Enhancing Wireless Security with WPAAgendaOverview of WLANSecurity Mechanism – Wired Equivalent PrivacyWEP EncryptionWEP AuthenticationWEP WeaknessesPromise of WPA - Wireless Protected AccessWPA - Modes of OperationEnterprise Mode DiagramPSK Mode DiagramIssues of PSK ModeSecurity Mechanisms in WPA802.1X Authentication prevents end users from accessing Enterprise networksSimpler RepresentationMutual AuthenticationTKIP – Temporal Key Integrity ProtocolTKIP for Data PrivacyMichael Message Integrity CheckWEP vs. WPADrawbacks of WPAUpcoming WPA2Encryption Method Comparison TableConclusionsReferencesSlide 261Enhancing Wireless Security with WPACS-265 ProjectSection: 2 (11:30 – 12:20)Shefali JariwalaStudent ID0017906602AgendaOverview of WLAN WEP and its weaknessesPromise of WPA- Modes of Operations- Security MechanismsWhat is WPA2?Encryption Method Comparison TableConclusions3WLAN Standards• 802.11 1-2 Mbps speed 2.4 GHz band• 802.11a (Wi-Fi) 54 Mbps speed 5 GHz band• 802.11b (Wi-Fi) 11 Mbps speed 2.4 GHz band• 802.11g (Wi-Fi) 54 Mbps speed 2.4 GHz bandWLAN components• Wireless Clients• Access PointsRequirements for secure WLAN• Encryption and Data Privacy• Authentication and Access ControlOverview of WLAN4Security Mechanism – Wired Equivalent Privacy• Confidentiality, Access Control and Data Integrity• Both WEP Authentication and encryption are based on a secret key shared between AP and wireless client• WEP uses RC4 encryption algorithm Symmetric Key stream Cipher variable length key 64 bit = 40 bit WEP key and 24 bit random number known as IV to encrypt the data Encryption: stream cipher plaintext = cipher text Sender sends the packet = cipher text + IV to receiver Decryption: WEP key and attached IV5WEP EncryptionWLAN security: Current and Future, Park, J.S; Dicoi, D.; IEEE Internet Computing, Volume:7, Issue:5, Sept-Oct, 2003, 60-656 Two modes of authentication: Open System ( “No Authentication”) Shared KeyWEP AuthenticationClient Access Point Authentication request Random challenge Encrypted RC Success/failure response7 A single key is used for all AP’s and wireless clients Static WEP key ~ Dynamic WEP Key Same key used for Access Control and Encryption which gives rise to problems Initialization Vector (IV) Reuse Ci = Pi ksi and Ci’= Pi’ ksi’ Therefore, Ci Ci’= Pi Pi’ Known Plain text attacks WEP provides no replay protection When WEP was available it was not always turned onWEP Weaknesses8 stronger security solution via standards-based interoperable security specification known as WPA (Wi-Fi specification) WPA is a subset of 802.11i standard and maintains forward compatibility Run as software upgrade on AP’s and NIC’s and minimizes the impact of network performance Inexpensive in terms of cost/time to implement and addresses all WEP weaknesses Secure all versions of 802.11 devices including 802.11b, 802.11a and 802.11g Promise of WPA - Wireless Protected Access9 Enterprise Mode: - Requires an authentication server – RADIUS (Remote Authentication Dial In Service) for authentication and key distribution- RADIUS has centralized management of user credentials Pre-shared key (PSK) Mode: - Does not require authentication server- A “shared secret” is used for authentication to access point- vulnerable to dictionary attacksWPA - Modes of Operation10Enterprise Mode Diagramhttp://www.wi-fi.org/opensection/pdf/whitepaper_wi-fi_security4-29-03.pdf11PSK Mode Diagram http://www.wi-fi.org/opensection/pdf/whitepaper_wi-fi_security4-29-03.pdf12 Needed if no authentication server is in use “shared secret” – revealed, network security is compromised No standardized way of changing shared secret It increases the attacker’s effort to do decryption of messages The more complex the shared secret is, the better it is as there are less chances of dictionary attacksIssues of PSK Mode13Security Mechanisms in WPAhttp://www.intel.com/ebusiness/pdf/wireless/intel/wpa_cmt_security.pdf14802.1X Authentication prevents end users from accessing Enterprise networkshttp://www.mtghouse.com/MDC_WP_052603.pdf15Simpler RepresentationAuthenticator(Access Point)Initiates connectionSupplicant(Wireless Client)Port = enabledState = unauthorizedrequests identityresponds with identityResponse ACCEPT/REJECTSupplicant’sPort = enabledState = authorizedForwards the identityForwards Responserequests identity from RADIUSForwards the requestRADIUS passes its identityAccess points forwards the identity RADIUS16Mutual Authenticationhttp://www.mtghouse.com/MDC_WP_052603.pdf17 TKIP is responsible for generating the encryption key, encrypting the message and verifying its integrity TKIP ensures: - Encryption key changes with every packet - Encryption key is unique for every client - TKIP encryptions keys are 256 bit long WEP Encryption key = shared secret + IV TKIP packet comprises of: - 128 bit temporal key (shared by both clients and AP) - Client Device MAC address - 48 bit IV (Packet sequence number) to prevent known plain text attacks (WEP = 24 bit IV) TKIP – Temporal Key Integrity Protocol18 TKIP key mixing function + temporal key = per packet key Temporal keys - 128 bit, change frequently, definite life MAC Address + Temporal key + four most significant octets of the packet sequence number are fed into the S-Box to generate intermediate key Results in a unique encryption key Then, mix the intermediate key with two least significant octets of packet sequence number = 128 bit per packet key Each key encrypts only one packet of data and prevents weak key attacksTKIP for Data Privacy19 Used to enforce data integrity “Message Integrity Code” (MIC) = 64 bit message calc. using Michael’s algorithm MIC is inserted in the TKIP packet The sender and the receiver each compute MIC and then compare. MIC does not match = data is manipulated Detects potential packet content altercation due to transmission error or purposeful manipulation Uses 64 bit key and partitions the data into 32 bit blocks Various operations: shifts, XOR’s, additions Michael Message Integrity Check20WEP vs.
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