A method and authentication apparatus for sharing information for identifying an Authorization Key (AK) with a Base Station (BS) in a subscriber station are provided. The method includes, in the subscriber station, sharing a root key with the BS by performing an authentication with the BS, sharing an AK derived from the root key with the BS, sharing an AK sequence number of the AK with the BS, and sharing an AK Identifier (AKID) of the AK with the BS. The AK sequence number is generated by a sequence number of the root key. The AKID is generated by a parameter including the AK, the AK sequence number, a Medium Access Control (MAC) address of the subscriber station, and a BS Identifier (BSID) of the BS.