Joanne Fuller, PhD

The occurrence of extreme movements in the spot price of electricity represents a significant source of risk to retailers. A range of approaches have been considered with respect to modelling electricity prices; these models, however, have relied on time-series approaches, which typically use restrictive decay schemes placing greater weight on more recent observations. This study develops an alternative, semi-parametric method for forecasting, which uses state-dependent weights derived from a… Show more

The occurrence of extreme movements in the spot price of electricity represents a significant source of risk to retailers. A range of approaches have been considered with respect to modelling electricity prices; these models, however, have relied on time-series approaches, which typically use restrictive decay schemes placing greater weight on more recent observations. This study develops an alternative, semi-parametric method for forecasting, which uses state-dependent weights derived from a kernel function. The forecasts that are obtained using this method are accurate and therefore potentially useful to electricity retailers in terms of risk management. Show less

A dislike of math is a common problem at all levels of education, but particularly at the tertiary level, this dislike has often translated into a deep-seated fear due to the prolonged failure to master core skills, as well as potential avoidance of such education. This is especially evident for Business studies students, whom in many instances perceive math as being completely redundant to their studies. The question therefore arises as to what level of math skill a typical business studies… Show more

A dislike of math is a common problem at all levels of education, but particularly at the tertiary level, this dislike has often translated into a deep-seated fear due to the prolonged failure to master core skills, as well as potential avoidance of such education. This is especially evident for Business studies students, whom in many instances perceive math as being completely redundant to their studies. The question therefore arises as to what level of math skill a typical business studies student will possess as they enter the tertiary environment, and whether there are any common deficiencies that we can identify with a view to tackling the problem. This presentation will focus on the results of a study, conducted over several years, designed to measure the level of math ability of first year business students as they enter a compulsory data analysis subject. It will be shown that there are several areas of concern where students do not possess the requisite knowledge required for successful completion of the subject. Show less

The advancement of online teaching environments during the past several years presents an exciting opportunity to extend existing teaching methodologies. The software package known as Elluminate is one example of a virtual classroom, facilitating the provision of real time interaction, collaboration and group meetings. This paper will examine the use of Elluminate in the teaching of large classes. The use of such technology for large classes is of particular interest, as large classes are… Show more

The advancement of online teaching environments during the past several years presents an exciting opportunity to extend existing teaching methodologies. The software package known as Elluminate is one example of a virtual classroom, facilitating the provision of real time interaction, collaboration and group meetings. This paper will examine the use of Elluminate in the teaching of large classes. The use of such technology for large classes is of particular interest, as large classes are often, unfairly, associated with a reputation for being impersonal as well as notions of conveyor belt learning. In this paper the potential to extend teaching and learning opportunities using Elluminate, in the context of large classes, will be explored. It will be shown that the use of technology such as Elluminate can assist in providing students with a more flexible means of accessing academic support, as well as allowing for a customised delivery of course content so as to focus learning outcomes. Show less

In this paper we investigate the heuristic construction of bijective s-boxes that satisfy a wide range of cryptographic criteria including algebraic complexity, high nonlinearity, low autocorrelation and have none of the known weaknesses including linear structures, fixed points or linear redundancy. We demonstrate that the power mappings can be evolved (by iterated mutation operators alone) to generate bijective s-boxes with the best known tradeoffs among the considered criteria. The s-boxes… Show more

In this paper we investigate the heuristic construction of bijective s-boxes that satisfy a wide range of cryptographic criteria including algebraic complexity, high nonlinearity, low autocorrelation and have none of the known weaknesses including linear structures, fixed points or linear redundancy. We demonstrate that the power mappings can be evolved (by iterated mutation operators alone) to generate bijective s-boxes with the best known tradeoffs among the considered criteria. The s-boxes found are suitable for use directly in modern encryption algorithms. Show less

This paper presents Dragon, a new stream cipher constructed using a single word based non-linear feedback shift register and a non-linear filter function with memory. Dragon uses a variable length key and initialisation vector of 128 or 256 bits, and produces 64 bits of keystream per iteration. At the heart of Dragon are two highly optimised 8 × 32 s-boxes. Dragon uses simple operations on 32-bit words to provide a high degree of efficiency in a wide variety of environments, making it highly… Show more

This paper presents Dragon, a new stream cipher constructed using a single word based non-linear feedback shift register and a non-linear filter function with memory. Dragon uses a variable length key and initialisation vector of 128 or 256 bits, and produces 64 bits of keystream per iteration. At the heart of Dragon are two highly optimised 8 × 32 s-boxes. Dragon uses simple operations on 32-bit words to provide a high degree of efficiency in a wide variety of environments, making it highly competitive when compared with other word based stream ciphers. The components of Dragon are designed to resist all known attacks. Show less

In this work we investigate the heuristic construction of bijective s-boxes that satisfy a wide range of cryptographic criteria including algebraic complexity, high nonlinearity, low autocorrelation and have none of the known weaknesses including linear structures, fixed points or linear redundancy. We demonstrate that the power mappings can be evolved (by iterated mutation operators alone) to generate bijective s-boxes with the best known tradeoffs among the considered criteria. The s-boxes… Show more

In this work we investigate the heuristic construction of bijective s-boxes that satisfy a wide range of cryptographic criteria including algebraic complexity, high nonlinearity, low autocorrelation and have none of the known weaknesses including linear structures, fixed points or linear redundancy. We demonstrate that the power mappings can be evolved (by iterated mutation operators alone) to generate bijective s-boxes with the best known tradeoffs among the considered criteria. The s-boxes found are suitable for use directly in modern encryption algorithms. Show less

In symmetric cryptology the resistance to attacks depends critically on the nonlinearity properties of the Boolean functions describing cipher components like Substitution boxes (S-boxes). Some of the most effective methods known to generate functions that satisfy multiple criteria are based on evolutionary heuristics. In this paper, we improve on these algorithms by employing an adaptive strategy. Additionally, using recent improvements in the understanding of these combinatorial structures… Show more

In symmetric cryptology the resistance to attacks depends critically on the nonlinearity properties of the Boolean functions describing cipher components like Substitution boxes (S-boxes). Some of the most effective methods known to generate functions that satisfy multiple criteria are based on evolutionary heuristics. In this paper, we improve on these algorithms by employing an adaptive strategy. Additionally, using recent improvements in the understanding of these combinatorial structures, we discover essential properties of the graph formed by affine equivalence classes of Boolean functions, which offers several advantages as a conceptual model for multiobjective seeking evolutionary heuristics. Finally, we propose the first major global cooperative effort to discover new bounds for cryptographic properties of Boolean functions. Show less

We present a new heuristic algorithm that efficiently generates Boolean Bent functions, which have desirable cryptographic properties including maximum nonlinearity. By using an evolutionary approach to design, we discover an easy way to find the algebraic normal forms of new bent functions. These algorithms run efficiently, making them suitable for engineering the components of modern symmetric encryption algorithms. In addition, we enable the algorithm to determine when new classes of bent… Show more

We present a new heuristic algorithm that efficiently generates Boolean Bent functions, which have desirable cryptographic properties including maximum nonlinearity. By using an evolutionary approach to design, we discover an easy way to find the algebraic normal forms of new bent functions. These algorithms run efficiently, making them suitable for engineering the components of modern symmetric encryption algorithms. In addition, we enable the algorithm to determine when new classes of bent functions have been discovered, by developing more a more effective approach to the equivalence class distinguishing problem. These results allow the efficient automated generation of many optimal Boolean functions that can be guaranteed to be affine non-equivalent, thus offering far more accurate classification of bent functions than previously available Show less

This paper reports the discovery of linear redundancy in the S-boxes of many ciphers recently proposed for standardisation (including Rijndael, the new AES). We introduce a new method to efficiently detect affine equivalence of Boolean functions, and hence we study the variety of equivalence classes existing in random and published S-boxes. This leads us to propose a new randomness criterion for these components. We present experimental data supporting the notion that linear redundancy is very… Show more

This paper reports the discovery of linear redundancy in the S-boxes of many ciphers recently proposed for standardisation (including Rijndael, the new AES). We introduce a new method to efficiently detect affine equivalence of Boolean functions, and hence we study the variety of equivalence classes existing in random and published S-boxes. This leads us to propose a new randomness criterion for these components. We present experimental data supporting the notion that linear redundancy is very rare in S-boxes with more than 6 inputs. Finally we discuss the impact this property may have on implementations, review the potential for new cryptanalytic attacks, and propose a new tweak for block ciphers that removes the redundancy. We also provide details of a highly nonlinear 8*8 non-redundant bijective S-box, which is suitable as a plug in replacement where required. Show less

In symmetric cryptology (which is an essential part of modern computer security), the resistance to attacks depends critically on the nonlinearity properties of the Boolean functions describing cipher components like S-boxes. Some of the most effective methods known to generate functions that satisfy multiple criteria are based on evolutionary heuristics. In this paper, we improve on these algorithms by employing an adaptive strategy. Additionally, using recent improvements in the understanding… Show more

In symmetric cryptology (which is an essential part of modern computer security), the resistance to attacks depends critically on the nonlinearity properties of the Boolean functions describing cipher components like S-boxes. Some of the most effective methods known to generate functions that satisfy multiple criteria are based on evolutionary heuristics. In this paper, we improve on these algorithms by employing an adaptive strategy. Additionally, using recent improvements in the understanding of these combinatorial structures, we discover essential properties of the graph formed by affine equivalence classes of Boolean functions, which offers several advantages as a conceptual model for multiobjective seeking evolutionary heuristics. Finally, we propose the first major global cooperative effort to discover new bounds for cryptographic properties of Boolean functions. Show less

The manipulation and analysis of Boolean functions for cryptographic applications typically involves a substantial amount of computational processing, particularly for Boolean functions of a large number of input variables. To date, little consideration has been given to the provision of efficient Boolean function programming techniques in the related cryptographic literature. This paper will examine a range of general optimisation techniques that can be applied to Boolean function programs.… Show more

The manipulation and analysis of Boolean functions for cryptographic applications typically involves a substantial amount of computational processing, particularly for Boolean functions of a large number of input variables. To date, little consideration has been given to the provision of efficient Boolean function programming techniques in the related cryptographic literature. This paper will examine a range of general optimisation techniques that can be applied to Boolean function programs. A structure and code for the optimal implementation of Boolean functions and their associated operations, including the Walsh-Hadamard transform and Algebraic Normal Form transform, will be presented using the C language.
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The LILI-II keystream generator is a LFSR based synchronous stream cipher with a 128 bit key. LILI-II is a specific cipher from the LILI family of keystream generators, and was developed to overcome some of the weaknesses which have been identified in the LILI-128 keystream generator. The design offers large period and linear complexity, is resistant to currently known styles of attack, and is simple to implement in hardware or software.