Intermediate Pseudonym Certificate Generation for C-ITS

One of the most known mechanism to ensure privacy is the use of anonymity which means that drivers have to change their identity as much as possible. In the meantime, each message has to be authenticated when it is sent. To do so, each driver should sign its messages using its private key and has to send its certificate along with the message. The use of one certificate per driver will not ensure privacy since a certificate is easily correlated to the driver identity. For this reason, each driver will use a set of certificates denoted pseudonyms certificates (PC) Each vehicle has a set of PCs which will be used to sign sent messages and will be used as a part of the driver id. A PC is used for a limited period of time. In this paper we allow to a vehicle to generate additional PCs to its neighbors when they are close together for a period of time. It will allow to these neighbors to have more PCs. The neighbors will be able to change their PCs more frequently. Our choice is to allow a pseudonym derivation when a minimum number of vehicles are driving close to each other. The disadvantage of such a method is the network overhead which will increase due to sending of the driver vehicle certificate in each sent message.