Method for allocating authorization key identifier for wireless portable internet system

An authentication apparatus of a subscriber station, the apparatus comprising:

• at least one processor configured to perform an authentication with a base station, and to obtain a context associated with the authentication,
• wherein the context comprises:
• an AK derived from a root key that is generated by performing the authentication with the base station;
• an AK sequence number of the AK, the AK sequence number being generated by a sequence number of the root key;
• and
• an AK identifier (AKID) of the AK, the AKID being generated by a parameter comprising the AK, the AK sequence number, a medium access control (MAC) address of the subscriber station, and a base station identifier (BSID) of the base station.

An authentication apparatus of a base station, the apparatus comprising:

• at least one processor configured to perform an authentication with a subscriber station, and to obtain a context associated with the authentication,
• wherein the context comprises:
• an AK derived from a root key that is generated by performing the authentication with the subscriber station;
• an AK sequence number of the AK, the AK sequence number being generated by a sequence number of the root key;
• and
• an AK identifier (AKID) of the AK, the AKID being generated by a parameter comprising the AK, the AK sequence number, a medium access control (MAC) address of the subscriber station, and a base station identifier (BSID) of the base station.