ZyXEL Communications Prestige 320W Support Notes page 32

P320W Support Notes
The standard does not discuss how the shared key is established. In practice, most installations use a
single key that is shared between all mobile stations and access points APs.
WEP employs the key encryption algorithm, Ron's Code 4 Pseudo Random Number Generator (RC4
PRNG). The same key is used to encrypt and decrypt the data.
WEP has defenses against this attack. To avoid encrypting two cipher texts with the same key stream, an
Initialization Vector (IV) is used to augment the shared WEP key (secret key) and produce a different
RC4 key for each packet, the IV is also included in the package. WEP key (secret key) is available in two
types, 64-bits and 128-bits. Many times you will see them referenced as 40-bits and 104-bits instead. The
reason for this misnomer is that the WEP key ( 40/104 bits ) is concatenated with the initialization vector
( 24 bits ) resulting in a 64/128 bit total key size.
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