CipherSuites and CipherSpecs

 

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Overview

A CipherSuite is a suite of cryptographic algorithms used by an SSL connection. A suite comprises three distinct algorithms:

• The key exchange and authentication algorithm, used during the SSL handshake
• The encryption algorithm, used to encipher the data
• The MAC (Message Authentication Code) algorithm, used to generate the message digest

There are several options for each component of the suite, but only certain combinations are valid when specified for an SSL connection. The name of a valid CipherSuite defines the combination of algorithms used. For example, the CipherSuite SSL_RSA_WITH_RC4_128_MD5 specifies:

• The RSA key exchange and authentication algorithm
• The RC4 encryption algorithm, using a 128-bit key
• The MD5 MAC algorithm

Several algorithms are available for key exchange and authentication, but the RSA algorithm is currently the most widely used. There is more variety in the encryption algorithms and MAC algorithms that are used.

A CipherSpec identifies the combination of the encryption algorithm and MAC algorithm. Both ends of an SSL connection must agree the same CipherSpec to be able to communicate.