Neural Networks and the Search for a Quadratic Residue Detector

This paper investigates the feasibility of employing artificial neural network techniques for solving fundamental cryptography problems, taking quadratic residue detection as an example. The problem of quadratic residue detection is one which is well known in both number theory and cryptography. While it garners less attention than problems such as factoring or discrete logarithms, it is similar in both difficulty and importance. No polynomial—time algorithm is currently known to the public by which the quadratic residue status of one number modulo another may be determined. This work leverages machine learning algorithms in an attempt to create a detector capable of solving instances of the problem more efficiently. A variety of neural networks, currently at the forefront of machine learning methodologies, were compared to see if any were capable of consistently outperforming random guessing as a mechanism for detection. Surprisingly, neural networks were repeatably able to achieve accuracies well in excess of random guessing on numbers up to 20 bits in length. Unfortunately, this performance was only achieved after a super—polynomial amount of network training, and therefore we do not believe that the system as implemented could scale to cryptographically relevant inputs of 500 to 1000 bits. This nonetheless suggests a new avenue of attack in the search for solutions to the quadratic residues problem, where future work focused on feature set refinement could potentially reveal the components necessary to construct a true closed—form solution

Methods for Generating High-Fidelity Trace Chemical Residue Reflectance Signatures for Active Spectroscopy Classification Applications

Standoff detection and identification of trace chemicals in hyperspectral infrared images is an enabling capability in a variety of applications relevant to defense, law enforcement, and intelligence communities. Performance of these methods is impacted by the spectral signature variability due to the presence of contaminants, surface roughness, nonlinear effects, etc. Though multiple classes of algorithms exist for the detection and classification of these signatures, they are limited by the availability of relevant reference datasets. In this work, we first address the lack of physics-based models that can accurately predict trace chemical spectra. Most available models assume that the chemical takes the form of spherical particles or uniform thin films. A more realistic chemical presentation that could be encountered is that of a non-uniform chemical film that is deposited after evaporation of the solvent which contained the chemical. This research presents an improved signature model for this type of solid film. The proposed model, called sparse transfer matrix (STM), includes a log-normal distribution of film thicknesses and is found to reduce the root-mean-square error between simulated and measured data by about 25% when compared with either the particle or uniform thin film models. When applied to measured data, the sparse transfer matrix model provides a 0.10-0.28 increase in classification accuracy over traditional models. There remain limitations in the STM model which prevent the predicted spectra from being well-matched to the measured data in some cases. To overcome this, we leverage the field of domain adaptation to translate data from the simulated to the measured data domain. This thesis presents the first one-dimensional (1D) conditional generative adversarial network (GAN) to perform spectrum-to-spectrum translation of reflectance signatures. We apply the 1D conditional GAN to a library of simulated spectra and quantify the improvement with the translated library. The method demonstrates an increase in overall classification accuracy to 0.723 from the accuracy of 0.622 achieved using the STM model when tested on real data. However, the performance improvement is biased towards data included in the GAN training set. The next phase of the research focuses on learning models that are more robust to different parameter combinations for which we do not have measured data. This part of the research leverages elements from the field of theory-guided data science. Specifically, we develop a physics-guided neural network (PGNN) for predicting chemical reflectance for a set of parameterized inputs that is more accurate than the state-of-the-art physics-based signature model for chemical residues. After training the PGNN, we use it to generate a library of predicted spectra for training a classifier. We compare the classification accuracy when using this PGNN library versus a library generated by the physics-based model. Using the PGNN, the average classification accuracy increases to 0.813 on real chemical reflectance data, including data from chemicals not included in the PGNN training set. The products of this thesis work include methods for producing realistic trace chemical residue reflectance signatures as well as demonstrations of improved performance in active spectroscopy classification applications. These methods provide great value to a range of scientific communities. The novel STM signature model enables existing spectroscopy sensors and algorithms to perform well on real-world problems where chemical contaminants are non-uniform. The 1D conditional GAN is the first of its kind and can be applied to many other 1D datasets, such as audio and other time-series data. Finally, the application of theory-guided data science to the trace chemical problem not only enhances the quality of results for known targets and backgrounds, but also increases the robustness to new targets

Development of soft computing and applications in agricultural and biological engineering

Soft computing is a set of “inexact” computing techniques, which are able to model and analyze very complex problems. For these complex problems, more conventional methods have not been able to produce cost-effective, analytical, or complete solutions. Soft computing has been extensively studied and applied in the last three decades for scientific research and engineering computing. In agricultural and biological engineering, researchers and engineers have developed methods of fuzzy logic, artificial neural networks, genetic algorithms, decision trees, and support vector machines to study soil and water regimes related to crop growth, analyze the operation of food processing, and support decision-making in precision farming. This paper reviews the development of soft computing techniques. With the concepts and methods, applications of soft computing in the field of agricultural and biological engineering are presented, especially in the soil and water context for crop management and decision support in precision agriculture. The future of development and application of soft computing in agricultural and biological engineering is discussed

Efficiency of two decoders based on hash techniques and syndrome calculation over a Rayleigh channel

The explosive growth of connected devices demands high quality and reliability in data transmission and storage. Error correction codes (ECCs) contribute to this in ways that are not very apparent to the end user, yet indispensable and effective at the most basic level of transmission. This paper presents an investigation of the performance and analysis of two decoders that are based on hash techniques and syndrome calculation over a Rayleigh channel. These decoders under study consist of two main features: a reduced complexity compared to other competitors and good error correction performance over an additive white gaussian noise (AWGN) channel. When applied to decode some linear block codes such as Bose, Ray-Chaudhuri, and Hocquenghem (BCH) and quadratic residue (QR) codes over a Rayleigh channel, the experiment and comparison results of these decoders have shown their efficiency in terms of guaranteed performance measured in bit error rate (BER). For example, the coding gain obtained by syndrome decoding and hash techniques (SDHT) when it is applied to decode BCH (31, 11, 11) equals 34.5 dB, i.e., a reduction rate of 75% compared to the case where the exchange is carried out without coding and decoding process