The Wired Equivalency Privacy algorithm (WEP) of the 802.11 Wireless LAN Standard uses which of
the following to protect the confidentiality of information being transmitted on the LAN?
A.
A digital signature that is sent between a mobile station (e.g., a laptop with a wireless Ethernet
card) and a base station access point
B.
A public/private key pair that is shared between a mobile station (e.g., a laptop with a wireless
Ethernet card) and a base station access point
C.
A secret key that is shared between a mobile station (e.g., a laptop with a wireless Ethernet card)
and a base station access point
D.
Frequency shift keying (FSK) of the message that is sent between a mobile station (e.g., a laptop
with a wireless Ethernet card) and a base station access point
Explanation:
The transmitted packets are encrypted with a secret key and an Integrity Check (IC) field comprised
of a CRC-32 check sum that is attached to the message. WEP uses the RC4 variable key-size stream
cipher encryption algorithm. RC4 was developed in 1987 by Ron Rivest and operates in output
feedback mode. Researchers at the University of California at Berkely (wep@isaac.cs.berkeley.edu)
have found that the security of the WEP algorithm can be compromised, particularly with the
following attacks: Passive attacks to decrypt traffic based on statistical analysis Active attack to inject
new traffic from unauthorized mobile stations, based on known plaintext Active attacks to decrypt
traffic, based on tricking the access point Dictionary-building attack that, after analysis of about a
day’s worth of traffic, allows real-time automated decryption of all traffic The Berkeley researchers
have found that these attacks are effective against both the 40-bit and the so-called 128-bit versions
of WEP using inexpensive off-the-shelf equipment. These attacks can also be used against networks
that use the 802.11b Standard, which is the extension to 802.11 to support higher data rates, but
does not change the WEP algorithm. The weaknesses in WEP and 802.11 are being addressed by the
IEEE 802.11i Working Group. WEP will be upgraded to WEP2 with the following proposed changes:
Modifying the method of creating the initialization vector (IV) Modifying the method of creating the
encryption key Protection against replays Protection against IV collision attacks Protection against
forged packets In the longer term, it is expected that the Advanced Encryption Standard (AES) will
replace the RC4 encryption algorithm currently used in WEP.