52293772
Optimizing sensor movement planning for energy efficiency
Conserving the energy for motion is an important yet not-well-addressed problem in mobile sensor networks. In this paper, we study the problem of optimizing sensor movement for energy efficiency. We adopt a complete energy model to characterize the entire energy consumption in movement. Based on the model, we propose an optimal velocity schedule for minimizing energy consumption when the road condition is uniform; and a near optimal velocity schedule for the variable road condition by using continuous-state dynamic programming. Considering the variety in motion hardware, we also design one velocity schedule for simple microcontrollers, and one velocity schedule for relatively complex microcontrollers, respectively. Simulation results show that our velocity planning may have significant impact on energy conservation
62533537
Movement-Assisted Sensor Deployment
Abstract-Adequate coverage is very important for sensor networks to fulfill the issued sensing tasks. In many working environments, it is necessary to make use of mobile sensors, which can move to the correct places to provide the required coverage. In this paper, we study the problem of placing mobile sensors to get high coverage. Based on Voronoi diagrams, we design two sets of distributed protocols for controlling the movement of sensors, one favoring communication and one favoring movement. In each set of protocols, we use Voronoi diagrams to detect coverage holes and use one of three algorithms to calculate the target locations of sensors it holes exist. Simulation results show the effectiveness of our protocols and give insight on choosing protocols and calculation algorithms under different application requirements and working conditions.
7629821
Sensor relocation in mobile sensor networks
Recently there has been a great deal of research on using mobility in sensor networks to assist in the initial deployment of nodes. Mobile sensors are useful in this environment because they can move to locations that meet sensing coverage requirements. This paper explores the motion capability to relocate sensors to deal with sensor failure or respond to new events. We define the problem of sensor relocation and propose a two-phase sensor relocation solution: redundant sensors are first identified and then relocated to the target location. We propose a Grid-Quorum solution to quickly locate the closest redundant sensor with low message complexity, and propose to use cascaded movement to relocate the redundant sensor in a timely, efficient and balanced way. Simulation results verify that the proposed solution outperforms others in terms of relocation time, total energy consumption, and minimum remaining energy.
2378708
Cryptanalysis of Timestamp-Based Password Authentication Schemes Using Smart Cards
Password authentication is an important mechanism for remote login systems, where only authorized users can be authenticated via using their passwords and/or some similar secrets. In 1999, Yang and Shieh [14] proposed two password authentication schemes using smart cards. Their schemes are not only very efficient, but also allow users to change their passwords freely and the server has no need to maintain a verification table for authenticating users. However, their schemes are later identified to be flawed. To overcome those security flaws, Shen et al. [9] and Yoon et al. [17] proposed further improvements and claimed their new schemes are secure. In this paper, we first point out that Yang et al.'s attack [15] against Shen et al.'s scheme is actually invalid, since we can show that in a real implementation it is extremely difficult to find two hash values such that one is divisible by the other. After that, we show that both of Shen et al.' scheme and Yoon et al.'s scheme are insecure by identifying several effective impersonation attacks. Those attacks enable an outsider to be successfully authenticated and then enjoy the resources and/or services provided by the server.
10216231
On the Security of Two Threshold Signature Schemes with Traceable Signers
A (t,n) threshold signature scheme allows t or more group members to generate signatures on behalf of a group with n members, while any t-1 or less members cannot do the same thing. In 2001, based on a variant of ElGamal digital signature scheme, Li et al. proposed two (t,n) threshold signature schemes with traceable signers. One of their schemes needs the assistance of a mutually trusted center, while the other does not. In this paper, we present a security analysis on their schemes. We first point out that in fact signers in their schemes are untraceable, since anybody can convert a valid threshold signature into a new one such that another subset of group members will be wrongly considered as the signers of the new threshold signature for the same message. Furthermore, we demonstrate an attack to show that their second threshold signature scheme is insecure. In our attack, (n-t+1) colluding members can control the group secret key. Therefore, they can generate valid threshold signature for any message without the help of other members. Furthermore, honest members cannot detect this security flaw in the system, since any t members can generate threshold signatures according to the prescribed protocols.
17122000
Efficient and robust key management for large mobile ad hoc networks
Existing research efforts in key management can only handle very limited number of nodes and are vulnerable to active attacks. In addition, the flexibility and adaptivity of handling dynamic risks in different parts of networks, although critical in the practical usages of ad hoc networks, have been largely ignored. In this paper, we propose a novel hierarchical scheme based on threshold cryptography to address both security and efficiency issues of key management and certification service in Mobile Ad hoc Network (MANET). The main contributions of our key management scheme include: 1. providing various parts of MANET the flexibility of selecting appropriate security configurations, according to the risks faced; 2. providing the adaptivity to cope with rapidly-changing environments; 3. handling of MANETs with a large number of nodes; 4. issuing certificates with different levels of assurance. We also propose two algorithms, which can be used independently from the hierarchical structure, to protect certification services in ad hoc networks from active attacks. Our simulation results show that, compared to the previous work [16,18,19], our second algorithm is much faster in a friendly environment. When the key length is 1024 bits, the process of generating or renewing a certificate in our second algorithm is around six to eight times faster, and the process of generating partial certificates in our second algorithm is around 20-80 times faster. The latter advantage is critical in MANET where intrinsically the less help a node requests from its neighbors, the higher is the chance of obtaining the help. Furthermore, simulation results also show that our two algorithms work well in a hostile environment in which existing schemes work poorly.
1447896
Universal forgery on a group signature scheme using self-certified public keys
A group signature scheme allows any group member to sign messages on behalf of the group in an anonymous and unlinkable fashion. In the event of a dispute, a designated group manager can reveal the identity of the signer. In 1999, Tseng and Jan proposed a group signature scheme using self-certified public keys. By attacking their signature verification equation, we demonstrate that their scheme is universally forgeable, i.e., anybody can forge a valid group signature on any message such that the group manager is unable to determine the identity of the signer.
15430810
HARP: hard-wired routing pattern FPGAs
Modern FPGA architectures provide ample routing resources so that designs can be routed successfully. The routing architecture is designed to handle versatile connection configurations. However, providing such great flexibility comes at a high cost in terms of area, delay and power. We propose a new FPGA routing architecture\footnoteThis work was supported in part by a grant from NSF under contract CAREER CCF-0347891 that utilizes a mixture of hardwired and traditional flexible switches. The result is 24% reduction in leakage power consumption, 7% smaller area and 24% shorter delays, which translates to 30% increase in clock frequency. Despite the increase in clock speeds, the overall power consumption is %, including dynamic power, reduced by 8%.