SSL security services

SSL provides the following security services:

• Privacy—SSL uses a symmetric encryption algorithm to encrypt data. It uses the asymmetric key algorithm of RSA to encrypt the key used by the symmetric encryption algorithm. For more information about RSA, see "Managing public keys."

• Authentication—SSL uses certificate-based digital signatures to authenticate the SSL server and client. The SSL server and client obtain digital certificates through PKI. For more information about PKI and digital certificates, see "Configuring PKI."

• Integrity—SSL uses the message authentication code (MAC) to verify message integrity. It uses a MAC algorithm and a key to transform a message of any length to a fixed-length message. Any change to the original message will result in a change to the calculated fixed-length message. As shown in Figure 168, the message integrity verification process is as follows:

  1. The sender uses a MAC algorithm and a key to calculate a MAC value for a message. Then, it appends the MAC value to the message and sends the message to the receiver.

  2. The receiver uses the same key and MAC algorithm to calculate a MAC value for the received message, and compares it with the MAC value appended to the message.

  3. If the two MAC values match, the receiver considers the message intact. Otherwise, the receiver considers that the message was tampered with and it discards the message.