Certificate authority. Network software that issues and manages security credentials and public keys for authentication and message encryption. As part of a public key infrastructure (PKI), which enables secure exchanges of information over a network, a certificate authority checks with a registration authority (RA) to verify information provided by the requestor of a digital certificate. If the registration authority verifies the requestor's information, the certificate authority can issue a certificate. Based on the PKI implementation, the certificate content can include the certificate's expiration date, the owner's public key, the owner's name, and other information about the public key owner. See also RA.
CCMP
Counter-Mode Cipher Block Chaining Message Authentication Code Protocol. CCMP is the AES-based encryption protocol defined in 802.11i. CCMP is a symmetric key block cipher mode encryption protocol.
certificate
A generic term used to describe a digital signature of a device. Certificates are used to generate keys used in a PKI (public key infrastructure) environment.
certificate authority
See CA.
channel
A frequency band in which a specific broadcast signal is transmitted.
CHAP
Challenge Handshake Authentication Protocol. An authentication scheme that uses a three-way handshake (challenge, response, verify) to authenticate the identity of the peer. CHAP is defined in RFC 1334. The client responds to the server's challenge message, which in turn verifies the response by comparing it to the expected value. If it is successfully verified, the client is authenticated.
CLI
Command-line interface. The command-line interface is a nongraphical method of managing a network device, such as an access point. IOS is an example of a CLI-based solution. Note that many CLI interfaces also provide more user-friendly graphical user interfaces (GUI). Also known as "command line" and "command prompt."
client
In a WLAN, a client is any device with a radio interface that does not act as a pass-through or relay.
collision
The result of two or more stations attempting to transmit a packet across the network at the same time, when the network uses a shared medium. Because wireless networks use a shared medium or single segment per access point, collisions can occur quite regularly. WLANs use a technique called CSMA/ CA to reduce such collisions because they can result in packet loss and can negatively impact the performance of the network.
command-line interface
See CLI.
CRC
Cyclic redundancy check. A simple method of checking message integrity.
CRL
Certificate Revocation List. A list of certificates that have been revoked by the certificate authority (CA). A CRL is analogous to a "blacklist" of certificates that are no longer permitted or accepted.
cryptography
The ISO defines cryptography as "[the] discipline which embodies principles, means, and methods for the transformation of data in order to hide its information content, prevent its undetected modification, and/or prevent its unauthorized use." [ISO 7498-2: 1989]
CSMA/CA
Carrier sense multiple access with collision avoidance. The mechanism used by WLANs to reduce and detect packet collisions within cells. If a collision is detected, the station retransmits later based upon an exponential random back-off algorithm.
