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Wireless Network Security for Future Internet

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Presentation on theme: "Wireless Network Security for Future Internet"— Presentation transcript:

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

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

3 1. What is Network Security? a brief introduction

4 What is Network Security?
sender message recipient adversary? interruption eavesdropping masquerade fabrication modification

5 Active Attacks and Passive 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 ? ? sender message recipient adversary? 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 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. }Both 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 Authentication
Confidentiality Integrity Availability 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. Concealment assure to be kept unnoticed the fact communication is done between the sender and the recipients to others

8 2. W-LAN Security Technologies

9 Wireless LAN IEEE802.11 Wi-Fi (Wireless Fidelity)
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
CRC32 Data (plain text) ICV (Integrity Check Value) RC4 XOR (exclusive OR) WEP key Key stream IV (Initial Vector) (encrypted) MAC header IV Data (encrypted) ICV FCS (Frame Check Sum) IV and hence key stream are frequently changed, so as to protect against brute-force attack.

13 Vulnerability of WEP Relatively shortness of IV Key remains static
224 ≒ 16,000,000 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 Aircrack-ng

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) Weakness
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) EAP-TLS
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) Corresponding Node Authentication Server Access Point Mobile Node

19 Comparison of IEEE802.1X EAP-TLS
EAP (Extensible Authentication Protocol) 方式 Client Authentication Server Authentication Security Level Operation Cost EAP-TLS Certificate High EAP-TTLS ID/Password Mid. EAP-PEAP LEAP Low EAP-MD5 ---

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

21 OpenWRT
Alternative firmware for commodity W-LAN routers Supports many platforms, including Buffalo’s 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 (, 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 Google WiFi eduroam FreeSpot

26 Google WiFi A free wireless Internet service in Mountain View by Google More than 400 APs. Service area: almost the whole areal of 18km2 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 Corresponding Node ISP Network Authentication Server Access Point 1. 2. AS: authentication server AP: access point MN: mobile node CN: corresponding node Authorization Data Mobile Node

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

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

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 2. Host person’s network Access Point (1.) Mobile Node

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

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

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

38 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. [ Properties and Name of Each Model ] Data Path No Auth. at AP Auth. at AP Tunnel PATP RATP Direct PADP RADP

39 [ ] [ ] Relayed Authentication, Passed-through Authentication,
Tunneling & Authentication Server 2. 4. Corresponding Node Corresponding Node 5. Tunneling Server 2. (Relay of 1.) 1. Access Point 3. Access Point Authorization 1. Authentication VPN Tunnel Data Mobile Node Mobile Node [ ] [ ] Passed-through Authentication, Tunneling Path (PATP) Model Relayed Authentication, Tunneling Path (RATP) Model

40 [ ] [ ] Passed-through Authentication, Direct Path (PADP) Model
Corresponding Node 4. 2. Corresponding Node 3. 3. Authentication Server 1. 2. Authentication Server Access Point Access Point ID Info. Exchange 1. Authentication Data Mobile Node Mobile Node [ ] Passed-through Authentication, Direct Path (PADP) Model [ ] Relayed Authentication Direct Path (RADP) Model

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

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 Authentication Server Corresponding Node Access Point Mobile Node 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. Corresponding Node Authentication Server Access Point 1. 2. Authorization Mobile Node Data

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

46 How pseudonym conceals location privacy in roaming service
Home ISP Authentication Server 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 Corresponding Node Roam ISP Access Point Authentication proxy server Access with pseudonym Mobile Node

47 Location privacy in VPN-based Tunneling Path Model
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 Corresponding Node Tunneling Server Access Point Roam ISP Authorization VPN Tunnel Data Mobile Node

48 5. Summary

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

50 Categorized security problems of public WLAN services
[ 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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