Privacy is guaranteed through encryption. Although information can still be intercepted by a third party they will be unable to read them as they have no access to the encryption key. Integrity is also ensured through encryption. If information is received that will not decrypt properly then the recipient knows that the information has been tampered with during transmission.
Authentication is provided through digital certificates.
Digital certificates provide the basis for secure electronic transactions as they enable all participants in a transaction to quickly and easily verify the identity of the other participants. Initially, the client and server exchange public keys, and then the client generates a private encryption key that is used only for this transaction. This is referred to as a session key. The client then encrypts the session key with the server's public key and sends it to the server. Then, for the rest of the transaction, the client and the server can use the session key for private-key encryption.