain text)ICV CRC32 (Integrity Check Value) XOR (exclusive OR) Data (encrypted)ICV (encrypted) MAC headerIVFCS (Frame Check Sum) (Initial Vector) IV and hence key stream are frequently changed, so as to protect against brute-force attack.

13 Vulnerability of WEP Relatively shortness of IV – ,000,000 The same number of packets may be sent only in 10 minutes in 54Mbps W-LAN. –Crackers can get the XOR of plain-text data if he find two frames with the same IV (D1+K) + (D2+K) = D1+D2, where D1 and D2 are original data and K is the key stream. Key remains static –sometimes yearly… RC4 is known to be weak. Note that cracking can be done passively

14 Cracking Tools AirSnort –http://airsnort.shmoo.com/http://airsnort.shmoo.com/ Aircrack-ng –http://www.aircrack-ng.orghttp://www.aircrack-ng.org

15 demo

16 WPA (Wi-Fi Protected Access) WPA-TKIP –Improvement of WEP –Use a temporal key instead of WEP key Key is assigned per client, per association and periodically changed TKIP: Temporal Key Integrity Protocol –Key stream is generated by RC4 from 48bit IV (initial vector) avoid reuse same IV. WPA-AES –Use of AES (Advanced Encryption Standard) instead of RC4.

17 WPA-PSK WPA-PSK (Pre- Shared Key) –Replacement of WEP Initial association between AP and client is done with a pass phase as a pre-shared key Weakness –Attacker who have the pre-shared key can eavesdrop all packets. –Dictionary attack may succeed if the pre- shared key is not choose enough long and not guessable.

18 WPA-EAP EAP (Extensible Authentication Protocol) Authentication based on 802.1x with a Radius authentication server EAP-TLS –Based on PKI –Server and client mutually authenticate by certificates EAP-PEAP –ID/Password based Use of PKI is optional –MS-CHAP v2 Server and client mutually authenticate via ID/password EAP-SIM –Using SIM (GSM Subscriber Identity Module) Mobile Node Access Point Corresponding Node Authentication Server

19 Comparison of IEEE802.1X EAP-TLS EAP Extensible Authentication Protocol) Client Authentication Server Authentication Security Level Operation Cost EAP-TLSCertificate High EAP-TTLSID/PasswordCertificateMid. EAP-PEAPID/PasswordCertificateMid. LEAPID/Password Low EAP-MD5ID/Password---Low

20 Smart Card CA Administrator RA Administrator RA Operator User RA CA Apply Identify Authorize Issue Certificate Application Server (web) Admin Server (web) Authority Delegation Issue Request How to use EAP-TLS based on PKI APRADIUS LDAP

21 OpenWRT –Alternative firmware for commodity W-LAN routers Supports many platforms, including Buffalos products –Open source based on Linux CLI Supports many features like 802.1x with Radius, VPN, etc. Customizable by users themselves. DD-WRT A branch of OpenWRT GUI

22 3. Security Issues on Public Wireless Internet Access Service

23 Status of public wireless Internet access Remarkably rapid deployment of IEEE802.11b/g W-LAN in these 10 years –Now almost all Note PCs have W-LAN build in. –Security risks/incidents have become a social problem. Public wireless LAN or wireless HotSpot –Public Internet Access Service using W-LAN technology Attracts attention of the mass media. –In U.S. Bankruptcy of MobileStar (2001) –In Japan Paid services are not necessarily satisfactory –MIS stops the service 2002 –Livedoor Wireless canceled the plan of extending the coverage –Each of NTT group company provides service in unsystematic way. HOTSPOT (NTT.com), M-Zone (NTT DoCoMo), Wireless LAN Club (NTT BP), FletsSpot (NTT East/West)

24 Difficulty in the business model of public wireless Internet access service Issues in cover area –Conflict among service providers at public hot spots like railway stations, airports, hotels Number of channels of IEEE802.11b/g is very small –In most places only one service available Users who subscribes the service can use it. –Most of the spots are located at metropolis, few in local cities. –Covers only spots, not area Enormous investment is needed to cover area, compared to 3G mobile phone service Several projects conducted by local governments are suspended in U.S.

25 Free Wireless Services FON –http://www.fon.comhttp://www.fon.com Google WiFi –http://wifi.google.comhttp://wifi.google.com eduroam –http://www.eduroam.orghttp://www.eduroam.org FreeSpot –http://www.freespot.comhttp://www.freespot.com

26 Google WiFi A free wireless Internet service in Mountain View by Google –More than 400 APs. –Service area: almost the whole areal of 18km 2 –Unique user 15,000/month We're offering to the city of Mountain View as part of our ongoing efforts to reach out to our hometown.

27 eduroam –W-LAN roaming architecture among academic and research institutes in Europe and other countries. –IEEE802.1x (EAP-TTLS) raduis federation –Roaming between commercial service providers in Europe (experimental)

28 Is FREE service really possible? We already have Internet Infrastracuture. –Most of office/shops/houses have broadband access. ADSL (1 10Mbps) FDDH (100Mbps 1Gbps) Providing it to visitors is feasible –We rarely consumes the bandwidth fully –Wireless service needs little cost. The issue is security –Risk of providing network access to unknown visitors Access to the private network can be prohibited but Malicious access to the Internet is hard to limit

29 Security in public wireless Internet services What is the difference between W-LAN and public Wireless Access? –For users: Eavesdropping, MIM (man-in-the-middle) attack Masquerading (Impersonation) –For host people of access points Accounting (in paid service only) Avoiding anonymous use

30 Limitation of Wireless-LAN authentication and encryption technologies for public wireless service Stealth ESSID? –ESSID must be announced to public MAC address filtering –Can very easily be spoofed –Issues in scalability WEP (encryption) –Pre-shared key –The key is shared by all users WPA-EAP –IEEE802.1x Cannot be used in public services. Encryption is done only in Wireless section (between AP and client)

31 ISP type W-LAN service Features –Centralized Management by ISP Wireless AP and Access Network are owned by ISP ISP manages Authentication Server and issues acounts –Subscriber must rely on ISP Issues –Contract is needed between the ISP and subscribers AS: authentication server AP: access point MN: mobile node CN: corresponding node Mobile Node Corresponding Node ISP Network Access Point Authentication Server Data Authorization 1. 2.

32 Wireless Internet Service by a single ISP MN (mobile node) Auth Server AP (Access Point) ISP Internet CN (corresponding node) Mutual Authentication ISPs private network Mutual trust relation

33 WLAN roaming among ISPs MN Access points Roam ISP Internet CN Authentication Home ISP AAA server (exapmple) iPass eduroam Mutual trust relation Trust relation between Home ISP And Roam ISP is necessary

34 Self-managed model Features –Managed typically with one or a few APs, independently Daily operational cost is not so high. –Security policy depends on the host person –Grass-root deployment is possible Issues –Very costly to assure security level as high as the user can be traced when an incident occurs. –No protection if the host person has malicious attempt. Corresponding Node Mobile Node Access Point Host persons network (1.) 2.

35 Self-managed FreeSpot Free Service MN AP Internet CN Host person of APs Naïve authentication Malicious adversary Eavesdrop Masquerade Fabrication Repudiation

36 Management Cost High Low Self-Managed Model ISP Model Autonomous Distributed Model Framework to enhance the security of self-managed network model Security High Low Comparison of Public WLAN Service Models

37 AP hosts Network Network of Authentication System Corresponding Node Mobile Node Access Point Authentication Server Authentication Data Authorization assuming little confidentiality Autonomous Distributed Model

38 Data Path No Auth. at AP Auth. at AP TunnelPATPRATP DirectPADPRADP [ Properties and Name of Each Model ] Categorization of Security Procedures of Autonomous Distributed Public WLAN services Categorize authentication mechanisms based on the following two aspects: Authentication Transaction at Access Point Relayed Passed Through Data Path Tunneling Direct [ Pros and Cons of Four Models ] Authentication Treatment at AP Relayed: Eliminate malformed authentication Make an AP busier Data Path Tunneling: Acquire location privacy of MNs Detour via AS is forced In the other case, pro and con go across.

39 Corresponding Node Tunneling Server Access Point Mobile Node Passed-through Authentication, Tunneling Path (PATP) Model VPN Tunnel Authentication Data Authorization Tunneling & Authentication Server Corresponding Node Access Point Mobile Node (Relay of 1.) Relayed Authentication, Tunneling Path (RATP) Model [ ]

40 Authentication Data ID Info. Exchange Authentication Server Corresponding Node Mobile Node Access Point Passed-through Authentication, Direct Path (PADP) Model Mobile Node Access Point Corresponding Node Authentication Server Relayed Authentication Direct Path (RADP) Model [ ]

41 Implementation in MIAKO.net MN AP Internet CN AP hosts Users own or By ISP VPN server Mutual trust relation Pass through but VPN protocols only

42 4. Location Privacy

43 What is Location Privacy? Location privacy is the combination of information of when and where you are, and who you are Your location privacy is expected to be disclosed to neither of – corresponding node – authentication server – access point Trade off with –Anonymity v.s. security –Location-aware service Corresponding Node Mobile Node Access Point Authentication Server You are here!

44 Location privacy in ISP type W-LAN service The authentication server knows – who you are – where you are now – To whom you are communicating Users are forced to rely on the service provider –Mobile phone carriers does. Mobile Node Corresponding Node Access Point Authentication Server Data Authorization 1. 2.

45 Corresponding Node Mobile Node Access Point Authentication Server Location Privacy in Roaming Service Authentication server knows who you are where you are Access point may know where you are who you are to whom you are communicating Corresponding node will know where the MN is

46 Corresponding Node Mobile Node Access Point Authentication Server How pseudonym conceals location privacy in roaming service Access point may know where you are to whom you are communicating which is your home ISP, not who you are Authentication server may know who you are which roam ISP you are using, not where you are Access with pseudonym Authentication proxy server Home ISP Roam ISP

47 Corresponding Node Tunneling Server Access Point Mobile Node Location privacy in VPN-based Tunneling Path Model VPN Tunnel Data Authorization Roam ISP Home ISP Authentication server knows who you are where you are Access point cannot know to whom you are communicating Corresponding node cannot know where the MN is

48 5. Summary

49 Summary Security issues of W-LAN roaming services Proposal of autonomous distributed public wireless Internet access architecture –MIAKO.net –A service model for implementing ubiquitous networking with a grass-root W-LAN roaming with enough security.

50 [ Concluding Remarks ] Categorized security problems of public WLAN services Proposed an Autonomous Distributed public WLAN service model Compared some security procedures of Autonomous Distributed public WLAN service Each procedure has its pros and cons therefore we cannot say which is the best for future use MIAKO.NET public wireless service This is based on PATP model [ References ] A. Balanchandran et al., Wireless Hotspots: Current Challenges and Future Cirections, 2003 N. Borisov et al., (In)Security of the WEP Algorithm, 2001 D. Golombek, Single Computer Breaks 40-bit RC4 in under 8 Days, 1996 T. Komura et al., The MIAKO.NET Public Wireless Internet Service in Kyoto, 2003 Y. Matsunaga et al., Secure Authentication System for Public WLAN Roaming, 2003 L. Ackerman et al., Wireless Location Pricay: Low and Policy in the U.S., EU and Japan, - ISOC Member Brefing, 2003


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