920559
Verifiable distributed oblivious transfer and mobile agent security
The mobile agent is a fundamental building block of the mobile computing paradigm. In mobile agent security, oblivious transfer (OT) from a trusted party can be used to protect the agent's privacy and the hosts' privacy. In this paper, we introduce a new cryptographic primitive called Verifiable Distributed Oblivious Transfer (VDOT), which allows us to replace a single trusted party with a group of threshold trusted servers. The design of VDOT uses two novel techniques, consistency verification of encrypted secret shares and consistency verification through re-randomization. VDOT protects the privacy of both the sender and the receiver against malicious attacks of the servers. We also show the design of a system to apply VDOT to protect the privacy of mobile agents. Our design partitions an agent into the general portion and the security-sensitive portion. We also implement the key components of our system. As far as we know, this is the first effort to implement a system that protects the privacy of mobile agents. Our preliminary evaluation shows that protecting mobile agents not only is possible, but also can be implemented efficiently.
4409694
On route selection for interdomain traffic engineering
In this article we investigate a model of route selection for interdomain traffic engineering where routing to multiple destinations can be coordinated. We identify potential routing instability and inefficiency problems, and derive a set of practical guidelines to guarantee stability without global coordination. Using a realistic Internet topology, we show that route oscillations can happen even when a small number of ASes coordinate route selection for just a small number of destinations if the coordination does not follow our guidelines. Wc further extend our model so that ASes can adopt any route selection algorithms in a class of algorithms we call rational route selection algorithms; and the local ranking of routes of an AS can depend on ingress traffic patterns. We show that persistent route oscillations can happen in certain network settings even if the ASes strictly follow the constraints imposed by business considerations, and adopt any rational route selection algorithms.
2911118
A Theory of Network Localization
In this paper, we provide a theoretical foundation for the problem of network localization in which some nodes know their locations and other nodes determine their locations by measuring the distances to their neighbors. We construct grounded graphs to model network localization and apply graph rigidity theory to test the conditions for unique localizability and to construct uniquely localizable networks. We further study the computational complexity of network localization and investigate a subclass of grounded graphs where localization can be computed efficiently. We conclude with a discussion of localization in sensor networks where the sensors are placed randomly
2188314
Protocol design for scalable and reliable group rekeying
We present the design and specification of a protocol for scalable and reliable group rekeying together with performance evaluation results. The protocol is based upon the use of key trees for secure groups and periodic batch rekeying. At the beginning of each rekey interval, the key server sends a rekey message to all users consisting of encrypted new keys (encryptions, in short) carried in a sequence of packets. We present a scheme for identifying keys, encryptions, and users, and a key assignment algorithm that ensures that the encryptions needed by a user are in the same packet. Our protocol provides reliable delivery of new keys to all users eventually. It also attempts to deliver new keys to all users with a high probability by the end of the rekey interval. For each rekey message, the protocol runs in two steps: a multicast step followed by a unicast step. Proactive forward error correction (FEC) multicast is used to reduce delivery latency. Our experiments show that a small FEC block size can be used to reduce encoding time at the server without increasing server bandwidth overhead. Early transition to unicast, after at most two multicast rounds, further reduces the worst-case delivery latency as well as user bandwidth requirement. The key server adaptively adjusts the proactivity factor based upon past feedback information; our experiments show that the number of NACKs after a multicast round can be effectively controlled around a target number. Throughout the protocol design, we strive to minimize processing and bandwidth requirements for both the key server and users.
5645902
On designing incentive-compatible routing and forwarding protocols in wireless ad-hoc networks: an integrated approach using game theoretical and cryptographic techniques
In many applications, wireless ad-hoc networks are formed by devices belonging to independent users. Therefore, a challenging problem is how to provide incentives to stimulate cooperation. In this paper, we study ad-hoc games---the routing and packet forwarding games in wireless ad-hoc networks. Unlike previous work which focuses either on routing or on forwarding, this paper investigates both routing and forwarding. We first uncover an impossibility result---there does not exist a protocol such that following the protocol to always forward others' traffic is a dominant action. Then we define a novel solution concept called cooperation-optimal protocols. We present Corsac, a cooperation-optimal protocol consisting of a routing protocol and a forwarding protocol. The routing protocol of Corsac integrates VCG with a novel cryptographic technique to address the challenge in wireless ad-hoc networks that a link's cost (ie, its type) is determined by two nodes together. Corsac also applies efficient cryptographic techniques to design a forwarding protocol to enforce the routing decision, such that fulfilling the routing decision is the optimal action of each node in the sense that it brings the maximum utility to the node. Additionally, we extend our framework to a practical radio propagation model where a transmission is successful with a probability. We evaluate our protocols using simulations. Our evaluations demonstrate that our protocols provide incentives for nodes to forward packets.
3895085
Network localization in partially localizable networks
Knowing the positions of the nodes in a network is essential to many next generation pervasive and sensor network functionalities. Although many network localization systems have recently been proposed and evaluated, there has been no systematic study of partially localizable networks, i.e., networks in which there exist nodes whose positions cannot be uniquely determined. There is no existing study which correctly identifies precisely which nodes in a network are uniquely localizable and which are not. This absence of a sufficient uniqueness condition permits the computation of erroneous positions that may in turn lead applications to produce flawed results. In this paper, in addition to demonstrating the relevance of networks that may not be fully localizable, we design the first framework for two dimensional network localization with an efficient component to correctly determine which nodes are localizable and which are not. Implementing this system, we conduct comprehensive evaluations of network localizability, providing guidelines for both network design and deployment. Furthermore, we study an integration of traditional geographic routing with geographic routing over virtual coordinates in the partially localizable network setting. We show that this novel cross-layer integration yields good performance, and argue that such optimizations will be likely be necessary to ensure acceptable application performance in partially localizable networks.
5572574
Distributed Concurrency Control in Real-time Cooperative Editing Systems
Efficient distributed concurrency control is one of the most significant challenges in building real-time cooperative editing systems. In this paper, we focus on the definition and verification of an integrated set of distributed concurrency control schemes based on a novel consistency model for solving three inconsistency problems: divergence, causality-violation, and intention-violation in real-time cooperative editing systems.
753914
Integration of Semantic Tools into Document Editors
Integration of the tools used to prepare and verify software documents is vital to the eeectiveness of the software development process. This paper identiies the key requirements of such integration, outlines three possible paradigms for integration of semantic veriication tools with document editors, and reports on their prototype implementation and evaluation with respect to these requirements.
5382642
Multicode multirate compact assignment of OVSF codes for QoS differentiated terminals
Orthogonal variable spreading factor (OVSF) codes are used in both universal terrestrial radio access-frequency division duplex (UTRA-FDD) and time division duplex (UTRA-TDD) of the third-generation (3G) mobile communication systems. They can support multirate transmissions for mobile terminals with multicode transmission capabilities. In this paper, a new OVSF code assignment scheme, namely "multicode multirate compact assignment" (MMCA), is proposed and analyzed. The design of MMCA is based on the concept of "compact index" and takes into consideration mobile terminals with different multicode transmission capabilities and different quality of service (QoS) requirements. Priority differentiation between multirate realtime traffic and best-effort data traffic is also supported in MMCA. Analytical and simulation results show that MMCA is efficient and fair.
32772608
Issues on Supporting Distributed Software Processes
13986906
Decentralised Coordination for Software Process Enactment
Software process enactment mainly involves coordination of relevant team members to enact various tasks, which is supported by a centralised client/server architecture traditionally. This paper adopts concepts from peer-to-peer computing and presents an innovative approach to support decentralised process enactment. With this approach, team members are supported with coordination by direct communication among peers, which reflects applications’ increasingly distributed nature better. In addition, as a software process may be modelled incompletely at modelling time, a mechanism supporting run-time refinement of incomplete processes is also described in this paper.