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 anIntegrity 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.