Renwei Ge

Approximate message authentication and biometric entity authentication

Approximate Message Authentication Code (AMAC) is a recently introduced cryptographic primitive with several applications in the areas of cryptography and coding theory. Briefly speaking, AMACs represent a way to provide data authentication that is tolerant to acceptable modifications of the original message. Although constructs had been proposed for this primitive, no security analysis or even modeling had been done. In this paper we propose a rigorous model for the design and security analysis of AMACs. We then present two AMAC constructions with desirable efficiency and security properties. AMAC is a useful primitive with several applications of different nature. A major one, that we study in this paper, is that of entity authentication via biometric techniques or passwords over noisy channels. We present a formal model for the design and analysis of biometric entity authentication schemes and show simple and natural constructions of such schemes starting from any AMAC.

Improved topology assumptions for threshold cryptography in mobile ad hoc networks

Mobile Ad Hoc Networks (MANET), due to their lack of physical infrastructures or centralized authorities, pose a number of security challenges to a protocol designer. In particular, several typical application scenarios demand the design of protocols that cannot base their security on the existence of trusted parties or setup information, but rather need to leverage uniquely on assumptions limiting the corrupting power of the adversaries. This naturally defines security design and analysis paradigms similar to those of the Threshold Cryptography area, where it is typically assumed that an adversary can corrupt up to a limited amount of entities or resources. Therefore a secure realization of primitives from Threshold Cryptography in MANET promises to be applicable to several MANET protocols.Recently, in [10], we started the analysis of Threshold Cryptography solutions over MANET, by focusing on the problem of extending to these networks known efficient threshold signature schemes for wired networks. In particular, we noted a major design difficulty due to the lack of full network connectivity that significantly constrained the network topology assumptions under which a MANET threshold signature scheme can be proved secure. In this paper we continue our investigation and present a new MANET threshold signature scheme that is secure under significantly improved topology assumptions. Surprisingly, we break through an apparent barrier due to well-known results from the Distributed Computing area.

Securing reliable server pooling in MANET against byzantine adversaries

Reliable server pooling (rSerPool) is an architecture and a set of protocols allowing a service provider to run several servers that can reliably provide the same service. Should a particular server fail while providing its service, another server can efficiently replace it. This property is attractive not only for wired but also for wireless networks. However, the unique characteristics of mobile ad hoc networks (MANETs) bring serious reliability and security challenges to the application of rSerPool. In this paper, we perform a comprehensive investigation of the security of rSerPool in MANET against both server failures and, especially, Byzantine attacks. We formulate security requirements for rSerPool in MANET and design efficient, distributed, and survivable security solutions for both main phases of rSerPool: service discovery and service provision. Specifically, we secure the service discovery phase by using a secure multiple-dominating set creation protocol, and the service provision phase by using a novel type of threshold signature scheme. Both protocols address novel security goals and are of independent interest as they can find applications to other areas; most notably, the construction of a distributed and survivable public-key infrastructure in MANET.

Threshold cryptography in mobile ad hoc networks

The area of Threshold Cryptography investigates the design and analysis of protocols that distribute, in wired networks, cryptographic actions usually performed by a single party into multi-party variants, where the original action is successfully performed only if at least a certain threshold of the participants are available and not corrupted. As of today, several examples of threshold cryptographic protocols (e.g., signatures, public-key cryptosystems, zero-knowledge protocols, etc.) are being investigated in the Cryptography literature. We note that the impact of the Threshold Cryptography paradigm is of even greater importance to study the security of other types of communication networks, such as Mobile Ad Hoc Networks, where the existence and availability of trusted authorities is severely limited by intrinsic network features, and problems such as avoiding a “single point of failure”, or, more generally, “service availability”, become crucial. In this paper we formalize, investigate and present satisfactory solutions for the general problem of Threshold Cryptography in Mobile Ad Hoc Networks. Although we restrict our study to the cryptographic operation of digital signatures schemes, our definitional approaches can be extended to most other cryptographic actions studied in Threshold Cryptography.

Efficient and secure indirect-address service discovery in MANET

Service discovery protocols address the problem of preliminary association or storage of services at specific service providers and, at a later stage, efficient lookup for providers responsible for demanded clients services, in mobile ad hoc networks (MANET) used for military applications, both the efficiency of service discovery- protocols and the security of such protocols against adversaries are of crucial importance for the success of, say, battlefield operations. In this paper we consider a recently proposed lookup protocol that satisfies interesting efficiency properties by using an approach reminiscent of indirect-address storage techniques, and thus significantly different from other well-known flooding-type approaches. We observe that this protocol can be adapted to obtain a service discovery protocol in MANET. Specifically, we build an index system that matches services to their correspondent service agents; then servers register themselves to selected agents, and clients can efficiently retrieve the service information from the specific service agents. We then investigate the problem of securing the proposed protocol against Byzantine adversaries. Our main result is the design and analysis of a both efficient and secure service discovery protocol based on indirect-address techniques

Design and analysis of DBMAC, an error localizing message authentication code

The paper introduces a new construct of message authentication codes called DBMAC. It can not only provide the message authentication functionality but also localize a few errors in the message. DBMAC uses a conventional MAC in its construction such that it inherits the conventional MACs resistance to forgeries. Furthermore, the division and butterfly structure gives the capability of localizing a few errors. Our construction can be proved to have almost optimal asymptotic tag length. We also extensively analyze the error correction capabilities of our construction for small message length values.

Threshold cryptography in mobile ad hoc networks under minimal topology and setup assumptions

Abstract Mobile Ad Hoc Networks (MANET), due to their lack of physical infrastructures or centralized online authorities, pose a number of security challenges to a protocol designer. In particular, several typical application scenarios demand the design of protocols that cannot base their security on the existence of trusted parties or setup information, but rather need to leverage uniquely on assumptions limiting the corrupting power of the adversaries. This naturally defines security design and analysis paradigms similar to those of the threshold cryptography area, where it is typically assumed that an adversary can corrupt up to a limited amount of entities or resources. Therefore a secure realization of primitives from threshold cryptography in MANET promises to be applicable to several MANET protocols. However, directly applying known threshold cryptography solutions for wired network into MANETs faces serious challenges. In particular, we noted a major design difficulty due to the lack of full network connectivity that significantly constrained the network topology assumptions under which a MANET threshold signature scheme can be proved secure. In this paper we formalize, investigate and present a new MANET threshold signature scheme that is secure under significantly improved topology and setup assumptions. Surprisingly, we break through an apparent barrier due to well-known results from the distributed computing area.

Securing weakly-dominating virtual backbones in mobile ad hoc networks

Virtual backbone structures are of fundamental importance in mobile ad hoc networks (MANET) as they are essential to support various applications such as service discovery and provision, multicast, routing, etc. In this paper we consider a very natural approach for the creation of virtual backbones, based on weakly-dominating sets, and investigate its security properties against Byzantine adversaries that can corrupt up to a given threshold of nodes. We formalize the notion of secure protocols for the creation and management of virtual backbones, and design a distributed protocol generating weakly-dominating virtual backbones, that is both efficient, according to standard MANET metrics, and secure against Byzantine adversaries corrupting up to a given threshold of nodes