Table of Contents
Advertisement
Command Usage
• WPA enables the access point to support different unicast
encryption keys for each client. However, the global
encryption key for multicast and broadcast traffic must be
the same for all clients. This command sets the encryption
type that is supported by all clients.
• If any clients supported by the access point are not WPA
enabled, the multicast-cipher algorithm must be set to WEP.
• WEP is the first generation security protocol used to encrypt
data crossing the wireless medium using a fairly short key.
Communicating devices must use the same WEP key to
encrypt and decrypt radio signals. WEP has many security
flaws, and is not recommended for transmitting highly
sensitive data.
• TKIP provides data encryption enhancements including
per-packet key hashing (i.e., changing the encryption key
on each packet), a message integrity check, an extended
initialization vector with sequencing rules, and a re-keying
mechanism.
• TKIP defends against attacks on WEP in which the
unencrypted initialization vector in encrypted packets is
used to calculate the WEP key. TKIP changes the
encryption key on each packet, and rotates not just the
unicast keys, but the broadcast keys as well. TKIP is a
replacement for WEP that removes the predictability that
intruders relied on to determine the WEP key.
• AES has been designated by the National Institute of
Standards and Technology as the successor to the Data
Encryption Standard (DES) encryption algorithm, and will
be used by the U.S. government for encrypting all sensitive,
nonclassified information. Because of its strength, and
resistance to attack, AES is also being incorporated as part
of the 802.11 standard.
Example
AP(if-wireless g)#multicast-cipher TKIP
AP(if-wireless g)#
Wireless Interface Commands
7-115
Advertisement
Table of Contents
