An authentication apparatus, included in a device supporting a network communication, includes a certificate handler that receives a certificate of an opponent and parses or verifies the certificate of the opponent. Cryptographic primitives receive an authentication request of the opponent, generate a random number in response to the authentication request, generate a challenge corresponding to the random number, and verify a response of the opponent corresponding to the challenge. A shared memory stores the parsed certificate, the random number, the challenge, and the response. An authentication controller controls the certificate handler, the cryptographic primitives, and the shared memory through a register setting, according to an authentication protocol.