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Many applications that utilise wireless sensor networks (WSNs) require essentially secure communication. However, WSNs suffer from some inherent weaknesses because of restricted communication and hardware capabilities. Key management is the crucial important building block for all security goals in WSNs. Most existing researches tried to assign keys assuming homogeneous network architecture. Recently, a few key management models for heterogeneous WSNs have been proposed. In this study, the authors propose a dynamic key management framework based on elliptical curve cryptography and signcryption method for heterogeneous WSNs. The proposed scheme has network scalability and sensor node (SN) mobility especially in liquid environments. Moreover, both periodic authentication and a new registration mechanism are proposed through prevention of SN compromise. The authors analyse some of the more seminal hierarchical heterogeneous WSN key management schemes and compare them with the proposed scheme. On comparing the proposed scheme with the more seminal hierarchical heterogeneous WSN key management schemes, the proposed framework individually proves to be better in terms of communication, computation and key storage. [ABSTRACT FROM AUTHOR]

A source model including four terminals is considered, where three simultaneously generating three types of keys are intended. Terminals 1, 2 and 3 wish to share a common key, the secret key, which should be kept secret from terminal 4 and simultaneously terminals 1 and 2 intend to share a private key with terminal 3, which should be kept secret from each other. Also, all the keys should be concealed from terminal 4 (the external wiretapper). The authors assume that all terminals including the external wiretapper have access to distinct correlated i.i.d. sources; there is also a noiseless public channel with unlimited capacity among the terminals. The authors have investigated the model on two scenarios of key sharing depending on the direction of the public channel. Rate regions of the keys are derived. It is shown that in some special cases the inner and outer bounds of the capacity regions coincide and the capacity regions are derived. [ABSTRACT FROM AUTHOR]

New inner and outer bounds on the achievable compression-equivocation rate region for generalised secure data compression with side information are given that do not match in general. In this setup, two senders, Alice and Charlie intend to transmit information to Bob via channels with limited capacity so that he can reliably reconstruct their observations. The eavesdropper, Eve, has access to one of the channels at each instant and is interested in the source of the same channel at the time. Bob and Eve also have their own observations, which are correlated with Alice's and Charlie's observations. In this model, two equivocation and compression rates are defined with respect to the sources of Alice and Charlie. Furthermore, different special cases are discussed where the inner and outer bounds match. Our model covers the previously obtained results as well. [ABSTRACT FROM AUTHOR]

The discrete memoryless state-dependent relay channel (SD-RC) is considered in this study. Two main cases are investigated: SD-RC with non-causal channel state information (CSI) and SD-RC with causal CSI. In each case, the SD-RC with partial CSI at the source and the relay is considered. As special cases it includes three different situations in which perfect CSI is available: (i) only at the source, (ii) only at the relay and (iii) both at the source and the relay. For the non-causal situation, the authors establish lower bound on capacity (achievable rate) of the SD-RC, using Gel'fand-Pinsker coding at the nodes informed of CSI and compress-and-forward (CF) strategy at the relay. Using the Shannon's strategy and CF relaying, the authors derive lower bound on capacity of SD-RC in the causal case. Furthermore, in order to compare their derived bounds with the previously obtained results, which are based on the decode-and-forward (DF) strategy, the authors consider general Gaussian relay channel (RC) with additive independent and identically distributed Gaussian state and noise, and obtain lower bounds on capacity for the cases in which perfect CSI is available non-causally at the source or at the relay. They also present cases in which their lower bounds outperform DF-based bounds, and can achieve rates close to the upper bound. For causal case, a numerical example of the binary fading Gaussian RC with additive noise is provided. [ABSTRACT FROM AUTHOR]

The authors consider the problem of broadcast-relay-networks with two cooperative relays. There are a transmitter, two relays and two receivers in the network. The message of the transmitter intended to the receivers has common and private parts. The relays fully cooperate with each other and with the transmitter to send the common part of the message, whereas the private parts of the message are sent through the direct links between the transmitter and receivers. The authors found an achievable rate region for this network by using the symmetric relaying strategy. In this strategy, each relay completely decodes the message of other relay. In the proof the authors took advantage of regular encoding/sliding window decoding at relays and simultaneous backward decoding analysis at receivers. Marton's broadcast code construction is used at the transmitter to split the rate between the users. Three special cases of achievable rate region are shown: (i) Kramer's achievable rate region for broadcast relay channel; (ii) Ghabeli's achievable rate for symmetric two-relay network; and (iii) Marton's achievable rate region for broadcast channel with common message. The additive white Gaussian noise model is also considered and the achievable rate region of Gaussian network is discussed. [ABSTRACT FROM AUTHOR]

Gastpar and Vetterli named the ad hoc networks with one randomly selected source-destination pair as relay networks, and they suggested using arbitrary network coding in order to increase the overall efficiency. Here, the relay network is investigated with two relays, no interference and a new achievable rate is obtained using a new network coding (decode-and-broadcast). The obtained achievable rate (i) gives the lower bound for general relay channel, obtained by Cover and El Gamal, but with a slight difference owing to no interference assumption at the receiver, (ii) includes the one relay rates of a two-level relay channel studied by Gupta and Kumar using point-to-point coding, (iii) includes the rates of two-relay Aref network and other special two-relay networks, (iv) meets the max-flow min-cut upper bound under certain additional assumptions resulting in certain capacity theorems that include the related previous capacities, (v) is validated by its consistency with previous results relevant to special cases of broadcast channels. [ABSTRACT FROM AUTHOR]

The authors indicate the dependence between the inputs of the relay channel with one auxiliary random variable as Cover, El-Gamal and Salehi have done for the multiple access channel with arbitrarily correlated sources. Then, by considering broadcast and multiple access sub-channels in the relay channel, the authors describe the essential role of the relay with special Markovity conditions on the auxiliary random variable and channel input–outputs, and unify most of known capacity theorems into one capacity theorem. The capacity theorem potentially may be applicable to a more general class of relay channels including at least the relay channels with known capacity. [ABSTRACT FROM AUTHOR]

Partial decoding scheme is a scheme in which each relay decodes only part of the transmitted message. Obviously, the achievable rates proposed by the partial decoding scheme subsume the achievable rates proposed by the full decoding scheme. The other motivation of using partial decoding scheme is that there are some special classes of relay networks such as semi-deterministic and orthogonal relay networks such that their capacities are obtained via this scheme. The authors propose a comprehensive partial decoding scheme based on regular encoding/sliding window decoding analysis to propose a new achievable rate for two-level relay networks. In contrast with the previously proposed methods, here the authors consider all possible partial decoding states that can occur between the different parts of the messages of the source and the relays in a two-level relay network. In this way, the common and private parts of the message transmitted by the source are defined to be decoded by the appropriate relays. Moreover, in the proof, the authors take advantage of regular encoding/sliding window decoding scheme that has superiorities to regular encoding/backward decoding and irregular encoding/random partitioning, in having less delay and yielding higher rates, respectively. [ABSTRACT FROM AUTHOR]

A secure channel coding (joint encryption-channel coding) scheme provides both data security and reliability in one combined process to achieve faster processing and/or more efficient implementation. The issue of using quasi-cyclic low-density parity-check (QC-LDPC) codes in a symmetric-key secure channel coding scheme is addressed. A set of this class of LDPC codes has recently been recommended by the NASA Goddard Space Flight Center for near-earth and deep-space communications. The proposed scheme provides an efficient error performance, an acceptable level of security and a low-complexity practicable implementation. The results indicate that the proposed scheme can efficiently employ large QC-LDPC codes to achieve a relatively smaller secret-key size to be exchanged by the sender and the receiver, and higher information rates in comparison with the previous symmetric-key McEliece-like schemes. Simulation results indicate that there is no trade-off between the error performance and the security level of the proposed scheme unlike that of the previous ones. These characteristics make the proposed scheme suitable for high-speed communications, such as satellite communication systems. [ABSTRACT FROM AUTHOR]

Symmetric relaying is a method of relaying in which the relays can decode the message of other relays in the network in addition to the source message. In this paper an achievable rate is presented for a symmetric two-relay network based on partial decoding. The strategy make use of familiar techniques such as product binning, regular encoding/sliding window decoding and regular encoding/backward decoding. The proposed rate is shown to subsume the previously proposed rate for feed-forward relay network based on decode-and-forward. This rate is also used to establish the capacity of a generalisation of Aref network called ‘semi-deterministic relay network with no interference at the relays’ and independent relay inputs. [ABSTRACT FROM AUTHOR]

Both security and error control coding are very extensive subjects, each with a variety of sub-disciplines. A secure channel coding (joint encryption-channel coding) scheme provides both data secrecy and data reliability in one process to combat problems in an insecure and unreliable channel. In this paper, an adaptive secure channel coding scheme based on serial or parallel concatenated turbo codes is developed. Recent results indicate that the turbo principle delivers near-to-optimal strategies for the channel coding. Reliability and security are achieved by adapting the pseudo-random puncturing strategy to the conditions of the noisy channel. Simulation results show the relevance and superior performance of the proposed scheme at all signal-to-noise ratio levels. [ABSTRACT FROM AUTHOR]