Method and apparatus of cipher communication for management frame using quality of service mechanism in wireless local area network system

An apparatus for performing cipher communication in a wireless local area network system, the apparatus comprising:

• a radio frequency unit configured to transmit and/or receive a radio signal;
• and
• a processor coupled to the radio frequency unit and configured to:
• obtain a pseudo noise (PN) code sequence for a plaintext Medium Access Control. (MAC) protocol data unit (MPDU);
• construct an additional authentication data (AAD) by using at least one field in a header of the plaintext MPDU;
• construct a Nonce from the PN code sequence, an Address 2 field in the header of the plaintext MPDU and a Priority Field in the header of the plaintext MPDU;
• generate a counter mode (CTR) with cipher block, chaining (CBC)-MAC Protocol (CCMP) header including a new PN code sequence and a key identifier;
• generate encrypted data and Message Integrity Code (MIC) by using a temporal key, the AAD, and the Nonce;
• and
• generate an encrypted MPDU to be transmitted to a peer station by combining the header of the plaintext MPDU, the CCMP header, the encrypted data and the MIC,
• wherein, if the plaintext MPDU is a management frame and Quality of service Management Frame (QMF) is supported, a priority subfield included in the Nonce is set to a value in an access category field of a sequence number field included in the management frame, and
• wherein, if the plaintext MPDU is the management frame and management frame protection is negotiated, a management subfield included in the Nonce is set to a predefined value.