WEP MPDU (MAC Protocol Data Unit) Format

The WEP MPDU (MAC Protocol Data Unit) Format is shown below Key ID (2) bits – used to select the WEP key index – when Key-mapping keys are used the Key Id field is ignored IV – initialization vector ICV – integrity check value – calculated over the MPDU plaintext data The WEP encapsulation and […]

WEP Decapsulation

The WEP decapsulation is pictorially depicted below FIG Courtesy: 802.11 Standard WEP follows the below procedure to decrypt the received 802.11 WEP encrypted frame. WEP extracts the initialization vector (IV) and Key ID from the received packet to obtain the relevant WEP key. If Key-mapping keys are used, then the Key-mapping key will be used […]

Beacon Frame format

The Beacon Frame format is as provided below: FIG Courtesy: 802.11 Wireless Networks: The Definitive Guide, 2nd Edition As can be seen from the pictorial representation above – the beacon frame consists of mandatory fields and optional fields. The Mandatory fields are those fields that are required for the proper working of the network. Optional […]

WEP Encapsulation

The WEP Encapsulation is shown pictorially below Fig Courtesy: 802.11 Standard The WEP encryption algorithm is ARC4 stream cipher provided by RSA Security Inc. The ARC4 cipher uses a pseudo-random number generator (PRNG) to generate a key-stream. This Key-stream is exclusive OR’ed with the plain text data to obtain the encrypted text. The exclusive OR […]

Traffic Indication Map Explained

Traffic Indication Map (TIM) is an Information element and is part of the Beacon frame that is sent out by the Access Point at regular intervals. The TIM Information element provides information on the current DTIM count and DTIM period and also provides information on whether Buffered Multicast/Broadcast Data or unicast data for different 802.11 […]

Problems in WEP Encryption

In a wired network – due to the fact that stations are connected via cables, the data is pretty secure in itself. However when the transmission medium is air, all data transmissions are heard by every Station in the network. The Data can also be sniffed by hacker stations that can try and decrypt the […]

802.1X Authentication and Data Security enhancements

The initial Open system authentication and Shared Key authentication provided for user authentication by the 802.11 standard body was seen to be inadequate in providing a strong user authentication method. To circumvent the issues seen in the 802.11 authentication methods, the decision to use upper layer authentication of user stations was considered. The use of […]

802.1X Authentication – Generation of Master Key

The 802.1X authentication mechanism is an upper layer authentication mechanism and comprises of a supplicant (802.11 Station), Authenticator (Access Point) and Authentication Server (e.g. RADIUS). Numerous methods of upper layer authentication are specified in various RFCs. Some examples are provided be below EAP-TLS EAP-TTLS EAP-GTC PEAP-MSCHAPv2 LEAP etc The 802.1X mechanism involves the following steps […]

WLAN Association for 802.1X/Pre-shared Key Mechanism

Prior to the 802.1 X EAP and 4-way EAPOL handshakes – the 802.11 Station and the Access Point exchange information to associate to one another. At the end of a successful association – the 802.11 client is connected to the Access point but the Data channel is still blocked. The Data channel will be enabled […]