5169 wireless network_security_amine_k

Wireless Networks and Mobile Computing (CSI 5169)

Wireless Network Security

Amine Khalife akhal0 1 6 @ uo ttawa. ca

Outline

1. Wireless intro & history

2. Wireless network modes

3. SSID

4. WEP

5. WPA

6. WPA2

7. Wireless Network tools

8. References


Background & Overview History

Developed for military use Security widely noticed after Peter Shipley’s 2001 DefCon

preso on War Driving DHS labeled Wi-Fi a terrorist threat, demanded regulation

Non Wi-Fi types CDPD – 19.2 kbps analog GPRS – 171.2 kbps digital WAP – bandwidth-efficient content delivery Ricochet – 176 kbps wireless broadband flop Bluetooth – personal area networks, range limited only by

transmit power Blackberry – Use cellular & PCS networks, no

authentication at console IEEE 802 series standards

802.11 – wireless LANs 802.15 – wireless personal area networks (e.g., Bluetooth) 802.16 – wireless broadband up to 155Mb, wireless ISPs


802.11 Standards

802.11a – 54 Mbps@5 GHz Not interoperable with 802.11b Limited distance Dual-mode APs require 2 chipsets, look like two APs to

clients Cisco products: Aironet 1200

802.11b – 11 [email protected] GHz Full speed up to 300 feet Coverage up to 1750 feet Cisco products: Aironet 340, 350, 1100, 1200

802.11g – 54 [email protected] GHz Same range as 802.11b Backward-compatible with 802.11b Speeds slower in dual-mode Cisco products: Aironet 1100, 1200


802.11 Standards (Cont.)

802.11e – QoS Dubbed “Wireless MultiMedia (WMM)” by Wi-Fi Alliance

802.11i – Security Adds AES encryption Requires high cpu, new chips required TKIP is interim solution

802.11n –(2009) up to 300Mbps 5Ghz and/or 2.4Ghz ~230ft range

802.11ac – (under development) Will provide high through put in the 5 GHz band Will use wider RF bandwidth will enable multi-station WLAN throughput of at least 1

Gbps a maximum single link throughput of at least 500 Mbps


Wireless Network Modes

The 802.11 wireless networks operate in two basic modes:1. Infrastructure mode2. Ad-hoc mode

Infrastructure mode: each wireless client connects directly to a central

device called Access Point (AP) no direct connection between wireless clients AP acts as a wireless hub that performs the

connections and handles them between wireless clients


Wireless Network Modes (cont’d)

The hub handles: the clients’ authentication, Authorization link-level data security (access control and

enabling data traffic encryption) Ad-hoc mode:

Each wireless client connects directly with each other No central device managing the connections Rapid deployment of a temporal network where no

infrastructures exist (advantage in case of disaster…) Each node must maintain its proper authentication

list


SSID – Service Set Identification

Identifies a particular wireless network A client must set the same SSID as the one in that

particular AP Point to join the network Without SSID, the client won’t be able to select and join

a wireless network Hiding SSID is not a security measure because the

wireless network in this case is not invisible It can be defeated by intruders by sniffing it from any

probe signal containing it.


SSID (Cont’d)

A way for vendors to make more money So easy to find the ID for a “hidden” network because

the beacon broadcasting cannot be turned off Simply use a utility to show all the current networks:

inSSIDer NetStumbler Kismet


IEEE 802.11 Security – Access control list

Access control list Simplest security measure Filtering out unknown users Requires a list of authorized clients’ MAC addresses to

be loaded in the AP Won’t protect each wireless client nor the traffic

confidentiality and integrity ===>vulnerable Defeated by MAC spoofing:

ifconfig eth0 hw ether 00:01:02:03:04:05 (Linux)SMAC - KLC Consulting (Windows)MAC Makeup - H&C Works (Windows)


WEP - Wired Equivalent Privacy

The original native security mechanism for WLAN provide security through a 802.11 network Used to protect wireless communication from eavesdropping

(confidentiality) Prevent unauthorized access to a wireless network (access

control) Prevent tampering with transmitted messages Provide users with the equivalent level of privacy inbuilt in

wireless networks.


WEP

1. Appends a 32-bit CRC checksum to each outgoing frame (INTEGRITY)

2. Encrypts the frame using RC4 stream cipher = 40-bit (standard) or 104-bit (Enhanced) message keys + a 24-bit IV random initialization vector (CONFIDENTIALITY).

3. The Initialization Vector (IV) and default key on the station access point are used to create a key stream

4. The key stream is then used to convert the plain text message into the WEP encrypted frame.


Encrypted WEP frame


RC4 keystream XORed with plaintext


WEP Components

Initialization Vector IV Dynamic 24-bit value Chosen randomly by the transmitter wireless network

interface 16.7 million possible keys (224)

Shared Secret Key 40 bits long (5 ASCII characters) when 64 bit key is used 104 bits long (13 ASCII characters) when 128 bit key is used


WEP Components (cont’d)

RC4 algorithm consists of 2 main parts:

1. The Key Scheduling Algorithm (KSA): involves creating a scrambled state arrayThis state array will now be used as input in the

second phase, called the PRGA phase.

1. The Pseudo Random Generation Algorithm(PRGA):The state array from the KSA process is used here to

generate a final key stream. Each byte of the key stream generated is then Xor’ed

with the corresponding plain text byte to produce the desired cipher text.


WEP Components (cont’d)

ICV (Integrity Check Value)= CRC32 (cyclic redundancy check) integrity check

XOR operation denoted as ⊕ plain-text keystream= cipher-text⊕ cipher-text keystream= plain-text⊕ plain-text cipher-text= keystream⊕


How WEP works


IV

RC4key

IV encrypted packet

original unencrypted packet checksum

Encryption Process


Decryption Process


WEP Authentication

1. The station sends an authentication request to AP2. AP sends challenge text to the station.3. The station uses its configured 64-bit or 128-bit default key to

encrypt the challenge text, and it sends the latter to AP.4. AP decrypts the encrypted text using its configured WEP key

that corresponds to the station's default key. 5. AP compares the decrypted text with the original challenge

text. 6. If the decrypted text matches the original challenge text, then

the access point and the station share the same WEP key, and the access point authenticates the station.

7. The station connects to the network.


WEP Authentication (Cont’d)


WEP Authentication (Cont’d)

There is a well-documented vulnerability with shared-key authentication.

The authentication process leaks information about the key stream

It is possible to derive the keystream used for the handshake by capturing the challenge frames in Shared Key authentication.

SKA is regarded as insecure. The problem is that a monitoring attacker can observe both the

challenge and the encrypted response.he can determine the RC4 stream used to encrypt the

response, He can use that stream to encrypt any challenge he

receives in the future


WEP flaws and vulnerabilities

Weak keys: It allows an attacker to discover the default key

being used by the Access Point and client stations This enables an attacker to decrypt all messages

being sent over the encrypted channel. IV reuse and small size:

There are 224 different IVs On a busy network, the IV will surely be reused, if

the default key has not been changed and the original message can be retrieved relatively easily.


WEP flaws and vulnerabilities (cont’d)

With IV reuse, it is possible to determine keystreams and hence enable an attacker to forge packets obtaining access to the WLAN.

If WEP is using 40 bit long key then it will need more protection from attacks as compared to 128 bit long WEP key. Hence, both are very weak and unable to provide the security to Wi-Fi Networks.

uses weak authentication algorithm uses weak data encapsulation method The use of improper integrity algorithm i.e. CRC-32 Lack of mutual authentication and key management


Attacks on WEP


WEP encrypted networks can be cracked in 10 minutes

Goal is to collect enough IVs to be able to crack the key

IV = Initialization Vector, plaintext appended to the key to avoid Repetition

Injecting packets generates IVs

Attacks on WEP

Backtrack 5 (Released 1st March 2012)

Tutorial is available

All required tools on a Linux bootable CD + laptop + wireless card


WEP cracking example


WPA - WI-FI Protected Access

New technique in 2002 replacement of security flaws of WEP. Improved data encryption Strong user authentication Because of many attacks related to static key, WPA

minimize shared secret key in accordance with the frame transmission.

Use the RC4 algorithm in a proper way and provide fast transfer of the data before someone can decrypt the data.


WPA

Data is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV).

One major improvement in WPA over WEP is the Temporal Key Integrity Protocol (TKIP), which dynamically changes keys as the system is used.

When combined with the much larger IV, this defeats the well-known key recovery attacks on WEP.

WPA also provides vastly improved payload integrity.


WPA

A more secure message authentication code (usually known as a MAC, but here termed a MIC for "Message Integrity Code") is used in WPA, an algorithm named "Michael".

The MIC used in WPA includes a frame counter, which prevents replay attacks being executed.

The Michael algorithm is a strong algorithm that would still work with most older network cards.

WPA includes a special countermeasure mechanism that detects an attempt to break TKIP and temporarily blocks communications with the attacker.


WPA


How WPA Addresses the WEP Vulnerabilities

WPA wraps RC4 cipher engine in four new algorithms1. Extended 48-bit IV and IV Sequencing Rules

248 is a large number! More than 500 trillionSequencing rules specify how IVs are selected and

verified2. A Message Integrity Code (MIC) called Michael

Designed for deployed hardwareRequires use of active countermeasures

3. Key Derivation and Distribution Initial random number exchanges defeat man-in-the-

middle attacks4. Temporal Key Integrity Protocol generates per-

packet keys


WPA2 - WI-FI Protected Access 2

Based on the IEEE 802.i standard 2 versions: Personal & Enterprise The primary enhancement over WPA is the use of the

AES (Advanced Encryption Standard) algorithm The encryption in WPA2 is done by utilizing either

AES or TKIP The Personal mode uses a PSK (Pre-shared key) &

does not require a separate authentication of users The enterprise mode requires the users to be

separately authenticated by using the EAP protocol


WPA2

WPA uses AES with a key length of 128 bit to encrypt the data

The AES uses the Counter-Mode/CBC-MAC Protocol (CCMP)

The CCMP uses the same key for both encryption and authentication, but with different initialization vectors.


WPA2

WPA2 has immunity against many types of hacker attacks Man-in-the middle Authentication forging Replay Key collision Weak keys Packet forging Dictionary attacks


WPA2 weaknesses

Can’t protect against layer session hijacking

Can’t stand in front of the physical layer attacks: RF jamming Data flooding Access points failure

Vulnerable to the Mac addresses spoofing


Am I secure if I use WPA-PSK

WPA-PSK protected networks are vulnerable to dictionary attacks

Works with WPA & WPA2 (802.11i) New attack techniques have increased the speed of this attack

– CowPatty 4.6 Run CowPatty against packets to crack the key Needs SSID to crack the WPA-PSK, easily obtainable! Also supports WPA2-PSK cracking with the same pre-

computed tables! Spoof the Mac address of the AP and tell client to disassociate Sniff the wireless network for the WPA-PSK handshake (EAPOL)


WPA Cracking Example


WEP vs WPA vs WPA2


WEP WPA WPA2

ENCRYPTION RC4 RC4 AES

KEY ROTATION NONE Dynamic Session Keys

Dynamic Session Keys

KEY DISTRIBUTION

Manually typed into each device

Automatic distribution

available

Automatic distribution

available

AUTHENTICATION

Uses WEP key as Authentication

Can use 802.1x & EAP

Can use 802.1x & EAP

Procedures to improve wireless security

Use wireless intrusion prevention system (WIPS) Enable WPA-PSK Use a good passphrase (https://grc.com/password) Use WPA2 where possible AES is more secure, use TKIP for better performance Change your SSID every so often Wireless network users should use or upgrade their

network to the latest security standard released


Wireless Network tools

MAC Spoofing http://aspoof.sourceforge.net/ http://www.gorlani.com/publicprj/macmakeup/macmakeup.asp http://www.klcconsulting.net/smac/

WEP Cracking tools http://www.backtrack-linux.org/ http://www.remote-exploit.org/articles/backtrack/index.html http://wepattack.sourceforge.net/ http://wepcrack.sourceforge.net/

Wireless Analysers http://www.kismetwireless.net/ http://www.netstumbler.com/


Questions

Q1) Given the cipher-text: 11010110 and the plaintext: 00110101. Compute the keystream.

A1) cipher-text: 1 1 0 1 0 1 1 0 plain-text: 0 0 1 1 0 1 0 1 keystream: 1 1 1 0 0 0 1 1

Encrypting: plain-text keystream = cipher-text

Decrypting: cipher-text keystream = plain-text


Questions (Cont’d)

Q2) Why SSID hiding or disabling technique is not an 100% effective?

A2) The beacon broadcasting cannot be turned off and hackers can still detect the SSID by sniffing different messages using hacking tools.


Questions(Cont’d)

Q3) List 4 WEP vulnerabilities

A3) 1. The Initialization Vector (IV) is Too Small2. The Integrity Check Value (ICV) algorithm is not

appropriate3. WEP’s use of RC4 is weak4. Authentication Messages can be easily forged


REFERENCES

1. Hytnen, R., and Garcia, M. An Analysis of Wireless Security. 2006

2. Whalen, S. Analysis of WEP and RC4 Algorithms. March 20023. http://en.wikipedia.org/wiki/IEEE_802.1X4. Wireless LAN Medium Access Control and Physical Layer

Specifications. IEEE Std 802.11. June 2007 5. http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy6. http://en.wikipedia.org/wiki/Advanced_Encryption_Standard


Thank You!Questions?


5169 wireless network_security_amine_k

Documents

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temporal network

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modeinfrastructure mode

client wont