Mobile hotspots, i.e. Internet access services in moving networks (e.g. vehicular area networks (VAN) and personal area networks (PAN)) bring about new challenging issues. Even if the network mobility (NEMO) basic support protocol has been standardized as a mobility solution by the Internet Engineering Task Force (IETF), to the best of our knowledge, no studies have been conducted in the area of authentication, authorization, and accounting (AAA) protocol, which is a core technology for public mobile hotspots. In this paper, we propose a localized AAA protocol to retain the mobility transparency as the NEMO basic support protocol and to reduce the cost of the AAA procedure. In addition to providing mutual authentication, the proposed AAA protocol prevents various threats such as replay attack, man in the middle attack, and key exposure. Also, we develop an analytical model to evalutate the AAA signaling cost. Numerical results reveal that the proposed AAA protocol is a suitable solution for AAA services in different mobile hotspots.