Elena Dubrova

A SAT-Based Algorithm for Finding Attractors in Synchronous Boolean Networks

This paper addresses the problem of finding attractors in synchronous Boolean networks. The existing Boolean decision diagram-based algorithms have limited capacity due to the excessive memory requirements of decision diagrams. The simulation-based algorithms can be applied to larger networks, however, they are incomplete. We present an algorithm, which uses a SAT-based bounded model checking to find all attractors in a Boolean network. The efficiency of the presented algorithm is evaluated by analyzing seven networks models of real biological processes, as well as 150,000 randomly generated Boolean networks of sizes between 100 and 7,000. The results show that our approach has a potential to handle an order of magnitude larger models than currently possible.

Design of a terminal solution for integration of in-home health care devices and services towards the Internet-of-Things

In-home health care services based on the Internet-of-Things are promising to resolve the challenges caused by the ageing of population. But the existing research is rather scattered and shows lack of interoperability. In this article, a business-technology co-design methodology is proposed for cross-boundary integration of in-home health care devices and services. In this framework, three key elements of a solution (business model, device and service integration architecture and information system integration architecture) are organically integrated and aligned. In particular, a cooperative Health-IoT ecosystem is formulated, and information systems of all stakeholders are integrated in a cooperative health cloud as well as extended to patients’ home through the in-home health care station (IHHS). Design principles of the IHHS includes the reuse of 3C platform, certification of the Health Extension, interoperability and extendibility, convenient and trusted software distribution, standardised and secured electrical health care record handling, effective service composition and efficient data fusion. These principles are applied to the design of an IHHS solution called iMedBox. Detailed device and service integration architecture and hardware and software architecture are presented and verified by an implemented prototype. The quantitative performance analysis and field trials have confirmed the feasibility of the proposed design methodology and solution.

A Transformation From the Fibonacci to the Galois NLFSRs

Conventional nonlinear feedback shift registers (NLFSRs) use the Fibonacci configuration in which the feedback is applied to the last bit only. In this paper, we show how to transform a Fibonacci NLFSR into an equivalent NLFSR in the Galois configuration, in which the feedback can be applied to every bit. Such a transformation can potentially reduce the depth of the circuits implementing feedback functions, thus decreasing the propagation time and increasing the throughput.

Ring oscillator physical unclonable function with multi level supply voltages

In this paper we introduce a new type of Ring Oscillator PUF (RO-PUF) in which the inverters composing the ring oscillators can be supplied by independent voltages. This new RO-PUF can improve the reliability of the PUF in case of temperature variations.

Kauffman networks: analysis and applications

A Kauffman network is an abstract model of gene regulatory networks. Each gene is represented by a vertex. An edge from one vertex to another implies that the former gene regulates the latter. Statistical features of Kauffman networks match the characteristics of living cells. The number of cycles in the networks state space, called attractors, corresponds to the number of different cell types. The attractors length corresponds to the cell cycle time. The sensitivity of attractors to different kinds of disturbances, modeled by changing a network connection, the state of a vertex, or the associated function, reflects the stability of the cell to damage, mutations and virus attacks. In order to evaluate attractors, their number and lengths have to be computed. This problem is the major open problem related to Kauffman networks. Available algorithms can only handle networks with less than a hundred vertices. The number of genes in a cell is often larger. In this paper, we present a set of efficient algorithms for computing attractors in large Kauffman networks. The resulting software package is hoped to be of assistance in understanding the principles of gene interactions and discovering a computing scheme operating on these principles.

A Scalable Method for Constructing Galois NLFSRs With Period

A method for constructing n-stage Galois NLFSRs with period 2n-1 from n-stage maximum length LFSRs is presented. Nonlinearity is introduced into state cycles by adding a nonlinear Boolean function to the feedback polynomial of the LFSR. Each assignment of variables for which this function evaluates to 1 acts as a crossing point for the LFSR state cycle. The effect of nonlinearity is cancelled and state cycles are joined back by adding a copy of the same function to a later stage of the register. The presented method requires no extra time steps and it has a smaller area overhead compared to the previous approaches based on cross-join pairs. It is feasible for large n.

2^n-1

Non-linear feedback shift registers (NLFSRs) have been proposed as an alternative to Linear Feedback Shift Registers (LFSRs) for generating pseudo-random sequences for stream ciphers. In this paper, we introduce (n,k)-NLFSRs which can be considered a generalization of the Galois type of LFSR. In an (n,fc)-NLFSR, the feedback can be taken from any of the n bits, and the next state functions can be any Boolean function of up to k variables. Our motivation for considering this type NLFSRs is that their Galois configuration makes it possible to compute each next state function in parallel, thus increasing the speed of output sequence generation. Thus, for stream cipher application where the encryption speed is important, (n,k)-NLFSRs may be a better alternative than the traditional Fibonacci ones. We derive a number of properties of (n,k)- NLFSRs. First, we demonstrate that they are capable of generating output sequences with good statistical properties which cannot be generated by the Fibonacci type of NLFSRs. Second, we show that the period of the output sequence of an (n,k)-NLFSR is not necessarily equal to the length of the largest cycle of its states. Third, we compute the period of an (n,k)-NLFSR constructed from several parallel NLFSRs whose outputs are XOR-ed and show how to maximize this period. We also present an algorithm for estimating the length of cycles of states of (n,k)-NLFSRs which uses binary decision diagrams for representing the set of states and the transition relation on this set.

Using Cross-Join Pairs

The problem of efficient implementation of security mechanisms for advanced contactless technologies like RFID is gaining increasing attention. Severe constraints on resources such as area, power consumption, and production cost make the application of traditional cryptographic techniques to these technologies a challenging task. Non-Linear Feedback Shift Register (NLFSR)-based stream ciphers are promising candidates for cryptographic primitives for RFIDs because they have the smallest hardware footprint of all existing cryptographic systems. This paper presents a heuristic algorithm for constructing a fastest Galois NLFSR generating a given sequence. The algorithm takes an NLFSR in the Fibonacci configuration and transforms it to an equivalent Galois NLFSR which has the minimal delay. Our key idea is to find a best position for a given feedback connection without changing the positions of the other feedback connections. We use a technology dependent cost function which approximates the delay of an NLFSR after the technology mapping. The experimental results on 57 NLFSRs used in existing stream ciphers show that, on average, the presented algorithm allows us to decrease the delay by 25.5% as well as to reduce the area by 4.1%.

On analysis and synthesis of ( n, k )-non-linear feedback shift registers

The growing complexity of todays system designs requires fast and robust verification methods. Existing BDD, SAT or ATPG-based techniques do not provide sufficient solutions for many verification instances. Boolean function hashing is a probabilistic verification approach which can complement existing formal methods in a number of applications such as equivalence checking, biased random simulation, power analysis and power optimization. The proposed hashing technique is based on the arithmetic transform, which maps a Boolean function onto a probabilistic hash value for a given input assignment. The presented algorithm uses multiple-vertex dominators in circuit graphs to progressively simplify intermediate hashing steps. The experimental results on benchmark circuits demonstrate the robustness of our approach.

An algorithm for constructing a fastest Galois NLFSR generating a given sequence

Binary machines are a generalization of Feedback Shift Registers (FSRs) in which both, feedback and feedforward, connections are allowed and no chain connection between the register stages is required. In this paper, we present an algorithm for synthesis of binary machines with the minimum number of stages for a given degree of parallelization. Our experimental results show that for sequences with high linear complexity such as complementary, Legendre, or truly random, parallel binary machines are an order of magnitude smaller than parallel FSRs generating the same sequence. The presented approach can potentially be of advantage for many applications including wireless communication, cryptography, and testing.