In cryptography , a cipher (or cypher ) is an algorithm for performing encryption or decryption .
4 wifi security
Wireless Network Security
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 Mbps@2.4 GHz Full speed up to 300 feet Coverage up to 1750 feet Cisco products: Aironet 340, 350, 1100, 1200 802.11g – 54 Mbps@2.4 GHz Same range as 802.11b Backward-compatible with 802.11b Speeds slower in dual-mode Cisco products: Aironet 1100, 1200 Wireless Network Security
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 Security
Wireless Network Modes The 802.11 wireless networks operate in two basic modes: 1. Infrastructure mode 2. 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 Security
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 Wireless Network Security
Security Threats• Wireless technology doesn’t remove any old security issues, but introduces new ones – Viruses, Trojans and stuff like that are still there – Eavesdropping – Man-in-the-middle attacks – Denial of Service
Eavesdropping (Sniffing)• Easy to perform, almost impossible to detect• By default, everything is transmitted in clear text – Usernames, passwords, content ... – No security offered by the transmission medium• Different tools available on the internet – Network sniffers, protocol analysers . . .• With the right equipment, it’s possible to eavesdrop traffic from few kilometers away
Wireless Man in the Middle (MITM) Attack In a MITM attack, the attacker funnels victim’s traffic through apoint controlled by the attacker. Allows data analysis andmanipulation1. Attacker spoofes a disassociate message from the victim2. The victim starts to look for a new access point, and the attacker advertises his own AP on a different channel, using the real AP’s MAC address3. The attacker connects to the real AP using victim’s MAC address
Denial of Service• Frequency jamming – Not very technical, but works• Spoofed deauthentication / disassociation messages – can target one specific user• Attacks on higher levels – SYN Flooding – Ping of death – ...
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. 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 Wireless Network Security 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) Wireless Network Security
WEP - Wired Equivalent Privacy The original native security mechanism for WLAN Used to protect wireless communication from eavesdropping (()التنصتconfidentiality) Prevent unauthorized access to a wireless network (access control) Prevent tampering with transmitted messages (integrity) Provide users with the equivalent level of privacy inbuilt in wireless networks. Wireless Network Security
WEP1. 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) 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. The key stream is then used to convert the plain text message into the WEP encrypted frame. Initialization Vector IV Dynamic 24-bit value Chosen randomly by the transmitter wireless network interface 16.7 million possible keys (224)
WEP Authentication1. The station sends an authentication request to AP2. AP sends challenge text called nonce to the station.3. The station uses its configured 64-bit or 128-bit default key to encrypt the nonce, and it sends the latter to AP.4. AP decrypts the encrypted nonce using its configured WEP key that corresponds to the stations default key.5. AP compares the decrypted nonce with the original nonce.6. If the decrypted nonce matches the original nonce, 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 problemsPlaintext attack• Attacker sniffs nonce (challenge), m, sent by AP• Attacker sniffs response sent by station: – IV in clear – Encrypted nonce, c• Attacker calculates keystream ks = m ⊕ c, which is the keystream for the IV .• Attacker then requests access to channel, receives nonce m’• Attacker forms response c’ = ks ⊕ m’ and IV• Server decrypts, matches m’ and declares attacker authenticated ! 17
WEP flaws and vulnerabilities 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. With IV reuse, it is possible to determine keystreams and hence enable an attacker to forge packets obtaining access to the WLAN. Wireless Network Security
Attacks on WEPWEP encrypted networks can be cracked in 10 minutesGoal is to collect enough IVs to be able to crack the keyIV = Initialization Vector, plaintext appended to the key toavoid RepetitionInjecting packets generates IVs Wireless Network Security
Attacks on WEP Backtrack 5 (Released 1st March 2012) Tutorial is available All required tools on a Linux bootable CD + laptop + wireless card Wireless Network Security
WEP cracking example Wireless Network Security
WPA – (WI-FI Protected Access) New technique in 2002. Overcomes the security flaws of WEP. Improved data encryption – Data is encrypted using the RC4 stream cipher, with a 128-bit key and a 48-bit initialization vector (IV). 248 is a large number! More than 500 trillion Because of many attacks related to static key in WEP, WPA uses a Temporal Key Integrity Protocol (TKIP), which dynamically changes keys as the system is used. This combined with the much larger IV, defeats the well-known key recovery attacks on WEP. A more secure message authentication code (usually known as a MAC, but here termed as MIC for "Message Integrity Code") is used in WPA, an algorithm named "Michael".
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 Wireless Network Security
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 ( http://wirelessdefence.org/Contents/coWPAttyMain.htm ) 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) Wireless Network Security
WPA Cracking Example Wireless Network Security
Techniques to improve wireless security Use wireless intrusion prevention system (WIPS) Enable WPA-PSK Use a good password (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 released security standard
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