Revocation Messages Research Articles

VANET Security through Group Broadcast Encryption

VANET security is an evolving topic in mobile networks, as providing a secure layer of communications in such a dynamic and fast network is a challenge. The work presented in this article was conducted in order to verify and evaluate the feasibility of applying group broadcast cryptography to the VANET environment, as an attempt to gain performance by decreasing the number of messages in the wireless network. Group broadcast is a symmetric/asymmetric hybrid cryptography method, aiming to merge the best of the two approaches without their major drawbacks. Simulations were set-up and run using the ONE simulator, comparing the usage of the three different cryptography approaches for VANETs. Results consider the number of connections, the number messages and the number of revocation messages per day. The resulting data promises that group broadcast encryption can be used to simplify the encrypting phase, reduce required storage and significantly decrease the number of messages in the network.

Traceable Identity-Based Group Signature

Group signature is a useful cryptographic primitive, which makes every group member sign messages on behalf of a group they belong to. Namely group signature allows that group member anonymously signs any message without revealing his/her specific identity. However, group signature may make the signers abuse their signing rights if there are no measures of keeping them from abusing signing rights in the group signature schemes. So, group manager must be able to trace (or reveal) the identity of the signer by the signature when the result of the signature needs to be arbitrated, and some revoked group members must fully lose their capability of signing a message on behalf of the group they belong to. A practical model meeting the requirement is verifier-local revocation, which supports the revocation of group member. In this model, the verifiers receive the group member revocation messages from the trusted authority when the relevant signatures need to be verified. With the rapid development of identity-based cryptography, several identity-based group signature (IBGS) schemes have been proposed. Compared with group signature based on public key cryptography, IBGS can simplify key management and be used for more applications. Although some identity-based group signature schemes have been proposed, few identity-based group signature schemes are constructed in the standard model and focus on the traceability of signature. In this paper, we present a fully traceable (and verifier-local revocation) identity-based group signature (TIBGS) scheme, which has a security reduction to the computational Diffie-Hellman (CDH) assumption. Also, we give a formal security model for traceable identity-based group signature and prove that the proposed scheme has the properties of traceability and anonymity.

Improved VLR Group Signature Based on DTDH Assumption

In VLR (verifier-local revocation) group signatures, revocation messages are only sent to signature verifiers (as opposed to both signers and verifiers). Consequently there is no need to contact individual signers when some user is revoked. Since signers have no load, the VLR group signature schemes are suitable for mobile environments. To meet the requirement of speediness in mobile communication, reducing computation costs and shortening signature length are two requirements at the current research of VLR group signatures. Based on this idea, an improved version of Zhou’s VLR group signature is given. Compared with the original scheme, the improved scheme not only can achieve the same security level, but also has shorter signature size and lower computation costs.

ServBGP: BGP-inspired autonomic service routing for multi-provider collaborative architectures in the cloud

In this paper we propose the design and implementation of ServBGP, a service routing protocol for managing service collaboration among cloud providers in cloud computing. ServBGP is based on the policy-driven design of the well-known BGP Internet routing protocol to support the different service interaction models currently employed in the cloud particularly the monolithic, composite, and broker-based service models. The main contribution of this work lies in devising a system that autonomously manages the different aspects of service interaction and collaboration among service providers from service discovery and advertisement to service consumption and revocation. The ServBGP routing decision engine is designed to operate by (1) processing cost-bidding service advertisement and revocation messages from the different cloud providers and (2) extracting objective and trustworthy feedback which is maintained by certified network entities and which consists of a set of reputation scores related to quality of service, security, and pricing. The BGP-inspired design choice allows the proposed system to “stand upon the shoulders of giants” by relying on a time-tested protocol that currently supports scalable inter-domain routing services among over 120,000 IPv4 prefixes in the Internet. Moreover, reusing the decision logic of the standard BGP protocol aids in reducing the development and operational costs, hence shortening the time to market, and utilizing a large set of BGP extensions, particularly, in the security domain, that have been incorporated into BGP since its inception in 1989. These qualities are of a chief importance in the cloud community today to ensure the efficient and secure service collaboration among cloud providers and to support the evolution, scalability, and economic feasibility of the overall cloud computing infrastructure. A proof of concept implementation of the ServBGP design is realized on the NetKit network emulation and virtualization platform using the standard BGPv4 protocol. Moreover, the devised ServBGP design is developed from the ground up and deployed in a real cloud computing environment using Amazon EC2, Microsoft Azure, and Google App Engine cloud platforms.

Improved efficiency for revocation schemes via Newton interpolation

We present a novel way to implement the secret-sharing-based family of revocation schemes of Naor and Pinkas [2003]. The basic scheme of [Naor and Pinkas 2000] uses Shamir's polynomial secret-sharing to revoke up to r users, where r is the degree of the secret-sharing polynomial, and it is information theoretically secure against coalitions of up to r collaborators. The nonrevoked users use Lagrange interpolation in order to compute the new key. Our basic scheme uses a novel modification of Shamir's polynomial secret-sharing: The secret equals the leading coefficient of the polynomial (as opposed to the free coefficient as in the original scheme) and the polynomial is reconstructed by Newton interpolation (rather than Lagrange interpolation). Comparing our scheme to one variant of the Naor--Pinkas scheme, we offer revocation messages that are shorter by a factor of almost 2, while the computation cost at the user end is smaller by a constant factor of approximately 13/2. Comparing to a second variant of the Naor--Pinkas scheme, our scheme offers a reduction of O ( r ) in the computation cost at the user end, without affecting any of the other performance parameters. We then extend our basic scheme to perform multiround revocation for stateless and stateful receivers, along the lines offered by Naor and Pinkas [2000] and Kogan et al. [2003]. We show that using Newton rather than Lagrange interpolants enables a significantly more efficient transmission of the new revocation message and shorter response time for each round. Pay TV systems that implement broadcast encryption techniques can benefit significantly from the improved efficiency offered by our revocation schemes.

A Public-Key Traitor Tracing Scheme with Revocation Using Dynamic Shares

We proposed a new public-key traitor tracing scheme with revocation capability using dynamic shares and entity revocation techniques. Our scheme’s traitor tracing and revocation programs cohere tightly. The size of the enabling block of our scheme is independent of the number of receivers. Each receiver holds one decryption key only. The distinct feature of our scheme is that when traitors are found, we can revoke their private keys (up to some threshold z) without updating the private keys of other receivers. In particular, no revocation messages are broadcast and all receivers do nothing. Previously proposed revocation schemes need update existing keys and entail large amount of broadcast messages. Our traitor tracing algorithm works in a black-box way. It is conceptually simple and fully k-resilient, that is, it can find all traitors if the number of them is k or less. The encryption algorithm of our scheme is semantically secure assuming that the decisional Diffie-Hellman problem is hard.