In contrast to Open System Authentication, in Shared Key Authentication the key that would be used for data security is used to authenticate the WLAN station. The Below steps are followed in Shared Key Authentication Authentication request sent by WLAN (802.11) STA to Access Point AP sends a challenge text to 802.11 STA (in cleartext) […]
WEP Encryption – Key Mapping Keys
A Key-Mapping Key is a key which maps to a Transmitter address – Receiver address combination. That is, The Key-mapping key between a particular transmitter address and a receiver address can only be used between that [transmitter address, receiver address] combination and not with other transmitter or receiver address combinations. This is different from that […]
WEP Encryption
The 802.11 standard introduced the WEP (wired Equivalent Privacy) in the very first 802.11 standard as a means of providing security for WLAN packet transmissions. The WEP security as the name suggests was supposed to provide frame protection equivalent to a Wired Network. The WEP Encryption method provided two types of Encryption keys Default WEP […]
WPA Information Element
The Wi-Fi/802.11 standard introduced two new Information elements to cater to the new WPA/WPA2 encryption scheme. They are the WPA (Wireless Protected Access) and RSN (Robust Security Network) Information Elements. Any Station containing a WPA/RSN information element in its Association request would need to perform an 802.11i/802.1X security handshake. The WPA Information Element is shown […]
Understanding WPA and WPA2
WPA stands for Wireless Protected Access. The WPA standard was introduced by the Wi-Fi Alliance. The WPA standard introduced TKIP (Temporal Key integrity Protocol) as an advancement on WEP to provide better security. WPA also introduced upper layer user authentication for 802.11 devices. Two methods for user authentication were described Pre-shared Key (EAPOL Handshake) 802.1X […]
AES Decapsulation
For reference – the interested reader can look at AES Encyption frame format and the AES Encapsulation process in the below articles AES Encryption Mechanism AES Encapsulation The AES decapsulation process is shown below FIG Courtesy: 802.11 Standard Some description of the parameters TK – AES Temporal Key – obtained during EAPOL handshake PN – […]
Distributed Co-ordination Function
DCF or Distributed Co-ordination Function was the initial Access mechanism introduced by the 802.11 standard’s body. The mechanism defined how different 802.11 stations need to compete in order to gain access to the transmission (air) medium for transmitting a packet. The DCF mechanism is a carrier sense multiple access and collision avoidance (CSMA/CA) mechanism and […]
Back-off Mechanism in WLAN
An example Back-off mechanism is depicted pictorially below FIG COURTESY: IEEE Std 802.11-2012TM (section 9.3.4.3) The figure depicts 5 802.11 stations trying to compete for the air medium using DCF mechanism Station A has the transmitting right at the beginning – all the other stations back-off for the duration of transmission by Station A and […]
EDCA (WMM) information Elements – Part 1
The EDCA Parameter Set Information Element provides the access category information to the WLAN station. The EDCA Parameter set is not used widely in the real world but the WMM Parameter set element is used instead. The reason for the use of the WMM Parameter set element is that the WMM standard was ratified and […]
DCF Timing Relationships
The below diagram depicts the timing relations for different time intervals in DCF FIG Courtesy : 802.11 Standard Point Coordination Function (PCF)