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In this paper, we propose a navigation scheme that utilizes the online road information collected by a vehicular ad hoc network (VANET) to guide the drivers to desired destinations in a real-time and distributed manner. The proposed scheme has the advantage of using real-time road conditions to compute a better route and at the same time, the information source can be properly authenticated. To protect the privacy of the drivers, the query (destination) and the driver who issues the query are guaranteed to be unlinkable to any party including the trusted authority. We make use of the idea of anonymous credential to achieve this goal. In addition to authentication and privacy-preserving, our scheme fulfills all other necessary security requirements. Using the real maps of New York and California, we conducted a simulation study on our scheme showing that it is effective in terms of processing delay and providing routes of much shorter travelling time.

Vehicular ad hoc network (VANET) is an emerging type of networks which facilitates vehicles on roads to communicate for driving safety. The basic idea is to allow arbitrary vehicles to broadcast ad hoc messages (e.g. traffic accidents) to other vehicles. However, this raises the concern of security and privacy. Messages should be signed and verified before they are trusted while the real identity of vehicles should not be revealed, but traceable by authorized party. Existing solutions either rely heavily on a tamper-proof hardware device, or cannot satisfy the privacy requirement and do not have an effective message verification scheme. In this paper, we provide a software-based solution which makes use of only two shared secrets to satisfy the privacy requirement (with security analysis) and gives lower message overhead and at least 45% higher successful rate than previous solutions in the message verification phase using the bloom filter and the binary search techniques (through simulation study). We also provide the first group communication protocol to allow vehicles to authenticate and securely communicate with others in a group of known vehicles.

Abstract. Boyen [7] gave the first identity-based (ID-based) signcryption scheme that is forward secure, publicly verifiable as well as provably secure. However, his scheme aims at providing ciphertext unlinkability and anonymity which is not a desirable property in applications such as authentication of encrypted messages by firewalls [11], where any third party should be able to verify the origin of the ciphertext without knowing the content of the message and getting any help from the intended recipient. This requirement is referred as public ciphertext authenticity. In this paper, we give another ID-based signcryption scheme that can provide public ciphertext authenticity and is forward and provably secure as well as publicly verifiable. Our scheme is modified from Libert and Quisquater's ID-based signcryption scheme [16] and the efficiency of our scheme is comparable to other previous ID-based signcryption schemes.

Abstract. Identity-based (ID-based) cryptosystems eliminate the need for validity checking of the certificates and the need for registering for a certificate before getting the public key. These two features are desirable especially for the efficiency and the real spontaneity of ring signature, where a user can anonymously sign a message on behalf of a group of spontaneously conscripted users including the actual signer. In this paper, we propose a novel construction of ID-based ring signature which only needs two pairing computations for any group size. The proposed scheme is proven to be existential unforgeable against adaptive chosen message-and-identity attack under the random oracle model, using the forking lemma for generic ring signature schemes. We also consider its extension to support the general access structure.

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