17370273
On the Security of a Certified E-Mail Scheme with Temporal Authentication
Certified e-mail is a value-added service for standard e-mail systems, in which the intended recipient gets the mail content if and only if the mail originator receives a non-repudiation evidence that the message has been received by the recipient. As far as security is concerned, fairness is one of the most important requirements. Recently, Galdi and Giordano (2004) presented an optimistic protocol for certified e-mail with temporal authentication. In this paper, we analyze their protocol and demonstrate that it cannot achieve true fairness and has some other weaknesses. We further propose the improvements to avoid those security problems.
7098845
Security Analysis of Several Group Signature Schemes
At Eurocrypt’91, Chaum and van Heyst introduced the concept of group signature. In such a scheme, each group member is allowed to sign messages on behalf of a group anonymously. However, in case of later disputes, a designated group manager can open a group signature and identify the signer. In recent years, researchers have proposed a number of new group signature schemes and improvements with different levels of security. In this paper, we present a security analysis of several group signature schemes proposed in [25, 27, 18, 31]. By using the same method, we successfully identify several universally forging attacks on these schemes. In our attacks, anyone (not necessarily a group member) can forge valid group signatures on any messages such that the forged signatures cannot be opened by the group manager. We also discuss the linkability of these schemes, and further explain why and how we find the attacks.
16568303
Designated-verifier proxy signatures for e-commerce
In a designated-verifier proxy signature scheme, a user delegates her/his signing capability to another user in such a way that the latter can sign messages on behalf of the former, but the validity of generated signatures can only be checked by the designated verifier. In this paper, we first point out that one such scheme proposed recently by Dai et al. is insecure. To overcome the weaknesses in their scheme, based on the two-party Schnorr signature by Nicolosi et al., we present a new designated-verifier proxy signature scheme which is efficient and secure. Finally, we suggest the use of our scheme in electronic commerce applications, such as sale of digital products (digital music, movies, and books etc.).
17200585
Designated Verifier Signature Schemes: Attacks, New Security Notions and a New Construction
We show that the signer can abuse the disavowal protocol in the Jakobsson-Sako-Impagliazzo designated-verifier signature scheme. In addition, we identify a new security property—non-delegatability—that is essential for designated-verifier signatures, and show that several previously proposed designated-verifier schemes are delegatable. We give a rigorous formalisation of the security for designated-verifier signature schemes, and propose a new and efficient designated-verifier signature scheme that is provably unforgeable under a tight reduction to the Decisional Diffie-Hellman problem in the non-programmable random oracle model, and non-delegatable under a loose reduction in the programmable random oracle model. As a direct corollary, we also get a new efficient conventional signature scheme that is provably unforgeable under a tight reduction to the Decisional Diffie-Hellman problem in the non-programmable random oracle plus common reference string model.
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.
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.
1009884
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.
16185032
Using Social Contextual Information to Match Criminal Identities
Criminal identity matching is crucial to crime investigation in law enforcement agencies. Existing techniques match identities that refer to the same individuals based on simple identity features. These techniques are subject to several problems. First, there is an effectiveness trade-off between the false negative and false positive rates. The improvement of one rate usually lowers the other. Second, in some situations such as identity theft, simple-feature-based techniques are unable to match identities that have completely different identity feature values. We argue that the information about the social context of an individual may provide additional information for revealing the individual’s identity, helping improve the effectiveness of identity matching techniques. We define two types of social contextual features: role-based personal features and social group features. Experiments showed that social contextual features, especially the structural similarity and the relational similarity, significantly improved the precision without lowering the recall of criminal identity matching tasks.
12571017
A Metadata Integration Assistant Generator for Heterogeneous Distributed Databases
This paper describes a metadata interchange approach for semi-automatedin tegration of heterogeneous distributedd atabases. Our system prototype uses distributed metadata to generate a GUI tool for a meta-user (who does the metadata integration) to describe mappings between master and source databases by assigning index number and specifying conversion function names; the system uses Quilt as its XML query language. The queries for the local databases being transparent for users are generated, which is based on the metadata built semi-automatically. An experiment testing feasibility is reportedin which 3 different publishers' databases are integrated.
8431943
GPU-friendly warped display for scope-maintained video surveillance
In this paper, we propose an efficient technique for warped display of surveillance video signal. Usually, there are regions of interest (ROIs) in video surveillance, such as entrance or exit, and moving objects or persons. The surveillant has two or more conflicting goals in mind. He/She wants to blow up the ROIs, but also wants to have an overview of the whole surveillance scope. The proposed method solves this conflict by warping the input video signal in real time fashion. First, multiple ROIs are detected. Then, the mesh for texture mapping is deformed, according to the position and shape of the ROIs. The original video frame is mapped as a texture on the deformed mesh to produce the warped effect. Mesh deformation and texture mapping are accelerated by modern graphics processing units (GPU). By allocating more display space for ROIs, the proposed technique highlights such important regions and assists the surveillant to locate them effectively. By experiments, we show that the proposed method is effective and efficient.
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