6256815
Cryptanalysis of the Public-Key Encryption Based on Braid Groups
At CRYPTO 2000, a new public-key encryption based on braid groups was introduced. This paper demonstrates how to solve its underlying problem using the Burau representation. By this method, we show that the private-key can be recovered from the public-key for several parameters with significant probability in a reasonable time. Our attack can be mounted directly on the revised scheme mentioned at ASIACRYPT 2001 as well. On the other hand, we give a new requirement for secure parameters against our attack, which more or less conflicts with that against brute force attack.
26868655
Complexity of the generalized conjugacy problem
Recently, the generalized conjugacy problem(GCP) in braid groups was introduced as a candidate for cryptographic one-way function. A GCP in a braid group can be transformed into a GCP in a general linear group by the Burau representation. We study the latter problem induced in this way.
8508201
Cryptanalysis of Some Group-Oriented Proxy Signature Schemes
A proxy signature scheme allows an entity to delegate its signing power to another entity. Since the notion of proxy signatures was first introduced, many proxy signature schemes and various extensions have been considered. As an example, the notion of threshold proxy signature or proxy multi-signature was introduced as a group-oriented variant. In this paper, we show that the threshold proxy signature scheme proposed by Hsu and Wu, and the proxy multi-signature schemes independently proposed by Chen et al. and Hsu et al. are all insecure against the malicious original singer(s). Our result provides a simple example that the way to put the secret parts together should be carefully considered.
26579916
A Monge Property for the D-dimensional Transportation Problem
Abstract In 1963, Hoffman gave necessary and sufficient conditions under which a family of O( mn )-time greedy algorithms solves the classical two-dimensional transportation problem with m sources and n sinks. One member of this family, an algorithm based on the “northwest corner rule”, is of particular interest, as its running time is easily reduced to O(m + n). When restricted to this algorithm, Hoffman's result can be expressed as follows: the northwest-corner-rule greedy algorithm solves the two-dimensional transportation problem for all source and supply vectors if and only if the problem's cost array C = { c [ i , j ]} possesses what is known as the (two-dimensional) Monge property, which requires c [ i 1 , j 1 ] + c [ i 2 , j 2 ] ⩽ c [ i 1 , j 2 ] + c [ i 2 , j 1 ] for i 1 i 2 and j 1 j 2 . This paper generalizes this last result to a higher dimensional variant of the transportation problem. We show that the natural extension of the northwest-corner-rule greedy algorithm solves an instance of the d -dimensional transportation problem if and only if the problem's cost array possesses a d -dimensional Monge property recently proposed by Aggarwal and Park in the context of their study of monotone arrays. We also give several new examples of cost arrays with this d -dimensional Monge property.
13229931
A Haptic Teleoperation Approach Based on Contact Force Control
This paper presents a new teleoperation approach using a virtual spring, and local contact force control on the slave robot. The operational space framework provides the control structure needed to achieve decoupled task dynamics. A virtual spring connects the master and slave systems and a closed-loop force controller compensates for the dynamics of the slave system, rendering transparent the effector of the slave robotic system. The active force control approach allows the desired motion and contact forces to be combined in a single force command. The required performance and robustness of force control are achieved by a full state reconstruction using a modified Kalman estimator, which addresses disturbances and modeling uncertainties. The performance of both telepresence and force control are further improved by on-line stiffness estimation of the object in contact with the effector. The redundancy of the mobile manipulation system is addressed through a decoupled decomposition of task and posture dynamics.
45151226
A Framework for Trusted Wireless Sensor Networks
Wireless sensor technologies have become increasingly important in a variety of areas, including mission-critical applications. However, there are still many obstacles that we need to overcome before we apply the current wireless sensor network (WSN) technologies. Unlike traditional computing devices in a wired environment, the WSN faces significant challenges from wireless node devices, which usually have limitations in computational power, energy, and their working environment. In this paper we introduce a framework for a trusted large-scale WSN that provides a longer sensor lifetime, cost effectiveness, security, survivability, and scalable management. Our framework uses clustering mechanisms and multiple cluster heads within a cluster where we switch the cluster heads based on their current energy levels or security/survivability reasons. We also present the Extended Random Key Pre-distribution scheme adapted for such a framework.
45167088
Moving Object Inference Engine and Applying to Battlefield
15933972
A logical specification for usage control
Recently presented usage control (UCON) has been considered as the next generation access control model with distinguishing properties of decision continuity and attribute mutability. Ausage control decision is determined by combining authorizations, obligations, and conditions, presented as UCONABC core models by Park and Sandhu. Based on these core aspects, we develop afirst-order logic specification of UCON with Lamport's temporallogic of actions (TLA). The building blocks of this model include:(1) a sequence of states expressed by attributes of subjects, objects, and the system, (2) state predicates on subject andobject attributes, (3) pre-defined authorization actions performed by the security system and subjects, (4) obligation actions, and(5) condition predicates on system attributes. For a UCON model we define a set of temporal logic formulas that hold as usage control policies. We show the flexibility and expressive capability of this logic model by specifying the new features and core models of UCON.