06-04-2011, 10:43 AM
Presented By
SHASHANK.M
[attachment=11763]
WPA 2:WIRELESS PROTECTED ACCESS
Overview
What is WPA2?
Wi-Fi Protected Access 2
Introduced September 2004
Two Versions
Enterprise – Server Authentication 802.1x
Personal – AES Pre-Shared Key
Full implementation of 802.11i
Bit of History
802.11-1997
First wireless networking standard
Security via WEP
Wired Equivalent Privacy
WEP shown to have weaknesses in 2001 involving its use of RC4-Stream Cipher
Today it can be cracked in several minutes using standard hardware and freeware software.
Bit of History
802.11i – WPA
Draft implementation
WPA implemented a subset of 802.11i specifications.
Replaced WEP with WPA-TKIP in 2003
Most wireless cards easily upgraded via firmware
Most pre-2003 routers could not be upgraded
Weakness has been discovered
Involved TKIP algorithm use of RC4 cipher.
WPA2
802.11i – WPA2
Full implementation
Adopted in September, 2004
Replaced WPA with WPA2-AES in 2004
Backwards compatible with WPA
Uses AES-CCMP
Advanced Encryption Standard – Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (Very Strong)
Provides RSN (Robust Security Network)
Robust Security Network via 802.1X
IEEE 802.1X is the standard defined by IEEE for port based network access control.
Basically a protocol to make sure only legitimate clients can use a network secured by WPA2
Robust Security Network via 802.1X
Three players are needed to run the 802.1X protocol which uses EAP or Extensive Authentication Protocol
A client (STA/Supplicant)
A wireless access point (AP STA/Authenticator)
An authentication server (AS)
PMK – Pairwise Master Key
Sent from the AS to the Authenticator
Both the Supplicant and Authenticator now have the same PMK
PMK is permanent for the entire session
Must generate a Pairwise Transient Key for encryption of data.
Done using 4-way handshake
Robust Security Network via 802.1X
4-Way Handshake
Confirm that the client holds the PMK.
Confirm that the PMK is correct and up-to-date.
Create pairwise transient key (PTK) from the PMK.
Install the pairwise encryption and integrity keys into IEEE 802.11.
Transport the group temporal key (GTK) and GTK sequence number from Authenticator to Supplicant and install the GTK and GTK sequence number in the STA and, if not already installed, in the AP.
Confirm the cipher suite selection.
Nonce
A value that shall not be reused with a given key, including over all reinitializations of the system through all time.
Robust Security Network via 802.1X
PTK (Pairwise Transient Key – 64 bytes)
16 bytes of EAPOL-Key Confirmation Key (KCK)– Used to compute MIC on WPA EAPOL Key message
16 bytes of EAPOL-Key Encryption Key (KEK) - AP uses this key to encrypt additional data sent (in the 'Key Data' field) to the client (for example, the RSN IE or the GTK)
16 bytes of Temporal Key (TK) – Used to encrypt/decrypt Unicast data packets
8 bytes of Michael MIC Authenticator Tx Key – Used to compute MIC on unicast data packets transmitted by the AP
8 bytes of Michael MIC Authenticator Rx Key – Used to compute MIC on unicast data packets transmitted by the station
Last two only used when TKIP is used.
WPA2-PSK
Pre-Shared Key Mode
Network traffic encrypted using a 256 bit PMK
User enters key (Pairwise Master Key)
64 hex digits
8-63 Printable ASCII characters
Takes the passphrase, salts it with SSID of AP, then runs it through 4096 iterations of HMAC-SHA-1
WPA2-PSK
Authentication, Connection, Establishment of PTK and GTK.
Similar process as when an AS is present except the PSK is used as the PMK.
Creation of PTK and GTK is the same as in Enterprise mode.
Data Encryption via AES-CCMP
From PC-Mag:
(AES-Counter Mode CBC-MAC Protocol) The encryption algorithm used in the 802.11i security protocol. It uses the AES block cipher, but restricts the key length to 128 bits. AES-CCMP incorporates two sophisticated cryptographic techniques (counter mode and CBC-MAC) and adapts them to Ethernet frames to provide a robust security protocol between the mobile client and the access point.
AES itself is a very strong cipher, but counter mode makes it difficult for an eavesdropper to spot patterns, and the CBC-MAC message integrity method ensures that messages have not been tampered with.