WAPI (WLAN Authentication and Privacy Infrastructure) is a Chinese national standard for securing wireless networks. It consists of two main parts: WLAN Authentication Infrastructure (WAI) for identity authentication and WLAN Privacy Infrastructure (WPI) for data protection. The WPI protocol is responsible for data encryption and integrity. It explicitly mandates the use of the SM4 block cipher (formerly known as SMS4), a 128-bit block cipher that is also a Chinese national standard, for ensuring data confidentiality over the wireless link.

A. Web (WEP): WEP (Wired Equivalent Privacy) is an obsolete and insecure IEEE 802.11 security protocol, entirely separate from the WAPI standard.

C. TKIP: The Temporal Key Integrity Protocol (TKIP) is the encryption method used in the WPA (Wi-Fi Protected Access) standard, not in WAPI.

D. CCMP: The Counter Mode Cipher Block Chaining Message Authentication Code Protocol (CCMP) is the mandatory encryption standard for WPA2 and is also used in WPA3, not WAPI.

1. Huawei Enterprise Support Documentation, WLAN Security Feature Guide. In sections detailing the configuration of WAPI security policies, the documentation specifies that the WPI protocol uses the SM4 algorithm for data encryption. (e.g., in documentation for Huawei ACs and APs under WLAN Service Configuration > Security Profile Configuration).

2. Chinese National Standard GB 15629.11-2003, "Information technology... Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications," Amendment XG1-2006. This standard, which defines WAPI, specifies the SMS4 (later renamed SM4) algorithm for the WPI component.

3. Zhang, Y., & Zheng, J. (2005). Security of the WAPI protocol. In Cryptology and Network Security, 4th International Conference, CANS 2005, Xiamen, China, December 14-16, 2005, Proceedings (Vol. 3810, p. 158). Springer. The paper states, "The encryption algorithm used in WPI is a block cipher with 128-bit key and 128-bit block size, called SMS4." (Section 2.2 WPI). DOI: https://doi.org/10.1007/1159937112