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Appendix F: Glossary

96 Cobalt CacheRaQ 4 User Manual

Secure Sockets Layer (SSL)

Secure Sockets Layer is a program layer created by Netscape

Communications for managing the security of message transmissions in a

network. Netscape’s idea was that the programming for keeping your

messages conﬁdential ought to be contained in a program layer between

higher-level protocols (such as HTTP or IMAP) and the TCP/IP layers of the

Internet. The “sockets” part of the term refers to the sockets method of

passing data between a client and a server program in a network or between

program layers in the same computer.

SSL allows an SSL-enabled server to authenticate itself to an SSL-enabled

client, allows the client to authenticate itself to the server, and allows both

machines to establish an encrypted connection.

These capabilities address fundamental concerns about communication over

the Internet and other TCP/IP networks:

• SSL server authentication allows a user to confirm the identity of a

server. SSL-enabled client software can use standard techniques of

public-key cryptography to check that a server’s certificate and public ID

are valid and have been issued by a certificate authority (CA) listed in the

client’s list of trusted CAs. This confirmation can be important if, for

example, the user is sending a credit card number over the network and

wants to check the receiving server’s identity.

• SSL client authentication allows a server to confirm a user’s identity.

Using the same techniques as those used for server authentication, SSL-

enabled server software can check that a client’s certificate and public ID

are valid and have been issued by a certificate authority (CA) listed in the

server’s list of trusted CAs. This confirmation can be important if, for

example, the server is a bank sending confidential financial information

to a customer and wants to check the recipient’s identity.

• an encrypted SSL connection requires all information sent between a

client and a server to be encrypted by the sending software and decrypted

by the receiving software, thus providing a high degree of

confidentiality. Confidentiality is important for both parties to any

private transaction. In addition, all data sent over an encrypted SSL

connection is protected with a mechanism for detecting tampering —

that is, for automatically determining whether the data has been altered

in transit.