Vehicular Ad hoc Networks (VANETs) are so difficult to secure due to the wireless technology and its several known security holes. To protect against attacks, methods and techniques have been developed. The Intrusion Detection System (IDS) can detect malicious actions made to the system. In vehicular ad hoc networks, IDSs are in charge of analyzing incoming and outgoing packets to identify malicious signatures. However, without a decision making mechanism, they are useless. This paper designs a decision making protocol for security information in VANETs. Our study is based on two IDS approaches. In the first one, the IDS are installed on vehicles, while in the second one they are installed on the Road Side Units (RSU). In both approaches, vehicles are grouped according to their speed. Corroboration of an attack is based on a probabilistic model of ratio computation between vehicles or RSUs having answered to the signature of the attack. Our aim is to design a decision support mechanism. The dynamic topology of VANET allows a strong prevention by broadcasting the information. So when an attack occurs, the protocol allows the corroboration of the latter and alert neighboring clusters.

We propose in this paper a security protocol based on periodic change of pseudonyms. The idea is to avoid illegal traceability of vehicles during their communications and preserve their privacy and confidential information. Two different approaches are proposed. In the first approach, each vehicle asks the central authority a new communication pseudonym after a time t. While in the second approach, each vehicle generates itself after a time t, a new communication pseudonym. Our objective is to permit at least two vehicles to change their pseudonym in the same time interval. We evaluate in this work, the bandwidth used by considering the vehicles speed in each approach. The proposed protocol is based on equidistant distribution of the road side unit and uses the average of speed permitted on the road to evaluate lifetime t of the communication's pseudonyms and certificates. The exchange of information is based on asymmetric and symmetric cryptography scheme and it uses hash function. Our protocol provides authentication, non-repudiation and privacy.

The combination of text classification and maximal association rules will allow the extraction of hidden knowledge, often relevant from the text and allow the detection of dependencies and correlations between the relevant units of information (words) of different classes. In fact, the results of text classification take the form of large and noisy classes of similarities.