Efficient and fair radio resource allocation is essential for wireless networking systems. Most existing fairness-aware dynamic spectrum allocation-based schemes target at instantaneous or short-term resource allocation optimization. However, due to the dynamic nature of wireless networks (in terms of network topologies, traffic demands, qualify-of-service (QoS) requirements, etc.), the resource allocation problem cannot be optimized by only considering instantaneous or short-term resource allocation. In fact, with the fast growing applications of elastic traffic (e.g., video streaming, video conferencing), it is highly desirable to achieve efficient and fair radio resource allocation over a long period of time. In this paper, we propose a long-term fairness-aware dynamic resource allocation mechanism to achieve better system performance (in terms of total network data rate and user fairness). To model the optimal long-term fairness-aware dynamic resource allocation, the stochastic game is adopted to analyze the effect of historical resource allocation on the future network performance. In this scheme, the efficient and fair radio resource allocation for each time slot is optimized with the consideration of the long-term utility. The simulation results show significant performance enhancement in terms of both fairness index and throughput of our mechanism compared to classic dynamic spectrum allocation schemes.

Database-as-a-Service is becoming more and more popular for many organizations. Storing data on the cloud can significantly reduce costs in terms of maintenance costs and initial investment costs. But due to data privacy and security concerns, many companies are still reluctant to use outsourced database service. In this paper, we present a solution to protect data privacy on the cloud, at the same time, allowing multiple users accessing the shared database with security assurance.

The research on reliable communication in distributed networks has a rich history due to its fundamental importance. In this paper, an efficient implementation of reliable broadcast communications in the stand-alone and simulation- based framework is formalized and analyzed by means of sequential aggregate signatures. A reliable broadcast problem is called stand-alone if the security of broadcast protocols can be efficiently reduced to the security of the underlying digital signatures. A reliable broadcast is called secure in the simulation- based framework if it is provably secure in the universally composable paradigm. Our reliable broadcast protocol works in the unknown fixed-identity networks where no public key infrastructure (PKI) exists. We show that our implementation is robust in the sense that the proposed broadcast protocol can resist against up to k adversaries assuming that the underlying network is (2k + l)-vertex connected and individual signatures are secure against adaptive chosen-message attack.

Databases associated with keywords, can be public, private or hybrid, as a result the solutions to keyword search protocols for each type are different. In this paper, we study the problem of privacy-preserving keyword search in the public database model where the data-item is public but a client wishes to retrieve some data-item or search data-item, without revealing to the server which item it is. The contribution of this paper is of three fold. In the first fold, an efficient implementation of oblivious linear function evaluation protocols for secure two-party computation of a linear function over a finite field that does not emulate the circuit for computing oblivious linear function while at the same time it is provably secure against malicious adversary is presented. We show our implementation is provably secure assuming that the underlying Fujisaki-Okamoto's commitment scheme is informational hiding and computational binding as well Paillier's encryption scheme is semantically secure in the common reference string model. In the second fold, we further extend the techniques to non-linear polynomials and thus provide a secure reduction of OPE protocols of a polynomial of degree m, to m OPEs of linear polynomials. In the third fold, we use the OPEs for solving the oblivious keyword search problem along the Ogata and Kurosawa's ad hoc methodology, and show that our implementation is provably secure assuming that the underlying Fujisaki-Okamoto's commitment scheme is informational hiding and computational binding, Paillier's encryption scheme is semantically secure, G is a pseudo-random function in the common reference string model.

An important issue in mobile commerce (m-commerce) is to exchange digital data between two distributed parties in an efficient and fair manner. In this paper, a lightweight stand-alone and setup-free verifiably committed signature based on Schnorr signature scheme which aims to achieve efficiency and fairness for m-commerce is proposed. The idea behind of our construction is to encrypt the salt of a partial signature rather than to encrypt the whole partial signature. As a result, our construction is more efficient and thus more suitable for mobile environment compared with the best results in the literature. We further show that our scheme is provably secure in the random oracle model assuming that the Schnorr's signature scheme is secure against adaptive chosen message attack and Paillier's encryption scheme is one-way.

As content delivery to wireless devices becomes faster and scalable, it is likely that mobile commerce will constitute a significant portion of digital commerce. In markets, business activities are coordinated through prices- values businesses assigns to resources. Since different businesses usually assign different values to the same resource, the parties involved need to negotiate a mutually acceptable agreement, the agreement details both sensitive and valuable and should be well protected. Although numerous implementations of fair-exchange protocols have been proposed, research addressing secure yet efficient price negotiation systems has not been reported. In this paper, we propose a novel price negotiation protocol. We make three contributions to price negotiation protocols for M-commerce. Firstly, we propose a new notion called revealable ring-signatures and formalize it. Using revealable ring-signatures, we derive our price negotiation protocols. Secondly,we provide an efficient implementation of revealable ring-signatures by allowing an individual party to generate a committed string so that a real signer can be traced when the committed string is revealed. Finally, we show that our implementation is provably secure in the random oracle model assuming that discrete logarithm over Z*pis hard.

In this paper, a novel information theoretical model for trust metrics in complex environments is proposed and analyzed. The contribution of this paper is two folds. In the first fold, syntax of actions is introduced and formalized in the context of disjunctive normal form over multiple Boolean variables, and random variables for describing an agent's behavior is formalized based on the notion of actions and auxiliary information (and auxiliary functions). The notion of trust is then formalized as a combination of a predicator and an evaluator of the current auxiliary information. In the second fold, we model contribution of a recommender's by a well studied notion - mutual information of variables of behavior and variables of auxiliary information. We show that our trust metrics is sound in the sense that - the definition of trust metrics is transitive; if a node (form the point view of the subject) in a recommendation path is not trusted by the subject, the contribution of this recommendation path is zero; the longer the size of a recommendation path, the less trust value should be computed from individual recommenders along the path. The proposed trust evaluation system is useful in reputation systems, risk management, collaborative filtering and social networking services.

This paper studies practical auction systems for allocating resources in the wireless environments. The contribution of this paper is two-fold. In the first fold, a novel solution to mobile auction (m-auction) systems is presented based on the notion of convertibly undeniable signatures which in turn, can be viewed as a light-weight version of verifiably encrypted signatures in the bulletin board model. The idea behind of our construction is simple yet useful - we view salts that are used to mask convertibly undeniable signatures as public keys for authenticating bidding flows in m-auction systems. As a result, the cost of communication and computation for refreshing auxiliary information is zero and thus our systems are suitable for mobile devices whose computation resources are limited. In the second fold, we show that our implementation enjoys the following nice features: (i) it is provably secure in the standard intractability paradigm;(ii) it is provably secure against signature forgery attack; (iii) it is indistinguishable (addressing the stand-alone property of convertible signatures).

Ad-hoc networks formed by peers without relying on any preexisting infrastructure, have been a very attractive field of academic and industrial research in recent years due to their potential applications. An ad-hoc network allows a peer node further to form a task-driven sub-network such that each node in the generated sub-network may exchange data with each other but any other non-member node is prohibited to access the subnetwork. As a result, a task-driven subnetwork generated by a peer node definitely requires membership proof mechanism (in the scenario of anonymous communications, anonymous membership proof systems are required). In this paper, we provide a novel mechanism for anonymous access control (anonymous membership proof systems) in ad- hoc networks based on a new notion which we call or-protocols in the common reference string model. An or-protocol in essence is a three move zero-knowledge proof system that allows a peer node to prove its membership of a given set which is publicly verifiable. Our protocol is of constant size, i.e., the length of a proof is independent with number of users in a given set, and thus is suitable for practice. Furthermore we show that our protocol is provably secure assuming that the discrete logarithm problem defined over prime field is hard.

Although radio frequency identification (RFID) technology is promising, it is vulnerable and subject to a wide range of attacks due to possible tags compromise, difficulty in physical protection, absence of infrastructure and so on. Generally speaking, the threat to RFID systems mainly comes from the illegal reader's attempt to compromise tag identity. In order to protect the tag carries' privacy (intuitively, privacy for RFID tags means that the communication of a tag does not allow an adversary to determine the identity of the tag (non-traceability), however the reader should be able to determine whether the tag it reads is valid (completeness) and only such tags (soundness)), a security model that supports the analytical argument of properties, addressing both security and performance issues for RFID tags is introduced and formalized in this paper. The significant feature of our model is that a back-end database for a reader is explicitly introduced which allows the reader to search key-index set used by individual tags more efficiently, and describe the protocols in a unique way, where properties can be isolated and analyzed. We then propose an authentication protocol for securing RFID tags, and show that our implementation is completeness, soundness and non-traceability in the independent random oracle model.

The performance of ad-hoc networks depends on trust among distributed nodes. To enhance security in ad-hoc networks, it is important to evaluate trustworthiness of other nodes without centralized authorities. This paper studies trust metrics of recommendation systems in ad-hoc networks and makes the following three contributions: 1. the notion of action is formalized by means of disjunctive normal form (DNF) over Boolean variables and then the notion of trust is formalized in terms of action via transitive disclosure graphs; 2. a new trust metrics is formalized by means of mutual information, and we show that our trust metrics enjoys the following nice features: if a subject does not trust an intermediate node in a path, then trust value of the recommendation along the path is not trusted at all; the longer of a recommendation path, the less trust value along the path; and the trust reserves the transitivity; 3. our trust metrics satisfies Yao's Minmax principle. As a result, the expected running time of the optimal deterministic algorithm for an arbitrary chosen input distribution of auxiliary information is a lower bound on the expected running time of the optimal randomized algorithm for trust metrics. To the best of our knowledge, the ideas using mutual information to quantify trust and using maxmin to calculate trust established through multiple recommendation paths are first proposed in this paper. Since the claimed properties of our metrics cover all axioms of (Sun et al., 2006) and (Sun et al., 2006), it follows that our trust metrics can be viewed as a dynamic metrics of Sun et al's measurement while the later should be viewed as a static trust metrics where no recommendation is allowed. Finally, the efficiency of our maxmin mechanism for computing of trust may render it to be a highly reliable tool for stimulating cooperative behavior in ad-hoc networks.

It is an open problem of how to protect the traffics and at the same time, to support In-network processing in sensor networks. This paper tackles the problem by proposing an efficient model of categorizing encrypted data transmitted on sensor networks. An aggregator, an intermediate sensor node in our setting, is embedded with a set of searching in encrypted format. Upon receiving an encrypted message it matches the message with the keywords and then processes the message based on certain policies such as forwarding the original message to the next hop updating it and forwarding or simply dropping it on detecting duplicates. The messages are encrypted before being sent out and decrypted only at their destination. Although the intermediate classifiers can categorize the messages they learn nothing about the encrypted messages except several encrypted keywords even the statistic information. The secure and efficient aggregation SEA scheme uses Bloom filter to further reduce transmission cost. The performance analysis shows that the computational cost and communication cost are well balanced.

In this paper, we first propose almost optimal sequential aggregate signatures in the simulation-based paradigm. We then provide an immediate application of the new primitive to construct compact routing discovery protocols

In this paper, a novel system level methodology for evaluating functionalities of network systems within general security model is introduced and formalized. We first decompose the entire system into a collection of subsystems each associated with a functionality. Thereafter, a new model for evaluating security properties of individual subsystem is built, which intends to implement a functionality by allowing an adversary to learn information and obtain knowledge from the correspondent subsystem via oracle queries. We further define evaluation and security metrics for security qualifications which is shown to be complete and robust within our model

In traditional public key infrastructures, centralized certification authorities are indispensable for managing public key certificates that are used to provide the witness of certain NP relations. However, it is difficult to deploy centralized certification authorities in ad hoc networks due to the lack of infrastructure and other central services. Nevertheless, public key management protocols-the fundamental security issues, should be proposed to nodes in a self-organized ad hoc network so that each node within this group can collaborate to others to compute certain tasks if its certificate is valid. In this paper, a secure yet efficient group signature scheme is first constructed which is provably secure within our model assuming that the strong RSA problem defined over Z/sub n/*, together with the decisional Diffie-Hellman defined over the quadruple residue QR/sub N//spl epsi/Z/sub N/* is hard. We then propose a public key management protocol for self-organized ad hoc networks by simply assuming that a group manager issues certificates to the nodes who want to join in and at the same time it revokes the certificates related those who are leaving. The technique presented in this paper is universal, and it can be used to numerous applications, e.g., the construction of anonymous routing protocols and incentive-based services in social networks, and so on.

Anonymous routing protocols must be equipped with secure anonymous identification protocols for ad-hoc access, otherwise, successive nodes cannot he convinced that the request messages are from a specified set in which each node will provide service for path discovery requests. In this paper, we study anonymous identification schemes in the setting where each participant generates its public key and maintains the correspondent secret key independently. The presented scheme is efficient as we separate soundness and honest verifier zero-knowledge from the hardness of any problem. The security of our construction can be rigorously proved by simply assuming that each challenge string is chosen uniformly at random by the honest verifier. Finally, we provide alternative construction by reducing the 3-move protocol to 2-move protocol assuming that the RSA problem is hard.

Personal electronic devices, with short-range wireless capability are becoming commonplace. Wireless enabled devices belonging to the same user (domain) need to be associated long-term to each other with as much ease as connections with physical wires. It should be obvious which two devices are being associated. Managing device associations must be simple, intuitive and communication between associated devices secure. This paper describes touch-mediated association protocols (TAP) which enable user-friendly, secure long-term device associations. TAP extends the resurrecting duckling security model. It uses an intuitive UI (the mediator), a physical device which taps devices that need to be associated. TAP does not require any PKI, uses computationally cheap cryptography and is easy to integrate.

Sequential aggregate signature, first introduced and formalized by A. Lysyanskaya et al. (see EUROCRYPT 2004, p.74-90, 2004), is emerging as a useful tool to ensure routing security and at the same time to improve performance. We propose a new mechanism to construct sequential aggregate signatures based on the cipher block chaining (CBC) mode, which is different from previous known results. We then construct an efficient sequential aggregate signature scheme and show that our construction is provably secure in the random oracle paradigm, assuming that the RSA problem is hard. Finally, we propose an interesting aggregate routing protocol for wireless ad hoc networks as an immediate application of our protocol.