Symantec 10521146 Administration Guide - Page 356

356 Glossary private key A part of asymmetric encryption that uses a private key in conjunction with a public key. The private key is kept secret, while the public key is sent to those with whom a user expects to communicate. The private key is then used to encrypt the data, and the corresponding public key is used to decrypt it. The risk in this system is that if either party loses the key or the key is stolen, the system is broken. probe An effort, such as a request, transaction, or program, that is used to gather information about a computer or the state of a network. For example, sending an empty message to see whether a destination actually exists. Ping is a common utility for sending such a probe. Some probes are inserted near key junctures in a network for the purpose of monitoring or collecting data about network activity. protocol A set of rules for encoding and decoding data so that messages can be exchanged between computers and so that each computer can fully understand the meaning of the messages. On the Internet, the exchange of information between different computers is made possible by the suite of protocols known as TCP/IP. Protocols can be stacked, meaning that one transmission can use two or more protocols. For example, an FTP session uses the FTP protocol to transfer files, the TCP protocol to manage connections, and the IP protocol to deliver data. Protocol Anomaly Detection One of an array of methodologies by which Symantec Network Security inspects network traffic, compares observed behavior during network protocol exchange to structured protocols, analyzes defiant behavior in context, and detects deviations from the norm. proxy server A server that acts on behalf of one or more other servers, usually for screening, firewall, or caching purposes, or a combination of these purposes. Also called a gateway. Typically, a proxy server is used within a company or enterprise to gather all Internet requests, forward them out to Internet servers, and then receive the responses and in turn forward them to the original requester within the company. public key A part of asymmetric encryption that operates in conjunction with the private key. The sender looks up the public key of the intended recipient and uses the public key to encrypt the message. The recipient then uses his or her private key, which is not made public, to decrypt the message. public key cryptography A cryptographic system in which two different keys are used for encryption and decryption. Also called asymmetric cryptography. The sender of the message looks up the public key of the intended recipient and uses the public key to encrypt the message. The recipient then uses his or her private key, which is not made public to decrypt the message. This method of encryption is considered more secure than symmetrical cryptography because one of the keys is kept strictly private. QoS (quality of service) The idea that transmission rates, error rates, and other characteristics on the Internet and in other networks, can be measured, improved, and, to some extent, guaranteed in advance. QoS is of particular concern for the continuous transmission of high-bandwidth video and multimedia information.