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The amazing proliferation of communication technologies for embedded systems opens the way for completely new applications but forces designers to adopt new methodologies to meet time-to-market constraints. Computer-Aided Design (CAD) has been traditionally applied to computers and embedded systems in isolation without considering them as a global inter-connected system. The paper contributes to fill this gap by proposing 1) a communication-aware design flow for network-interconnected embedded systems and 2) a formal framework to efficiently synthesize their network aspects by formulating and solving an optimization problem. Presented case studies show the potentiality of the proposed approach to address heterogeneous scenarios, e.g., related to smart spaces up to the ever-more-mentioned Internet-of-Things. [ABSTRACT FROM AUTHOR]

We provide a framework to analyze multi-level checkpointing protocols, by formally defining a k -level checkpointing pattern. We provide a first-order approximation to the optimal checkpointing period, and show that the corresponding overhead is in the order of \sum _{\ell =1}^{k}\sqrt{2\lambda _\ell C_\ell} , where \lambda _\ell$ is the error rate at level  $\ell$ , and $C_\ell$ the checkpointing cost at level $\ell$ . This nicely extends the classical Young/Daly formula on single-level checkpointing. Furthermore, we are able to fully characterize the shape of the optimal pattern (number and positions of checkpoints), and we provide a dynamic programming algorithm to determine the optimal subset of levels to be used. Finally, we perform simulations to check the accuracy of the theoretical study and to confirm the optimality of the subset of levels returned by the dynamic programming algorithm. The results nicely corroborate the theoretical study, and demonstrate the usefulness of multi-level checkpointing with the optimal subset of levels. [ABSTRACT FROM AUTHOR]

We focus on protocols for auditable restoration of distributed systems. The need for such protocols arises due to conflicting requirements (e.g., access to the system should be restricted but emergency access should be provided). One can design such systems with a tamper detection approach (based on the intuition of In-case-of-emergency-break-glass). However, in a distributed system, such tampering, which are denoted as auditable events, is visible only for a single node. This is unacceptable since the actions they take in these situations can be different than those in the normal mode. Moreover, eventually, the auditable event needs to be cleared so that system resumes the normal operation. With this motivation, in this paper, we present two protocols for auditable restoration, where any process can potentially identify an auditable event. The first protocol has an unbounded state space while the second protocol uses bounded state space that does not increase with the length of the computation. In both protocols, whenever a new auditable event occurs, the system must reach an auditable state where every process is aware of the auditable event. Only after the system reaches an auditable state, it can begin the operation of restoration. Although any process can observe an auditable event, we require that only authorized processes can begin the task of restoration. Moreover, these processes can begin the restoration only when the system is in an auditable state. Our protocols are self-stabilizing and can effectively handle the case where faults or auditable events occur during the restoration protocol. Moreover, they can be used to provide auditable restoration to other distributed protocols. [ABSTRACT FROM PUBLISHER]

Cache coherence plays a major role in manycore systems. The verification of deadlocks is a challenge in particular, because deadlock freedom is an emerging property. Formal methods often decouple verification of the protocol from verification of the communication interconnect. Modern communication fabrics, however, become more advanced and include a network topology, routing, arbitration, synchronization, and more. In this paper, an integrated approach is proposed that allows cross-layer verification of both the cache coherence protocol and the communication fabric all at once. An automated methodology for deriving cross-layer invariants is proposed. These invariants relate the state of the application-layer protocols to en route packets in the communication fabric. Using the invariants, we derive formal proofs of deadlock-freedom for two case studies: a directory-based MI protocol in a 2D mesh, and a ring-based snoopy protocol in a 2D torus. Additionally, we show that our methodology can be used to derive the smallest possible queue sizes that ensure absence of deadlocks. Our methodology is generally applicable and shows promising scalability. [ABSTRACT FROM PUBLISHER]

In a two-server password-authenticated key exchange (PAKE) protocol, a client splits its password and stores two shares of its password in the two servers, respectively, and the two servers then cooperate to authenticate the client without knowing the password of the client. In case one server is compromised by an adversary, the password of the client is required to remain secure. In this paper, we present two compilers that transform any two-party PAKE protocol to a two-server PAKE protocol on the basis of the identity-based cryptography, called ID2S PAKE protocol. By the compilers, we can construct ID2S PAKE protocols which achieve implicit authentication. As long as the underlying two-party PAKE protocol and identity-based encryption or signature scheme have provable security without random oracles, the ID2S PAKE protocols constructed by the compilers can be proven to be secure without random oracles. Compared with the Katz et al.'s two-server PAKE protocol with provable security without random oracles, our ID2S PAKE protocol can save from 22 to 66 percent of computation in each server. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a framework for privacy-preserving outsourced functional computation across large-scale multiple encrypted domains, which we refer to as POFD. With POFD, a user can obtain the output of a function computed over encrypted data from multiple domains while protecting the privacy of the function itself, its input and its output. Specifically, we introduce two notions of POFD, the basic POFD and its enhanced version, in order to tradeoff the levels of privacy protection and performance. We present three protocols, named Multi-domain Secure Multiplication protocol (MSM), Secure Exponent Calculation protocol with private Base (SECB), and Secure Exponent Calculation protocol ( SEC), as the core sub-protocols for POFD to securely compute the outsourced function. Detailed security analysis shows that the proposed POFD achieves the goal of calculating a user-defined function across different encrypted domains without privacy leakage to unauthorized parties. Our performance evaluations using simulations demonstrate the utility and the efficiency of POFD. [ABSTRACT FROM AUTHOR]

Decentralized attribute-based encryption (ABE) is a variant of multi-authority based ABE whereby any attribute authority (AA) can independently join and leave the system without collaborating with the existing AAs. In this paper, we propose a user collusion avoidance scheme which preserves the user's privacy when they interact with multiple authorities to obtain decryption credentials. The proposed scheme mitigates the well-known user collusion security vulnerability found in previous schemes. We show that our scheme relies on the standard complexity assumption (decisional bilienar Deffie-Hellman assumption). This is contrast to previous schemes which relies on non-standard assumption (q-decisional Diffie-Hellman inversion). [ABSTRACT FROM PUBLISHER]

One of the main reasons why Byzantine fault-tolerant (BFT) systems are currently not widely used lies in their high resource consumption: 3f+1 replicas are required to tolerate only f faults. Recent works have been able to reduce the minimum number of replicas to 2f+1 by relying on trusted subsystems that prevent a faulty replica from making conflicting statements to other replicas without being detected. Nevertheless, having been designed with the focus on fault handling, during normal-case operation these systems still use more resources than actually necessary to make progress in the absence of faults. This paper presents Resource-efficient Byzantine Fault Tolerance (ReBFT), an approach that minimizes the resource usage of a BFT system during normal-case operation by keeping f replicas in a passive mode. In contrast to active replicas, passive replicas neither participate in the agreement protocol nor execute client requests; instead, they are brought up to speed by verified state updates provided by active replicas. In case of suspected or detected faults, passive replicas are activated in a consistent manner. To underline the flexibility of our approach, we apply ReBFT to two existing BFT systems: PBFT and MinBFT. [ABSTRACT FROM PUBLISHER]

Covert channels are widely considered as a major risk of information leakage in various operating systems, such as desktop, cloud, and mobile systems. The existing works of modeling covert channels have mainly focused on using finite state machines (FSMs) and their transforms to describe the process of covert channel transmission. However, a FSM is rather an abstract model, where information about the shared resource, synchronization, and encoding/decoding cannot be presented in the model, making it difficult for researchers to realize and analyze the covert channels. In this paper, we use the high-level Petri Nets (HLPN) to model the structural and behavioral properties of covert channels. We use the HLPN to model the classic covert channel protocol. Moreover, the results from the analysis of the HLPN model are used to highlight the major shortcomings and interferences in the protocol. Furthermore, we propose two new covert channel models, namely: (a) two channel transmission protocol (TCTP) model and (b) self-adaptive protocol (SAP) model. The TCTP model circumvents the mutual inferences in encoding and synchronization operations; whereas the SAP model uses sleeping time and redundancy check to ensure correct transmission in an environment with strong noise. To demonstrate the correctness and usability of our proposed models in heterogeneous environments, we implement the TCTP and SAP in three different systems: (a) Linux, (b) Xen, and (c) Fiasco.OC. Our implementation also indicates the practicability of the models in heterogeneous, scalable and flexible environments. [ABSTRACT FROM AUTHOR]

This paper reveals an intrinsic relationship between secure cloud storage and secure network coding for the first time. Secure cloud storage was proposed only recently while secure network coding has been studied for more than ten years. Although the two areas are quite different in their nature and are studied independently, we show how to construct a secure cloud storage protocol given any secure network coding protocol. This gives rise to a systematic way to construct secure cloud storage protocols. Our construction is secure under a definition which captures the real world usage of the cloud storage. Furthermore, we propose two specific secure cloud storage protocols based on two recent secure network coding protocols. In particular, we obtain the first publicly verifiable secure cloud storage protocol in the standard model. We also enhance the proposed generic construction to support user anonymity and third-party public auditing, which both have received considerable attention recently. Finally, we prototype the newly proposed protocol and evaluate its performance. Experimental results validate the effectiveness of the protocol. [ABSTRACT FROM PUBLISHER]

Distributed Transactional Memory (DTM) is a recent but promising model for programming distributed systems. It aims to present programmers with a simple to use distributed concurrency control abstraction (transactions), while maintaining performance and scalability similar to distributed fine-grained locks. Any complications usually associated with such locks (e.g., distributed deadlocks) are avoided. In this article, we analyze the use of open nesting in the DTM setting. We extend two DTM algorithms, Transactional Forwarding Algorithm (TFA) and SCORe with support for open nested transactions and we implement them into two frameworks for running distributed transactions, such as Hyflow and Infinispan. We discuss the mechanisms and performance implications of such nesting, and identify the cases where using open nesting is warranted and the relevant parameters for such a decision. To the best of our knowledge, our work also contributes the first ever implementations of DTM systems with support for open-nested transactions. [ABSTRACT FROM PUBLISHER]

With the rapid proliferation of RFID technologies, RFID has been introduced into applications such as inventory and sampling inspection. Conventionally, in RFID systems, the reader usually identifies all the RFID tags in the interrogation region with the maximum power. However, some applications may only need to identify the tags in a specified area, which is usually smaller than the reader’s default interrogation region. An example could be identifying the tags in a box, while ignoring the tags out of the box. In this paper, we respectively present two solutions to identify the tags in the specified area. The principle of the solutions can be compared to the picture-taking process of an auto-focus camera, which firstly focuses on the target automatically and then takes the picture. Similarly, our solutions first focus on the specified area and then shoot the tags. The design of the two solutions is based on the extensive empirical study on RFID tags. Realistic experiment results show that our solutions can reduce the execution time by $44$ percent compared to the baseline solution, which identifies the tags with maximum power. Furthermore, we improve the proposed solutions to make them work well in more complex environments. [ABSTRACT FROM AUTHOR]

With the ongoing shift of network services to the application layer also the monitoring systems focus more on the data from the application layer. The increasing speed of the network links, together with the increased complexity of application protocol processing, require a new way of hardware acceleration. We propose a new concept of hardware acceleration for flexible flow-based application level traffic monitoring which we call Software Defined Monitoring. Application layer processing is performed by monitoring tasks implemented in the software in conjunction with a configurable hardware accelerator. The accelerator is a high-speed application-specific processor tailored to stateful flow processing. The software monitoring tasks control the level of detail retained by the hardware for each flow in such a way that the usable information is always retained, while the remaining data is processed by simpler methods. Flexibility of the concept is provided by a plugin-based design of both hardware and software, which ensures adaptability in the evolving world of network monitoring. Our high-speed implementation using FPGA acceleration board in a commodity server is able to perform a 100 Gb/s flow traffic measurement augmented by a selected application-level protocol analysis. [ABSTRACT FROM AUTHOR]

Broadcast encryption (BE) schemes allow a sender to securely broadcast to any subset of members but require a trusted party to distribute decryption keys. Group key agreement (GKA) protocols enable a group of members to negotiate a common encryption key via open networks so that only the group members can decrypt the ciphertexts encrypted under the shared encryption key, but a sender cannot exclude any particular member from decrypting the ciphertexts. In this paper, we bridge these two notions with a hybrid primitive referred to as contributory broadcast encryption (ConBE). In this new primitive, a group of members negotiate a common public encryption key while each member holds a decryption key. A sender seeing the public group encryption key can limit the decryption to a subset of members of his choice. Following this model, we propose a ConBE scheme with short ciphertexts. The scheme is proven to be fully collusion-resistant under the decision $n$ -Bilinear Diffie-Hellman Exponentiation (BDHE) assumption in the standard model. Of independent interest, we present a new BE scheme that is aggregatable. The aggregatability property is shown to be useful to construct advanced protocols. [ABSTRACT FROM AUTHOR]

Embedded transaction design inside solid state drives (SSDs) is an attractive way to support system consistency with low overhead due to the no-overwrite property of flash memory. Recent research proposes shadow paging variants to reduce write traffic to SSDs for longer lifetime while leveraging the random performance of SSDs. However, writes in transactions usually are small, and the page-aligned shadow paging protocols still incur high write amplification, which hurts SSD lifetime. In this paper, we propose an embedded transaction protocol, DiffTx, which differentially logs partial page updates in a write-ahead logging way and writes full page updates in a shadow paging way, aiming at low write amplification. DiffTx further improves transaction performance using two techniques. First, by clustering mapping metadata of full page updates with differential data of partial page updates in a single record, DiffTx tracks pages of each transaction at low overhead. Second, DiffTx removes the write ordering on commit by delaying the completeness check of writes, leveraging the clean-state write property of flash memory. Experiments show that DiffTx improves throughput by 25.9 percent and halves write traffic on average compared to TxFlash, a typical embedded transaction protocol for flash memory. [ABSTRACT FROM AUTHOR]

Recently, a number of extended Proxy Re-Encryptions (PRE), e.g. Conditional (CPRE), identity-based PRE (IPRE) and broadcast PRE (BPRE), have been proposed for flexible applications. By incorporating CPRE, IPRE and BPRE, this paper proposes a versatile primitive referred to as conditional identity-based broadcast PRE (CIBPRE) and formalizes its semantic security. CIBPRE allows a sender to encrypt a message to multiple receivers by specifying these receivers’ identities, and the sender can delegate a re-encryption key to a proxy so that he can convert the initial ciphertext into a new one to a new set of intended receivers. Moreover, the re-encryption key can be associated with a condition such that only the matching ciphertexts can be re-encrypted, which allows the original sender to enforce access control over his remote ciphertexts in a fine-grained manner. We propose an efficient CIBPRE scheme with provable security. In the instantiated scheme, the initial ciphertext, the re-encrypted ciphertext and the re-encryption key are all in constant size, and the parameters to generate a re-encryption key are independent of the original receivers of any initial ciphertext. Finally, we show an application of our CIBPRE to secure cloud email system advantageous over existing secure email systems based on Pretty Good Privacy protocol or identity-based encryption. [ABSTRACT FROM AUTHOR]

Duty cycling mode is widely adopted in wireless sensor networks to save energy. Existing duty-cycling protocols cannot well adapt to different data rates and dynamics, resulting in a high energy consumption in real networks. Improving those protocols may require global information or heavy computation and thus may not be practical, leading to many empirical parameters in real protocols. To fill the gap between the application requirement and protocol performance, in this paper, we analyze the energy consumption for duty cycled sensor networks with different data rates. Our analysis shows that existing protocols cannot lead to an efficient energy consumption in various scenarios. Based on the analysis, we design a light-weight adaptive duty-cycling protocol (LAD), which reduces the energy consumption under different data rates and protocol dynamics. LAD can adaptively adjust the protocol parameters according to network conditions such as data rate and achieve an optimal energy efficiency. To make LAD practical in real network, we further pre-calculate optimal parameters offline and store them on sensor nodes, which significantly reduces the computation time. We theoretically validate the performance improvement of the protocol. We implement the protocol in TinyOS and extensively evaluate it on 40 TelosB nodes. The evaluation results show the energy consumption can be reduced by 28.2-40.1 percent compared with state-of-the-art protocols. Results based on data from a 1,200-node operational network further show the effectiveness and scalability of the design. [ABSTRACT FROM AUTHOR]

Recently, the IEEE 802.15.6 Task Group introduced a new wireless communication standard that provides a suitable framework specifically to support the requirements of wireless body area networks (WBANs). The standardization dictates the physical (PHY) layer and medium access control (MAC) layer protocols for WBAN-based communications. Unlike the pre-existing wireless communication standards, IEEE 802.15.6 standardization supports short-range, extremely low power wireless communication with high quality of service and support for high data rates upto 10 Mbps in the vicinity of living tissues. In this work, we construct a discrete-time Markov chain (DTMC) that efficiently depicts the states of an IEEE 802.15.6 CSMA/CA-based WBAN. Following this, we put forward a thorough analysis of the standard in terms of reliability, throughput, average delay, and power consumption. The work concerns non-ideal channel characteristics and a saturated network traffic regime. The major shortcoming of the existing literature on Markov chain-based analysis of IEEE 802.15.6 is that the authors did not take into consideration the time spent by a node awaiting the acknowledgement frame after transmission of a packet, until time-out occurs. Also, most of the work assume that ideal channel characteristics persist for the network which is hardly the case in practice. This work remains distinctive as we take into account the waiting time of a node after it transmits a packet while constructing the DTMC. Based on the DTMC, we perform a user priority (UP)-wise analysis, and justify the importance of the standard from a medical perspective. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel zero knowledge grouping proof protocol for RFID Systems. Over the years, several protocols have been proposed in this area but they are either found to be vulnerable to certain attacks or do not comply with the EPC Class $1$ Gen $2$ (C1G2) standard because they use hash functions or other complex encryption schemes. Also, the unique design requirements of grouping proofs have not been fully addressed by many. Our protocol addresses these important security and design gaps in grouping proofs. We present a novel approach based on pseudo random squares and quadratic residuosity to realize a zero knowledge system. Tag operations are limited to functions such as modulo (MOD), exclusive-or (XOR) and $128$  bit Pseudo Random Number Generators (PRNG). These can be easily implemented on passive tags and hence achieves compliance with the EPC Global standard while meeting the security requirements. [ABSTRACT FROM AUTHOR]

A new methodology for DRAM performance analysis has been proposed based on accurate characterization of DRAM bus cycles. The proposed methodology allows cycle-accurate performance analysis of arbitrary DRAM traces, obviates the need for functional simulations, allows accurate estimation of DRAM performance maximum, and enables root causing of suboptimal DRAM operation. [ABSTRACT FROM AUTHOR]

Several papers have studied fault attacks on computing a pairing value $e(P,Q)$ , where $P$ is a public point and $Q$ is a secret point. In this paper, we observe that these attacks are in fact effective only on a small number of pairing-based protocols, and that too only when the protocols are implemented with specific symmetric pairings. We demonstrate the effectiveness of the fault attacks on a public-key encryption scheme, an identity-based encryption scheme, and an oblivious transfer protocol when implemented with a symmetric pairing derived from a supersingular elliptic curve with embedding degree 2. [ABSTRACT FROM PUBLISHER]

In modern System on Chip (SoC) designs, the multi-cycle delays on long interconnects between synchronously clocked IP blocks are accommodated by latency insensitive protocols (LIP) through extra valid/stall handshakes between components and additional logic blocks called relay stations. The use of handshaking interconnects and relay stations leads to area and latency penalties, that must be minimized for cost effective SoC designs. Interconnected IP blocks with certain graph topology have periodic behaviors that can be exploited to remove the need for handshake interconnects. Unfortunately, the periodic schedule may not exist for any LIS designs consist of two or more strongly connected components. Some of these systems are not bounded without back pressure. In the past, back pressure between SCCs has always been implemented as stall signals in the backward direction, and they are required to prevent overflow. In this paper, we propose an LIS design optimization algorithm which computes a minimum set of back pressure arcs required between SCCs. We model an LIS by a partial back pressure graph (PBPG) and show that the boundedness of a PBPG can be verified by checking the reachability in its strongly connected component graph (SCCG). Based on this, we formulate the problem of finding a minimum set of back pressure arcs (MBPA) and show that this problem can be reduced to the Minimum Cost Arborescence (MCA) problem for directed graphs. This allows us to obtain a polynomial time algorithm for synthesizing a minimum cost LIS implementation starting from a synchronous model of the original system. After adding back pressure arcs, we develop a localized Mixed Integer Linear Programming (LMILP) approach to optimize the throughput of the resulting LIS. This approach scales better than existing MILP-based throughput optimization techniques. In addition, we also provide an implementation of the LIS which refines its PBPG model. To the best of our knowledge, this is the first effort that considers the optimization of back pressure and throughput together in the design of latency insensitive systems. [ABSTRACT FROM AUTHOR]

Cache coherence protocols limit the scalability of multicore and manycore architectures and are responsible for an important amount of the power consumed in the chip. A good way to alleviate these problems is to introduce a local memory alongside the cache hierarchy, forming a hybrid memory system. Local memories are more power-efficient than caches and do not generate coherence traffic, but they suffer from poor programmability. When non-predictable memory access patterns are found, compilers do not succeed in generating code because of the incoherence between the two storages. This paper proposes a coherence protocol for hybrid memory systems that allows the compiler to generate code even in the presence of memory aliasing problems. Coherence is ensured by a software/hardware co-design where the compiler identifies potentially incoherent memory accesses and the hardware diverts them to the correct copy of the data. The coherence protocol introduces overheads of 0.26% in execution time and of 2.03% in energy consumption to enable the usage of the hybrid memory system, which outperforms cache-based systems by an speedup of 38% and an energy reduction of 27%. [ABSTRACT FROM AUTHOR]

We propose algorithms for distributing the classifier rules to two ternary content addressable memories (TCAMs) and for incrementally updating the TCAMs. The performance of our scheme is compared against the prevalent scheme of storing classifier rules in a single TCAM in priority order. Our scheme results in an improvement in average lookup speed by up to 49% and an improvement in update performance by up to 3.84 times in terms of the number of TCAM writes. [ABSTRACT FROM AUTHOR]

Transaction-level modeling (TLM) has become the de-facto reference modeling style for system-level design and verification of embedded systems. It allows designers to implement high-level communication protocols for simulations up to 1000 \times faster than at register-transfer level (RTL). To guarantee interoperability between TLM IP suppliers and users, designers implement the TLM communication protocols by relying on a reference standard, such as the standard OSCI for SystemC TLM. Functional correctness of such protocols as well as their compliance to the reference TLM standard are usually verified through user-defined testbenches, whose high quality and completeness play a key role for an efficient TLM design and verification flow. This article presents a methodology to apply mutation analysis, a technique applied in literature for SW testing, for measuring the testbench quality in verifying TLM protocols. In particular, the methodology aims at (i) qualifying the testbenches by considering both the TLM protocol correctness and their compliance to a defined standard (i.e., OSCI TLM), (ii) optimizing the simulation time during mutation analysis by avoiding mutation redundancies, and (iii) driving the designers in the testbench improvement. Experimental results on benchmarks of different complexity and architectural characteristics are reported to analyze the methodology applicability. [ABSTRACT FROM AUTHOR]

We consider Internet-based master-worker computations, where a master processor assigns, across the Internet, a computational task to a set of untrusted worker processors, and collects their responses. Examples of such computations are the "@homeâ' projects such as SETI. In this work, various worker behaviors are considered. Altruistic workers always return the correct result of the task, malicious workers always return an incorrect result, and rational workers act based on their self-interest. In a massive computation platform, such as the Internet, it is expected that all three type of workers coexist. Therefore, in this work, we study Internet-based master-worker computations in the presence of malicious, altruistic, and rational workers. A stochastic distribution of the workers over the three types is assumed. In addition, we consider the possibility that the communication between the master and the workers is not reliable, and that workers could be unavailable. Considering all the three types of workers renders a combination of game-theoretic and classical distributed computing approaches to the design of mechanisms for reliable Internet-based computing. Indeed, in this work, we design and analyze two algorithmic mechanisms to provide appropriate incentives to rational workers to act correctly, despite the malicious workers' actions and the unreliability of the communication. Only when necessary, the incentives are used to force the rational players to a certain equilibrium (which forces the workers to be truthful) that overcomes the attempt of the malicious workers to deceive the master. Finally, the mechanisms are analyzed in two realistic Internet-based master-worker settings, a SETI-like one and a contractor-based one, such as Amazon's mechanical turk. We also present plots that illustrate the tradeoffs between reliability and cost, under different system parameters. [ABSTRACT FROM AUTHOR]

We address pairwise and (for the first time) triple key establishment problems in wireless sensor networks (WSN). Several types of combinatorial designs have already been applied in key establishment. A $(BIBD(v,b,r,k,\lambda ))$ (or $(t-(v,b,r,k,\lambda ))$ design) can be mapped to a sensor network, where $(v)$ represents the size of the key pool, $(b)$ represents the maximum number of nodes that the network can support, and $(k)$ represents the size of the key chain. Any pair (or $(t)$-subset) of keys occurs together uniquely in exactly $(\lambda)$ nodes; $(\lambda = 2)$ and $(\lambda = 3)$ are used to establish unique pairwise or triple keys. We use several known constructions of designs with $(\lambda =2)$, to predistribute keys in sensors. We also describe a new construction of a design called strong Steiner trade and use it for pairwise key establishment. To the best of our knowledge, this is the first paper on application of trades to key distribution. Our scheme is highly resilient against node capture attacks (achieved by key refreshing) and is applicable for mobile sensor networks (as key distribution is independent on the connectivity graph), while preserving low storage, computation and communication requirements. We introduce a novel concept of triple key distribution, in which three nodes share common keys, and discuss its application in secure forwarding, detecting malicious nodes and key management in clustered sensor networks. We present a polynomial-based and a combinatorial approach (using trades) for triple key distribution. We also extend our construction to simultaneously provide pairwise and triple key distribution scheme, and apply it to secure data aggregation. [ABSTRACT FROM AUTHOR]

As new transport protocols are being proposed and standardized, the choice of the best communication service to be used by applications for delivering their data when distributed is becoming too complex. Application developers need much knowledge on "how the protocol worksâ to decide whether or not it can be used to fulfill their requirements. Moreover, the performance of the service provided by a given communication protocol is highly dependent on the network context. The Autonomic Transport Protocol presented in this paper is aware of the application requirements and uses learning techniques to adapt the service it provides to best satisfy these requirements as the network conditions vary. [ABSTRACT FROM AUTHOR]

New applications based on cloud computing, such as data synchronization for large chain departmental stores and bank transaction records, require very high-speed data transport. Although a number of high-bandwidth networks have been built, existing transport protocols or their variants over such networks cannot fully exploit the network bandwidth. Our experiments show that the fixed-size application level buffer employed in the receiver side is a major cause of this deficiency. A buffer that is either too small or too large impairs the transfer performance. Due to the varied natures of network conditions and of real-time packet processing (i.e., consuming) speed at the receiver, it is important to ensure that the buffer size is dynamically adjusted according to the perceived execution situation during runtime. In this paper, we propose Rada, a dynamic receiving buffer adaptation scheme for high-speed data transfer. Rada employs an exponential moving average aided scheme to quantify the data arrival rate and consumption rate in the buffer. Based on these two rates, we develop a linear aggressive increase conservative decrease scheme to adjust the buffer size dynamically. Moreover, a weighted mean function is employed to make the adjustment adaptive to the available memory in the receiver. Theoretical analysis is provided to demonstrate the rationale and parameter bounds of Rada. The performance of Rada is also theoretically compared with potential alternatives. We implement Rada in a Linux platform and extensively evaluate its performance in a variety of scenarios. Experimental results conform to the theoretical results, and show that Rada outperforms the static buffer scheme in terms of throughput, memory footprint, and fairness. [ABSTRACT FROM AUTHOR]

File replication is widely used in structured P2P systems to avoid hot spots in servers and enhance file availability. The number of replicas and replication distance affect the file replication cost. These two elements and the replica update frequency determined in the file replication stage also affect the cost of subsequent consistency maintenance. However, most existing file replication protocols focus on improving file lookup efficiency without considering its cost and its subsequent influence on consistency maintenance. This paper studies the problem about how a server chooses files to replicate and where to replicate files to achieve low cost in both file replication and consistency maintenance stages without compromising the effectiveness of file replication. This paper presents a lightweight and Cooperative multifactOr considered file Replication Protocol (CORP) to achieve this goal. CORP simultaneously takes into account multiple factors including file popularity, update rate, node available capacity, file load, and node locality, aiming to minimize the number of replicas, update frequency, and replication distance. CORP also dynamically adjusts the number of replicas based on ever-changing file popularity and visit pattern. Extensive experimental results from simulation and PlanetLab real-world testbed demonstrate the efficiency and effectiveness of CORP in comparison with other file replication protocols. It dramatically reduces the overhead of both file replication and consistency maintenance. In addition, it exhibits high adaptiveness to skewed lookups and yields significant improvement in reducing overloaded nodes. Specifically, compared to the other replication protocols, CORP can reduce more than 71 percent of file replicas, 84 percent of overloaded nodes, 94 percent of consistency maintenance cost, and 72 percent of file replication and consistency maintenance latency. [ABSTRACT FROM AUTHOR]

Recent years have seen the emergence of wireless cyber-physical systems that must support real-time queries of physical environments through wireless sensor networks. This paper proposes Real-Time Query Scheduling (RTQS), a novel approach to conflict-free transmission scheduling for real-time queries in wireless sensor networks. First, we show that there is an inherent tradeoff between latency and real-time capacity in query scheduling. We then present three new real-time schedulers. The nonpreemptive query scheduler supports high real-time capacity but cannot provide low response times to high-priority queries due to priority inversions. The preemptive query scheduler eliminates priority inversions at the cost of reduced capacity. The slack stealing query scheduler combines the benefits of the preemptive and nonpreemptive schedulers to improve the capacity while meeting the end-to-end deadlines of queries. We provide schedulability analysis for each scheduler. The analysis and advantages of our approach are validated through NS2 simulations. [ABSTRACT FROM AUTHOR]

When assigning personal keys, stateful multicast key distribution (MKD) protocols usually rely on some type of dynamic group access structure which helps achieve a better tradeoff among storage, communication, and computation overheads. However, there exist some stateful MKD protocols whose personal key assignments are based on two static group access structures called Dual Hash Chain (DHC) and Binary Hash Tree (BHT). We introduce two new types of group access structures called Dual Homomorphic One-way Function Chain (D-HOFC) and Top-Down Homomorphic One-way Function Tree (TD-HOFT). Both can be regarded as dynamic counterparts of DHC and BHT, respectively. Our research motivation is to investigate what benefits these two new dynamic structures will bring for MKD protocols compared with their static counterparts. Using D-HOFC, we propose a time-based MKD protocol that counters the rejoining member attack on a DHC-based protocol, and a stateful user-based MKD protocol that has a lower computational overhead for Group Controller (GC) than the DHC-based protocol. Using TD-HOFT, we design a stateful user-based MKD protocol that outperforms the original EKT protocol. Performance comparisons and experiment results show that our protocols based on dynamic structures have their own advantages compared with those based on the corresponding static counterparts. [ABSTRACT FROM PUBLISHER]

Channel assignment is a crucial problem for wireless networks, especially for noncooperative wireless networks, in which nodes are selfish. While there have been a few studies of noncooperative, multiradio channel assignment, most existing studies are restricted to single collision domains only. In this paper, we study the design of incentive-compatible protocols for noncooperative, multiradio channel assignment in multiple collision domains. First, we show the necessity of designing incentive-compatible protocols for this problem. Specifically, we show that, if no incentive-compatible protocol is deployed, Nash Equilibria (NEs) may have undesired properties, such as Pareto suboptimality and low throughput. To prevent the system from converging to the NEs with undesired properties, we propose an incentive-compatible protocol for channel assignment in multiple collision domains. We rigorously show that our protocol guarantees that the system converges to NEs that are Pareto-optimal and have the maximum system-wide throughput. Our simulation results also verify that our protocols are effective in ensuring that the system converges to the desired NEs. [ABSTRACT FROM AUTHOR]

In this paper, we explore a new form of dissemination that arises in distributed, mission-critical applications called Flash Dissemination. This involves the rapid dissemination of rich information to a large number of recipients in a very short period of time. A key characteristic of Flash Dissemination is its unpredictability (e.g., natural hazards), but when invoked it must harness all possible resources to ensure timely delivery of information. Additionally, it must scale to a large number of recipients and perform efficiently in highly heterogeneous (data, network) and failure prone environments. We investigate a peer-based approach based on the simple principle of transferring dissemination load to information receivers using foundations from broadcast networks, gossip theory, and random networks. Gossip-based protocols are well known for being stateless, scalable, and fault-tolerant; however, their performance degrades as content size increases, because of the propagation of redundant gossip messages. In this paper, we propose Concurrent Random Expanding Walkers (CREW), a smart gossip protocol designed to maximize the speed of dissemination by transmitting data only as needed, and by exploiting both intra- and internode concurrency. CREW is designed to support both content and network heterogeneity and deal with transmission failures without sacrificing dissemination speed. We implemented CREW on top of a scalable middleware environment that allows for deployment across several platforms and developed optimizations without compromising on the stateless nature of CREW. We evaluated CREW empirically and compared it to optimized implementations of popular gossip and peer-based systems. Our experiments show that CREW significantly outperforms both traditional gossip and current large content dissemination systems while sustaining its performance in the presence of network errors. [ABSTRACT FROM AUTHOR]

A key aspect in the design of efficient multiprocessor systems is the cache coherence protocol. Although directory-based protocols constitute the most scalable approach, the limited size of the directory caches together with the growing size of systems may cause frequent evictions and, consequently, the invalidation of cached blocks, which jeopardizes system performance. Directory caches keep track of every memory block stored in processor caches in order to provide coherent access to the shared memory. However, a significant fraction of the cached memory blocks do not require coherence maintenance (even in parallel applications) because they are either accessed by just one processor or they are never modified. In this paper, we propose to deactivate the coherence protocol for those blocks that do not require coherence. This deactivation means directory caches do not have to keep track of noncoherent blocks, which reduces directory cache occupancy and increases its effectiveness. Since the detection of noncoherent blocks is carried out by the operating system, our proposal only requires minor hardware modifications. Simulation results show that, thanks to our proposal, directory caches can avoid the tracking of about 66 percent (on average) of the blocks accessed by a wide range of applications, thereby improving the efficiency of directory caches. This contributes either to shortening the runtime of parallel applications by 15 percent (on average) while keeping directory cache size or to maintaining performance while using directory caches 16 times smaller. [ABSTRACT FROM AUTHOR]

Today Radio Frequency Identification (RFID) technologies are applied in many fields for a variety of applications. Though bringing great productivity gains, RFID systems may cause new security and privacy threats to individuals or organizations. Therefore, it is important to protect the security of RFID systems and the privacy of RFID tag owners. Unfortunately, none of the existing solutions provide a complete defense against eavesdroppers who could monitor the communication between RFID readers and tags and recover the contents of tags. Based on our research, we propose two novel RFID backward channel protection protocols, namely dynamic bit encoding and optimized dynamic bit encoding. Our schemes are able to achieve high anonymity with limited communication overhead. Our extensive simulations show that both proposed schemes provide much stronger backward channel protection than existing techniques. In addition, analytical models were created and validated through comparisons with simulation results. [ABSTRACT FROM AUTHOR]

In large-scale Wireless Sensor Networks (WSNs), leveraging data sinks' mobility for data gathering has drawn substantial interests in recent years. Current researches either focus on planning a mobile sink's moving trajectory in advance to achieve optimized network performance, or target at collecting a small portion of sensed data in the network. In many application scenarios, however, a mobile sink cannot move freely in the deployed area. Therefore, the precalculated trajectories may not be applicable. To avoid constant sink location update traffics when a sink's future locations cannot be scheduled in advance, we propose two energy-efficient proactive data reporting protocols, SinkTrail and SinkTrail-S, for mobile sink-based data collection. The proposed protocols feature low-complexity and reduced control overheads. Two unique aspects distinguish our approach from previous ones: 1) we allow sufficient flexibility in the movement of mobile sinks to dynamically adapt to various terrestrial changes; and 2) without requirements of GPS devices or predefined landmarks, SinkTrail establishes a logical coordinate system for routing and forwarding data packets, making it suitable for diverse application scenarios. We systematically analyze the impact of several design factors in the proposed algorithms. Both theoretical analysis and simulation results demonstrate that the proposed algorithms reduce control overheads and yield satisfactory performance in finding shorter routing paths. [ABSTRACT FROM AUTHOR]

As Internet and information technology have continued developing, the necessity for fast packet processing in computer networks has also grown in importance. All emerging network applications require deep packet classification as well as security-related processing and they should be run at line rates. Hence, network speed and the complexity of network applications will continue increasing and future network processors should simultaneously meet two requirements: high performance and high programmability. We will show that the performance of single processors will not be sufficient to support future demands. Instead, we will have to turn to multicore processors, which can exploit the parallelism in network workloads. In this paper, we focus on the cache coherence protocols which are central to the design of multicore-based network processors. We investigate the effects of two main categories of various cache coherence protocols with several network workloads on multicore processors. Our simulation results show that token protocols have a significantly higher performance than directory protocols. With an 8-core configuration, token protocols improves the performance compared to directory protocols by a factor of nearly 4 on average. [ABSTRACT FROM AUTHOR]

Although snoop-based coherence protocols provide fast cache-to-cache transfers with a simple and robust coherence mechanism, scaling the protocols has been difficult due to the overheads of broadcast snooping. In this paper, we propose a coherence filtering technique called subspace snooping, which stores the potential sharers of each memory page in the page table entry. By using the sharer information in the page table entry, coherence transactions for a page generate snoop requests only to the subset of nodes in the system. However, the coherence subspace of a page may evolve, as the phases of applications may change or the operating system may migrate threads to different nodes. To adjust subspaces dynamically, subspace snooping supports two different shrinking mechanisms, which remove obsolete nodes from subspaces. Among the two shrinking mechanisms, subspace snooping with safe shrinking can be integrated to any type of coherence protocols and network topologies, as it guarantees that a subspace always contains the precise sharers of a page. Speculative shrinking breaks the subspace superset property, but achieves better snoop reductions than safe shrinking. We evaluate subspace snooping with Token Coherence on unordered mesh networks. Subspace snooping reduces 58 percent of snoops on average for a set of parallel scientific and server workloads, and 87 percent for our multiprogrammed workloads. [ABSTRACT FROM PUBLISHER]

We address content discovery in wireless networks with infrastructure, where mobile nodes store, advertise, and consume content while Broker entities running on infrastructure devices let demand and offer meet. We refer to this paradigm as match-making, highlighting its features within the confines of the standard publish-and-subscribe paradigm. We study its performance in terms of success probability of a content query, a parameter that we strive to increase by acting as follows: 1) We design a credit-based scheme that makes it convenient for rational users to provide their content (thus discouraging free-riding behavior), and it guarantees them a fair treatment. 2) We increase the availability of either popular or rare content, through an efficient caching scheme. 3) We counter malicious nodes whose objective is to disrupt the system performance by not providing the content they advertise. To counter the latter as well as free riders, we introduce a feedback mechanism that enables a Broker to tell apart well- and misbehaving nodes in a very reliable manner, and to ban the latter. The properties of our match-making scheme are analyzed through game theory. Furthermore, via ns-3 simulations, we show its resilience to different attacks by malicious users and its good performance with respect to other existing solutions. [ABSTRACT FROM AUTHOR]

In this work, we assume a geographic area populated by tiny sensors, each perhaps no larger than a dime. In order to save their energy, the sensors spend most of their lifetime in sleep mode and wake up for short periods of time to participate in various tasks supportive of the overall mission of the network. We assume that the tasks to be performed stipulate QoS parameters expressed in terms of the minimum number of sensors that need to monitor their sensing area. Since only awake sensors participate in tasks, the Effective Sensor Density (ESD), defined as the density of awake sensors, is an important network parameter that obviously depends on the sleep schedules adopted in the network. The first main contribution of this work is to provide a mathematical analysis of ESD from the perspective of the monitored events. We also provide design guidelines to determine deployment-time sensor density and an associated sleep schedule that probabilistically keeps the ESD at a level needed by QoS requirements. We also propose a fully distributed sleep schedule which adaptively adjusts the duty cycles of sensors within the same sensing area based on the relative difference in their remaining energy budget. The main advantage of the proposed adaptive scheme is to balance energy consumption among sensors, thus promoting the functional longevity of the sensor network without adversely affecting the ESD. [ABSTRACT FROM AUTHOR]

The IEEE P1687 (IJTAG) standard proposal aims at providing a standardized interface between the IEEE Standard 1149.1 test access port (TAP) and on-chip embedded test, debug and monitoring logic (instruments), such as scan chains and temperature sensors. A key feature in P1687 is to include Segment Insertion Bits (SIBs) in the scan path to allow flexibility both in designing the instrument access network and in scheduling the access to instruments. This paper presents algorithms to compute the overall access time (OAT) for a given P1687 network. The algorithms are based on analysis for flat and hierarchical network architectures, considering two access schedules, i.e., concurrent schedule and sequential schedule. In the analysis, two types of overhead are identified, i.e., network configuration data overhead and JTAG protocol overhead. The algorithms are implemented and employed in a parametric analysis and in experiments on realistic industrial designs. [ABSTRACT FROM AUTHOR]

Motivated by the strong demand for flash memory with enhanced reliability, this work attempts to achieve improved flash-memory endurance without substantially increasing overhead and without excessively modifying popular implementation designs such as the Flash Translation Layer protocol (FTL), NAND Flash Translation Layer protocol (NFTL), and Block-Level flash translation layer protocol (BL). A wear-leveling mechanism for moving data that are not updated is proposed to distribute wear-leveling actions over the entire physical address space, so that static or rarely updated data can be proactively moved and memory-space requirements can be minimized. The properties of the mechanism are then explored with various implementation considerations. A series of experiments based on a realistic trace demonstrates the significantly improved endurance of FTL, NFTL, and BL with limited system overhead. [ABSTRACT FROM AUTHOR]

Peer-to-peer (P2P) architectures are popular for tasks such as collaborative download, VoIP telephony, and backup. To maximize performance in the face of widely variable storage capacities and bandwidths, such systems typically need to shift work from poor nodes to richer ones. Similar requirements are seen in today's large data centers, where machines may have widely variable configurations, loads, and performance. In this paper, we consider the slicing problem, which involves partitioning the participating nodes into κ subsets using a one-dimensional attribute, and updating the partition as the set of nodes and their associated attributes change. The mechanism thus facilitates the development of adaptive systems. We begin by motivating this problem statement and reviewing prior work. Existing algorithms are shown to have problems with convergence, manifesting as inaccurate slice assignments, and to adapt slowly as conditions change. Our protocol, Sliver, has provably rapid convergence, is robust under stress and is simple to implement. We present both theoretical and experimental evaluations of the protocol. [ABSTRACT FROM AUTHOR]

Abstract--Open distributed systems are typically composed by an unknown number of processes running in heterogeneous hosts.. Their communication often requires tolerance to temporary disconnections and security against malicious actions. Tuple spaces are a well-known coordination model for this kind of systems. They can support communication that is decoupled both in time and space. There are currently several implementations of distributed fault-tolerant tuple spaces but they are not Byzantine-resilient, i.e., they do not provide a correct service if some replicas are attacked and start to misbehave. This paper presents an efficient implementation of a Linearizable Byzantine fault-tolerant Tuple Space (LBTS) that uses a novel Byzantine quorum systems replication technique in which most operations are implemented by quorum protocols while stronger operations are implemented by more expensive protocols based on consensus. LBTS is linearizable and wait-free, showing interesting performance gains when compared to a similar construction based on state machine replication. [ABSTRACT FROM AUTHOR]

In diversity combining automatic repeat request (ARQ), erroneous packets are combined together forming a single, more reliable, packet. In this paper, we give a diversity combining scheme for the m-ary unidirectional channel. A system using the given scheme with a t-unidirectional error detecting code is able to correct up to Emax = t/2 unidirectional errors. Simulation results show that the underlined diversity combining protocol significantly increases the channel throughput over plain ARQ. To use the given scheme, the decoder should be able to decide the error type (increasing or decreasing). Hence, we give simple techniques to make this decision for various unidirectional error detecting codes. [ABSTRACT FROM AUTHOR]

In this paper, we consider security-related and energy efficiency issues in multihop wireless networks. We start our work from the observation, known in the literature, that shortest path routing creates congested areas in multihop wireless networks. These areas are critical—they generate both security and energy efficiency issues. We attack these problems and set out routing in outer space, a new routing mechanism that transforms any shortest path routing protocol (or approximated versions of it) into a new protocol that does not create congested areas, does not have the associated security-related issues, and does not encourage selfish positioning. Moreover, the network is more energy efficient than the same network using the original routing protocol (in spite of using more energy globally) and dies more gracefully. We also describe applications of our idea to mobility and to a security protocol for the detection of node replication attacks. [ABSTRACT FROM AUTHOR]

The establishment of a localization system is an important task in wireless sensor networks. Due to the geographical correlation between sensed data, location information is commonly used to name the gathered data and address nodes and regions in data dissemination protocols. In general, to estimate its location, a node needs the position information of at least three reference points (neighbors that know their positions). In this work, we propose a different scheme in which only two reference points are required in order to estimate a position. To choose between the two possible solutions of an estimate, we use the known direction of the recursion. This approach leads to a recursive localization system that works with low-density networks (increasing by 40 percent the number of nodes with estimates in some cases), reduces the position error by almost 30 percent, requires 37 percent less processor resources to estimate a position, uses fewer beacon nodes, and also indicates the node position error based on its distance to the recursion origin. No GPS-enabled node is required, since the recursion origin can be used as a relative coordinate system. The algorithm's evaluation is performed by comparing it with a similar localization system; also, experiments are made to evaluate the impact of both systems in geographic algorithms. [ABSTRACT FROM AUTHOR]

Let G = (V, E, w) be a simple digraph, in which all edge weights are nonnegative real numbers. Let G' be obtained from G by an application of a set of edge weight updates to G. Let s ∈ V and let Ts and T's be Shortest Path Trees (SPTs) rooted at s in G and G', respectively. The Dynamic Shortest Path (DSP) problem is to compute T's from Ts. Existing work on this problem focuses on either a single edge weight change or multiple edge weight changes in which some of them are incorrect or are not optimized. We correct and extend a few state-of-the-art dynamic SPT algorithms to handle multiple edge weight updates. We prove that these algorithms are correct. Dynamic algorithms may∙not outperform static algorithms all the time. To evaluate the proposed dynamic algorithms, we compare them with the well-known static Dijkstra algorithm. Extensive experiments are conducted with both real-life and artificial data sets. The experimental results suggest the most appropriate algorithms to be used under different circumstances. [ABSTRACT FROM AUTHOR]

With the advent of powerful network processors (NPs) in the market, many computation-intensive tasks such as routing table lookup, classification, IPSec, and multimedia transcoding can now be accomplished more easily in a router. An NP consists of a number of on-chip processors to carry out packet level parallel processing operations. Ensuring good load balancing among the processors increases throughput. However, such multiprocessing also gives rise to increased out-of-order departure of processed packets. in this paper, we first propose an Ordered Round-Robin (ORR) scheme to schedule packets in a heterogeneous NP assuming that the workload is perfectly divisible. The processed loads from the processors are ordered perfectly. We analyze the throughput and derive expressions for the batch size, scheduling time, and maximum number of schedulable processors. To effectively schedule variable length packets in an NP, we propose a Pàcketized ORR (P-ORR) scheme by applying a combination of deficit round-robin (DRR) and surplus round-robin (SRR) schemes. We extend the algorithm to handle multiple flows based on a fair scheduling of flows depending on their reservations. Extensive sensitivity results are provided through analysis and simulation to show that the proposed algorithms satisfy both the load balancing and in-order requirements for parallel packet processing. [ABSTRACT FROM AUTHOR]