5169 Wireless Network Security AmineK

7/29/2019 5169 Wireless Network Security AmineK

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Wireless Networks and Mobile Computing (CSI 5169)

Wireless Network Security

Amine Khalife

[email protected]


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Outline

1. Wireless intro & history

2. Wireless network modes

3. SSID

4. WEP

5. WPA

6. WPA2

7. Wireless Network tools

8. References



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Background & Overview History

Developed for military use Security widely noticed after Peter Shipleys 2001 DefConpreso 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



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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



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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



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Wireless Network Modes

The 802.11 wireless networks operate in two basicmodes:

1. Infrastructure mode

2. Ad-hocmode

Infrastructure mode:

each wireless client connects directly to a centraldevice called Access Point (AP)

no direct connection between wireless clients

AP acts as a wireless hub that performs theconnections and handles them between wirelessclients



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Wireless Network Modes (contd)

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 authenticationlist



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SSID Service Set Identification

Identifies a particular wireless network

A client must set the same SSID as the one in thatparticular AP Point to join the network

Without SSID, the client wont be able to select and joina wireless network

Hiding SSID is not a security measure because thewireless network in this case is not invisible

It can be defeated by intruders by sniffing it from anyprobe signal containing it.



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SSID (Contd)

A way for vendors to make more money

So easy to find the ID for a hidden network becausethe beacon broadcasting cannot be turned off

Simply use a utility to show all the current networks:

inSSIDer

NetStumbler

Kismet



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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 Wont protect each wireless client nor the traffic

confidentiality and integrity ===>vulnerable

Defeated by MAC spoofing:

ifconfig eth0 hw ether00:01:02:03:04:05 (Linux)

SMAC - KLC Consulting (Windows)

MAC Makeup - H&C Works (Windows)



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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 (accesscontrol)

Prevent tampering with transmitted messages

Provide users with the equivalent level of privacy inbuilt inwireless networks.



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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 IVrandom initialization vector (CONFIDENTIALITY).

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

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



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Encrypted WEP frame



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RC4 keystream XORed with plaintext



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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



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WEP Components (contd)

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.

2. 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 Xored

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



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WEP Components (contd)

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

XOR operation denoted as

plain-text keystream= cipher-text

cipher-text keystream= plain-text

plain-text cipher-text= keystream



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How WEP works


IV

RC4key

IV encrypted packet

original unencrypted packet checksum


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Encryption Process



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Decryption Process



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WEP Authentication

1. The station sends an authentication request to AP

2. AP sends challenge text to the station.

3. The station uses its configured 64-bit or 128-bit default key toencrypt 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, thenthe access point and the station share the same WEP key, and

the access point authenticates the station.7. The station connects to the network.



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WEP Authentication (Contd)



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WEP Authentication (Contd)

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

The authentication process leaks information aboutthe 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 thechallenge 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



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WEP flaws and vulnerabilities

Weak keys:

It allows an attacker to discover the default keybeing used by the Access Point and client stations

This enables an attacker to decrypt all messagesbeing 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, ifthe default key has not been changed and the

original message can be retrieved relatively easily.



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WEP flaws and vulnerabilities (contd)

With IV reuse, it is possible to determine keystreamsand hence enable an attacker to forge packetsobtaining access to the WLAN.

If WEP is using 40 bit long key then it will need moreprotection from attacks as compared to 128 bit long

WEP key. Hence, both are very weak and unable toprovide 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



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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 toavoid Repetition

Injecting packets generates IVs


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Attacks on WEP

Backtrack 5 (Released 1st March 2012)

Tutorial is available

All required tools on a Linux

bootable CD + laptop +

wireless card



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WEP cracking example



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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, WPAminimize shared secret key in accordance with theframe transmission.

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

data.



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WPA

Data is encrypted using the RC4 stream cipher, with a128-bit key and a 48-bit initialization vector (IV).

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

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

WPA also provides vastly improved payload integrity.



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WPA

A more secure message authentication code (usuallyknown as a MAC, but here termed a MIC for "MessageIntegrity 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 wouldstill work with most older network cards.

WPA includes a special countermeasure mechanism thatdetects an attempt to break TKIP and temporarily

blocks communications with the attacker.



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WPA



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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 trillion

Sequencing rules specify how IVs are selected andverified

2. A Message Integrity Code (MIC) called MichaelDesigned for deployed hardware

Requires use of active countermeasures

3. Key Derivation and Distribution

Initial random number exchanges defeat man-in-the-middle attacks

4. Temporal Key Integrity Protocol generates per-packet keys



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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 theAES (Advanced Encryption Standard) algorithm

The encryption in WPA2 is done by utilizing eitherAES 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



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WPA2

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

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

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



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WPA2

WPA2 has immunity against many types of hackerattacks

Man-in-the middle

Authentication forging

Replay

Key collision

Weak keys

Packet forging

Dictionary attacks



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WPA2 weaknesses

Cant protect against layer session hijacking

Cant stand in front of the physical layer attacks:

RF jamming Data flooding

Access points failure

Vulnerable to the Mac addresses spoofing



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Am I secure if I use WPA-PSK

WPA-PSK protected networks are vulnerable to dictionaryattacks

Works with WPA & WPA2 (802.11i)

New attack techniques have increased the speed of this attackCowPatty 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)



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WPA Cracking Example



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WEP vs WPA vs WPA2


WEP WPA WPA2ENCRYPTION RC4 RC4 AES

KEY ROTATION NONE DynamicSession Keys Dynamic SessionKeys

KEY

DISTRIBUTIONManually typed

into each deviceAutomatic

distribution

availableAutomatic

distribution

availableAUTHENTICATION Uses WEP key as

AuthenticationCan use 802.1x

& EAPCan use 802.1x

& EAP


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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 theirnetwork to the latest security standard released



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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/



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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



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Questions (Contd)

Q2) Why SSID hiding or disabling technique is not an100% effective?

A2) The beacon broadcasting cannot be turned off andhackers can still detect the SSID by sniffing differentmessages using hacking tools.



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Questions(Contd)

Q3) List 4 WEP vulnerabilities

A3)

1. The Initialization Vector (IV) is Too Small

2. The Integrity Check Value (ICV) algorithm is notappropriate

3. WEPs use of RC4 is weak

4. Authentication Messages can be easily forged



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REFERENCES

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

2. Whalen, S.Analysis of WEP and RC4 Algorithms. March 2002

3. http://en.wikipedia.org/wiki/IEEE_802.1X

4. Wireless LAN Medium Access Control and Physical LayerSpecifications. IEEE Std 802.11. June 2007

5. http://en.wikipedia.org/wiki/Wired_Equivalent_Privacy

6. http://en.wikipedia.org/wiki/Advanced_Encryption_Standard



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Thank You!Questions?


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5169 Wireless Network Security AmineK