|
Counter Mode Cipher Block Chaining Message Authentication Code Protocol, Counter Mode CBC-MAC Protocol or simply CCMP (CCM mode Protocol) is an encryption protocol designed for Wireless LAN products that implement the standards of the IEEE 802.11i amendment to the original IEEE 802.11 standard. CCMP is an enhanced data cryptographic encapsulation mechanism designed for data confidentiality and based upon the Counter Mode with CBC-MAC (CCM) of the AES standard. It was created to address the vulnerabilities presented by WEP, a dated, insecure protocol.〔 ==Technical details== CCMP uses CCM that combines CTR for data confidentiality and CBC-MAC for authentication and integrity. CCM protects the integrity of both the MPDU data field and selected portions of the IEEE 802.11 MPDU header. CCMP is based on AES processing and uses a 128-bit key and a 128-bit block size. CCMP uses CCM with the following two parameters: * M = 8; indicating that the MIC is 8 octets (eight bytes). * L = 2; indicating that the Length field is 2 octets. A CCMP Medium Access Control Protocol Data Unit (MPDU) comprises five sections. The first is the MAC header which contains the destination and source address of the data packet. The second is the CCMP header which is composed of 8 octets and consists of the packet number (PN), the Ext IV, and the key ID. The packet number is a 48-bit number stored across 6 octets. The PN codes are the first two and last four octets of the CCMP header and are incremented for each subsequent packet. Between the PN codes are a reserved octet and a Key ID octet. The Key ID octet contains the Ext IV (bit 5), Key ID (bits 6-7), and a reserved subfields (bits 0-4). CCMP uses these values to encrypt the data unit and the MIC. The third section is the data unit which is the data being sent in the packet. Lastly are the Message Integrity Code (MIC) which protects the integrity and authenticity of the packet and the frame check sequence (FCS) which is used for error detection and correction. Of these sections only the data unit and MIC are encrypted.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「CCMP」の詳細全文を読む スポンサード リンク
|