Mobile and Wireless Communication Security By Jason Gratto

WEP (Wired Equivalent Privacy) Intended to provide confidentiality Key size:40 bits Key distribution: Manual Meant to protect wireless communication from eavesdropping Also meant to prevent unauthorized access to wireless network

Goals of WEP Access Control Data Integrity Confidentiality

Protocol of WEP Uses a secret key between the computer and the access point – The secret key is used to encrypt the packets – No standard for sharing the key but in practice a single key is shared between all of the computers and access points.

WEP - Procedure Generates a checksum Generates a keystream with a chosen IV (Initialization Vector) v with RC4 XOR between message/checksum and the keystring Transmits the v and the ciphertext

WEP – Procedure

WEP - Defenses Integrity Check (IC) – Used to ensure packet wasn’t modified in transit Initialization Vector (IV) – Used to avoid encrypting two ciphertexts with the same key stream – Used to augment the shared key and produce a different RC4 for each packet

WEP – Vulnerabilities ICV insecure – ICV is a algorithm for creating the checksum, based on CRC32 and can be modified to match the contents of the message. IV key reuse – Because a small IV value is used, IV values end up being reused, compromising the security. Authentication forging – Using a recovered key stream and IV the authentication can be forged.

WEP – Attack types Passive – Eavesdropping on wireless traffic Active – Constructing it’s own encrypted packets when plaintext is known Active from both sides – Constructing it’s own encrypted packets when only header is known by guessing. Dictionary building – Computing the key stream using a decryption table

Wi-Fi Protected Access (WPA) Key size: 128 bits Hash method: ICV, MICHAEL Key distribution: TKIP (Temporal Key Integral Protocol) Inclusion of EAP certification for enterprise versions of WPA

MICHAEL MICHAEL generates a MIC (Message Integrity Code) – 8 bits long – Placed between the data and the ICV

TKIP Made to address security problems with WEP Looks to client’s configuration to determine what kind of key to use Sets a unique default key for each client

TKIP - Defenses Implements a key mixing function that combines a secret key with an IV before performing RC4 initialization If packets are received out of order, they are rejected by the access point Implements the MICHAEL integrity check to prevent forged packets from being accepted

Extensible Authentication Protocol (EAP) Is a transmission method and framework for authentication protocols – Works with many other authentication protocols such as RADIUS and Kerberos Uses a variety of different transport methods

EAP Originally designed for wired connections – To be used in a wireless environment, the “tunneled” EAP method was created, wrapping the EAP in a stronger encrypted EAP Common transport methods – EAP-TLS (Transport Layer Security) – EAP-TTLS (Tunneled Transport Layer Security) – PEAP (Protected EAP) – LEAP (Light EAP)

EAP Types PEAP – Interior MSCHAPv2 inside a secure TLS tunnel EAP-TTLS – Interior EAP-MD5 inside a secure TLS tunnel LEAP – Modified version of MSCHAP – Vulnerable to dictionary attacks

WPA –Vulnerabilities Denial of Service – Any time forged and unauthorized data is detected, it shuts the access point down for 60 seconds Because of this it is easy to shut down access points using little network activity

WPA2 Updated version of WPA Uses AES encryption and allows use of RADIUS (Remote Authentication Dial In User Service) authentication protocol

RADIUS Protocol for communication between Network Access Server (NAS) and a remote authentication server Requires clients and servers

RADIUS Data needed for authenticaiton – User data IP Name or address Shared secret key – User information Username and password – Session information Speed, port, NAS ID

RADIUS – Database The database can be stored in a number of different ways – A text file – Password file – Netware directory The database can authenticate in a number of ways as well – Username/password – SecurID Token Card

RADIUS After authentication is requested, the RADIUS server either accepts or rejects the NAS based on the following – Session timers – Filters – IP Address – IDSN Session Parameters

RADIUS ISP User Database ISP Modem Pool User dials modem pool and establishes connection UserID: bob Password: ge55gep UserID: bob Password: ge55gep NAS-ID: Select UserID=bob Bob password=ge55gep Timeout=3600 [other attributes] Access-Accept User-Name=bob [other attributes] Framed-Address= The Internet ISP RADIUS Server Internet PPP connection established ISP User Database ISP Modem Pool User dials modem pool and establishes connection UserID: bob Password: ge55gep UserID: bob Password: ge55gep NAS-ID: Select UserID=bob Bob password=ge55gep Timeout=3600 [other attributes] Access-Accept User-Name=bob [other attributes] Framed-Address= The Internet ISP RADIUS Server Internet PPP connection established

Sources /cubukcu.pdf /cubukcu.pdf eport/Kalina.ppt eport/Kalina.ppt u/pdfs/Wireless_EAP.pdf u/pdfs/Wireless_EAP.pdf chard/2-radius/index.htm