Installation guide

Chapter 9
86 Sniffer Technologies
they mean the same thing, the Sniffer software supports both 40-bit and
64-bit encryption.
128-Bit Encryption
Although the usage of 128-bit encryption keys is not specified by the 802.11b
standard, most vendors implement 128-bit encryption similarly to 64-bit
encryption.
In a network using 128-bit encryption, each station on the network is
programmed with the same four 104-bit shared keys. When a station has
encrypted data to send, it generates a random 24-bit Initialization Vector (IV)
and encrypts the data to be sent with the 24-bit IV and one of its four 104-bit
shared keys. Therefore, the entire key length is 128 bits (104-bit shared key
plus a 24-bit IV).
Stations send the 24-bit IV in the clear along with the encrypted data. A header
field tells the receiving station which of the four shared keys is in use for the
encrypted data. Receiving stations use the received 24-bit IV and their own
stored 104-bit keys to decrypt the received data.
Configuring Encryption Options
You can specify the encryption keys that allow the Sniffer software to perform
WEP decryption in either Hex or ASCII format, depending on how you set the
WEP Key Entry Mode option in the 802.11 tab. Separate procedures are
provided for each mode. See Entering Encryption Keys in Hex Format on page
86 and Entering Encryption Keys in ASCII Format on page 88.
Entering Encryption Keys in Hex Format
To enter WEP encryption keys in Hex format:
1 Display the Tools > Options > 802.11 tab.
2 Select Hex for the WEP Key Entry Mode option at the bottom of the
802.11 tab.
If you have previously entered encryption keys in ASCII mode, the
Sniffer software automatically converts your entries to Hex mode. Key
entries of five ASCII characters appear as 40-bit keys in Hex mode.
Similarly, key entries of 13 ASCII characters appear as 128-bit keys in
Hex mode.
3 You can enter up to four separate encryption keys. For each key, do the
following: