A cipher is the algorithm used to encrypt and decrypt data in the encryption process. Some ciphers are stronger than others, meaning that a message encrypted by a stronger cipher is more difficult for an unauthorized person to decrypt.
A cipher operates on data by applying a key to the data. Generally, the longer the key the cipher users during encryption, the more difficult it is to decrypt the data without the proper decryption key.
When a client initiates an SSL connection with Messaging Server, the client lets the server know what ciphers and key lengths it prefers to use for encryption. In any encrypted communication, both parties must use the same ciphers. Because there are a number of cipher-and-key combinations in common use, a server should be flexible in its support for encryption. For more information on ciphers, see Chapter 23, Configuring Security and Access Control, in Sun Java System Messaging Server 6.3 Administration Guide.