Wired Equivalent Privacy (WEP) is the RC4-based algorithm specified in Clause 11.2.2 of the IEEE 802.11-2012 standard and Clause 8.2 of the 802.11i-2004 standard.
The WEP cipher uses a 40- or 104-bit key. If the miniport driver supports the Extensible Station (ExtSTA) mode, the 802.11 station can support a WEP key larger than 104 bits. The miniport driver reports the maximum size of the WEP key supported by the 802.11 station when OID_DOT11_EXTSTA_CAPABILITY is queried.
WEP keys can be statically defined on the 802.11 station or dynamically defined through a port-based authentication algorithm, such as IEEE 802.1X.
The 802.11 station uses the following key types for WEP cipher operations:
The following figure illustrates the format of the 802.11 MAC protocol data unit (MPDU) frame encrypted through the WEP algorithm.
The WEP-encrypted MPDU frame consists of the following:
- Initialization Vector (IV)
A unique 24-bit value combined with the WEP key identified by the Key ID field to form the key used in the RC4 cipher algorithm. If a key-mapping key exists for the receiver address (RA) and transmitter address (TA), the 802.11 station combines the IV value with the key-mapping key to form the RC4 key.
- Key Identifier (ID)
Bits 7 through 6 store the index of the key, within the default key table, used to form the RC4 key. The 802.11 station ignores this field if a key-mapping key exists for the RA/TA pair. Bits 5 through 0 are reserved and set to zero.
- Payload Data
Data from the MAC service data unit (MSDU) packet.
- Integrity Check Value (ICV)
The checksum value computed over the unencrypted payload data.
- Frame Check Sequence (FCS)
The IEEE 32-bit cyclic redundancy code (CRC) computed over all fields of the MPDU.