Vehicular ad hoc network is a multihop mobile wireless communication network that can realize many vehicle-related applications through multitop communication. In the open wireless communication environment, security and privacy protection are important contents of VANET research. The most basic method of VANET privacy protection is anonymous authentication. Even through, there are many existing schemes to provide anonymous authentication for VANETs. Many existing schemes suffer from high computational cost by using bilinear pairing operation or need the assistance of the trust authorities (...) during the authentication process or rely on an ideal tamper-proof device, which requires very strong security assumption. In this study, an anonymous authentication and key negotiation scheme by using private key and group key is proposed, which is based on pseudonym using the nonsingular elliptic curve. In this scheme, there is no third party trust center to participate in the authentication, there is no need to query the database, and there is no need of the local database to save the identity information of many vehicles, which reduce the storage space and the authentication time compared with other schemes. The proposed scheme only needs realistic TPDs. In the proposed scheme, TPDs do not need to preinstall the system key as many other schemes do; hence, the failure of a single TPD does not affect the security of the entire system. The security of the scheme is proved under the random oracle model. Compared with the related schemes using bilinear pairings, the computational cost and communication cost of the proposed scheme are reduced by 82% and 50%, respectively. (shrink)

This paper aims to develop the description of move systems in Systemic Functional Linguistics based on dynamism in knowledge exchanges, that is, the possible move options made available at different points in an exchange concerned with the negotiation of information. Using conversational interactions in Khorchin Mongolian as examples, the paper argues that at different points in a knowledge exchange, both the speaker and the addressee’s knowledge of the information are at stake. The speaker may be positioned either as knowing or (...) as not knowing the information; at the same time the addressee may be positioned either as knowing or as not knowing the information. It is also possible for the interlocutors not to be positioned either way. The move systems developed make it possible to discuss the options preselected and activated at different points in a knowledge exchange and the way interlocutors are dynamically positioned as an exchange unfolds. (shrink)