Encryption and Authentication
EAX is a flexible nonce-using two-pass AEAD scheme with no restrictions on block cipher primitive to be used, nor on block size, and supports arbitrary-length messages. Authentication tag length is arbitrarily sizeable up to the used cipher's block size.
The block cipher primitive is used in CTR mode for encryption and as OMAC for authentication over each block through the EAX composition method, that may be seen as a particular case of a more general algorithm called EAX2 and described in "The EAX Mode of Operation" paper.
The reference implementation in the aforementioned paper uses AES in CTR mode for encryption combined with AES OMAC for authentication.
Read more about this topic: EAX Mode