Introduction Outline to Wireless Security
Lecture 10
The importance of Wireless communications Wireless networks and security risks
Why is it so hard to secure wireless communications?
Wireless communications and network security issues
WEP WAP Bluetooth (reading) WWAN and security (reading)
Principles for securing a wireless network
What need to be done to secure a wireless network?
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References
http://www.practicallynetworked.com/t ools/wireless_articles_security.htm http://www.cs.rice.edu/~astubble/wep/ wep_attack.pdf http://www.drizzle.com/~aboba/IEEE/ http://www.hpl.hp.com/personal/Jean_ Tourrilhes/Linux/ http://www.cis.ohiohttp://www.cis.ohiostate.edu/~jain/refs/wir_refs.htm
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Importance of wireless communications Growing of Wireless Devices
Huge growth of wireless communication devices, wireless laptops, PDA, handheld PC, Mobile phone, etc.
Pictures borrowed from other authors
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Wireless Networks and Mobile Commerce services
Entertainment
Music Games Graphics Video etc
Wireless Communication Usage
Internet revolution has lead to the emergence of e-commerce emarket Around 105 million Yahoo! subscribers in 2001 Expansion of Wireless devices has lead to the explosive growth of mobile communications More than 200 million wireless subscribers in 2001 Around 1 billion by 2004 (estimated)
Communication
e-mail Chatrooms Video-conferencing etc
Wireless services m-commerce
Transactions
Banking Broking Shopping Auctions Betting Booking & reservations etc
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News City guides Directory services Maps Traffic & weather Corporate information etc
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Wireless & Internet convergence has lead to the explosion of the Mobile Commerce market Very High number in the future!
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Wireless connections End-to-End Simple Wireless LAN End- to-
Simple Wireless LAN (e.g) (e.g)
Access Point
WNIC WNIC
users
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WLAN Protocol Setup
LAN Access Point Shared Key Mobile Station Mobile Station Mobile Station
A Possible Wireless Network (e.g) (e.g)
e-businesses
Internet
Internet
users
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Example of a WLANs
Try to find out if there is a WLAN on Caulfield campus Try to find out who else has a WLAN in Melbourne (in the city area) Check other university campuses, hotels with conference rooms, libraries, etc.
Wireless Computing and Security
Wireless computing offers many benefits:
Portability Flexibility Increased productivity Lower cost installations
Wireless computing provides new working environments and imposes new security issues.
Protecting the networks against attacks, ensuring secure data transmission, detecting and tracking down any penetration to a wireless network are difficult.
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Wireless Communications and Risks
Risks
Wireless technology has not advanced fast enough to allow better security mechanisms to be implemented. Currently wireless traffic is not secure
E.g: sensitive data may be transmitted over unsecured E.g: connections
Credit Card numbers Corporate email Usernames/passwords
Wireless Network Security Issues
Wireless devices are radios and radios have limitations in capacity
Wireless communication medium is the airwave and openly exposed to intruders A wireless port of a wireless Local Area Network (WLAN) is logically equivalent to an Ethernet port without any protection Possible loss of confidentiality and integrity and the thread of denial of service
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Expert hackers can access wireless networks easier than wired ones Security holes in wireless systems can be quickly found with the ideas and tools that have been used with wired networks
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Wireless LAN Security Issues (e.g) (e.g)
Cracking the encryption key
Reading and decrypting wireless LAN packets are not as hard as in the case of wired networks due to the key generation problems
Wireless LAN Security - Background
Most Wireless Network Interface Card (WNIC) and Access Point (AP) are used for WLAN Each WNIC or AP must be manually configured with some shared key The sending and receiving stations/AP share a secret key A sending station encrypts each frame before transmission Receiving station decrypts the frame
Unauthorised accessing
An unregistered user can easily access to a wireless LAN resource if an Access Point is not correctly configured. The user can also access to the main wired network via the wireless LAN
Authorised users abusing the systems, eg: eg:
Unauthorised sniffing of other traffic by users Eavesdropping on other users traffic
Setting up phantom Access Points to gather data from genuine users Setting up an unknown wireless LAN inside a corporation => making wired network more vulnerable
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Wireless LAN Security - 802.x, 802.11b (commercial name as WiFi),etc. WiFi),etc.
The 802.x
Family of standards set forth by IEEE to define the specifications for wireless LANs: Wireless Medium Access Control (WMAC):
regulate access to the medium Use 48 bits as Ethernet addresses on wired LANs
IEEE 802.X standards
Physical Layer Specifications
Spectrum, distance, bit rate, etc
Borrowed from RFC
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Security problems with WLANs
Easy access: signals fly into the air Rouge Access Point
Set up by experts or normal users
Wireless LAN Security - WEP
Wired Equivalent Privacy (WEP) Designed by the IEEE aimed to prevent eavesdroppers and unauthorised connections to a wireless network WEP tries to achieve similar security as a wired LAN
Confidentiality: protect the contents of wireless trafic Access Control: prevent an adversary from using your wireless network Data Integrity: prevent the modification of data in transit
Unauthorised access to services
Majority of access points are put in services with minimum modifications to their default configuration
Denial of services
Attackers can inject traffic into a wireless network without being being attached to an AP; A ping flood can be launched from a wired network to overwhelm the limited-capacity wireless devices limited-
WMAC spoofing and session hijacking
Attackers can observe MAC addresses of stations and adopt those addresses for malicious transmissions
Traffic analysis and eavesdropping
Frame headers can be transmitted in the clear form and are visible to anybody with a wireless network analyser
Chain attacks to wired networks via a wireless one
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Security with WEP
Security with WEP
A secret key (k) shared between the communicating parties is distributed and each packet is encrypted with shared secret key + initialization vector (IV) [24 bits] The sender: Computes a checksum c(M) Picks an IV v, and generate a keystream RC4(v,k) XORs <M,c(M)> with the keystream to get the ciphertext Transmits v and the ciphertext over the radio link Upon receipt, the receiver: Uses the transmitted v and the shared k to generate the keystream RC4(v,k) XORs the ciphertext with RC4(v,k) to get <M',c'> Checks to see if c' = c(M') If it is, accepts M' as the message transmitted
ciphertex
RC4(iv,k)
ciphertex
iv the initialization a vector, random sequence of bits k the secret key RC4 a stream cipher, believed to be secure
Takes in an initialization vector and key; produces a key key; stream
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WEP and Security Issues
The keystream for WEP is RC4(v,k), which depends only on v and k. k is a fixed shared secret, that is rarely changed In many setups, many users share the same k So the keystream depends only on v If two packets ever get transmitted with the same value of v, you reuse the keystream, which is keystream, vulnerable Since v gets transmitted in the clear form for each packet, an attacker can easily tell when a value of v is reused How many possible values of v are there? v only occupies 24 bits of the header, so at most there are 2^24 After 2^24 packets, there will be a repeat one!
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Wireless LAN Security with WEP
Since IV is relatively short & shared keys that remain static, eventually WEP may use the same IV for different data packets for a large busy network in a short period of time If you can collect enough packets based on the same IV, you can work out the secret key 802.11 with WEP does not provide any functions that support the exchange of keys among stations => system administrators or users generally use the same keys for a long time
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WEP and its Vulnerabilities
WLAN tools that recover encryption keys
Exploits weakness in Key Scheduling Algorithm of RC4 Requires 5-10 million encrypted packets 5Once enough packets have been gathered, can guess the encryption key in under a second For more information:
http://airsnort.sourceforge.net/ http://airsnort.sourceforge.net/ http://wepcrack.sourceforge.net/ http://wepcrack.sourceforge.net/
Wireless attacks (e.g) (e.g)
Session hijacking
Occurs because of race conditions in 802.x and 802.x state machines A hacker waits for successful authentication Then, breaks the users connection and user impersonates her The hacker can exploit the users session until user timeout
Man-in-the-Middle Man- in- theSince 802.x uses only one-way authentication a onehacker can act as an AP to users APs are trusted entities => bad design=> security problems for WLANs
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WEP and Security Concerns
802.x with WEP is not enough Should put more things together for security Need another encryption protocol provide better security Problems
Need hardware acceleration Optimize for speed and efficiency Tradeoff in security scheme
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Wireless LAN Security Enhanced WEP
Digital Certificates can be used for distributing keys dynamically to WLAN
Solves key re-use problem re-
Enhance authentication between clients and APs via an authentication server Increase key length and change keys after a certain number of frames
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Wireless Application Protocol (WAP)
WAP tries to provides Authentication Confidentiality Integrity WAP security gateway Server product dedicated to providing WTLS sessions Works with todays WAP phones today
Wireless Application Protocol (WAP)
Designed to provide Internet connections for wireless users, particularly mobile phone users Employs WML, WTLS Uses WAP Identity Module to provide resistance to device-tampering device-
WTP/WTLS
HTTP/SSL
WAP Gateway Internet
Web Web Server Server
users
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Wireless Application Protocol (WAP)
A WAP-enable mobile phone can execute an application that WAPrequests a URL or runs a script on a standard web server The agent on the phone sends an URL requests to a WAP gateway in the form specified by WTP (wireless Transaction Protocol) WAP gateway translates the request into HTTP request (if the The gateway forwards (or encrypts then forwards) the (HTTP/HTTPS) request to the web server Web server processes the request and returns the results to the gateway (using HTTP/SSL) The gateway receives the results and does necessary translations (if it is not done by a WAP server) and decryptions The gateway then sends the results to the phone
WAP Security
The security of WAP systems is left to architects and developers WTLS does not provide end-to-end security end- toWAP has common limitations as other wireless technologies such as size, space, and speed. WAP gateways are trusted to encrypt and decrypt data WML and WML script are l...