published_or_final_version / Botany / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 102-109).

Title: Homomorphic encryption and coding theory Author: Veronika Půlpánová Department: Department of algebra Supervisor: RNDr. Michal Hojsík, Ph.D., Department of algebra Abstract: The current mainstream in fully homomorphic encryption is the appro- ach that uses the theory of lattices. The thesis explores alternative approaches to homomorphic encryption. First we present a code-based homomorphic encrypti- on scheme by Armknecht et. al. and study its properties. Then we describe the family of cryptosystems commonly known as Polly Cracker and identify its pro- blematic aspects. The main contribution of this thesis is the design of a new fully homomorphic symmetric encryption scheme based on Polly Cracker. It proposes a new approach to overcoming the complexity of the simple Polly Cracker - based cryptosystems. It uses Gröbner bases to generate zero-dimensional ideals of po- lynomial rings over finite fields whose factor rings are then used as the rings of ciphertexts. Gröbner bases equip these rings with a multiplicative structure that is easily algorithmized, thus providing an environment for a fully homomorphic cryptosystem. Keywords: Fully homomorphic encryption, Polly Cracker, coding theory, zero- dimensional ideals

Title: Applications of Gröbner bases in cryptography Author: Aleš Fuchs Department: Department of Algebra Supervisor: Mgr. Jan Št'ovíček Ph.D., Department of Algebra Abstract: In the present paper we study admissible orders and techniques of multivariate polynomial division in the setting of polynomial rings over finite fields. The Gröbner bases of some ideal play a key role here, as they allow to solve the ideal membership problem thanks to their properties. We also explore features of so called reduced Gröbner bases, which are unique for a particular ideal and in some way also minimal. Further we will discuss the main facts about Gröbner bases also in the setting of free algebras over finite fields, where the variables are non-commuting. Contrary to the first case, Gröbner bases can be infinite here, even for some finitely generated two- sided ideals. In the last chapter we introduce an asymmetric cryptosystem Polly Cracker, based on the ideal membership problem in both commutative and noncommutative theory. We analyze some known cryptanalytic methods applied to these systems and in several cases also precautions dealing with them. Finally we summarize these precautions and introduce a blueprint of Polly Cracker reliable construction. Keywords: noncommutative Gröbner bases, Polly Cracker, security,...

My project tells the origins of the Cracker Kung-Fu system through personal narrative and government documents. The personal combat methods of the system are shown and described. The Tire Iron Form, or set of movements, is shown in its entirety, and each martial application is shown.

Dietary fiber is a component in the structure of plants which is an important aspect of diet and nutrition. The demand of fiber has increased significantly, as consumers recognize its health benefits such as reduction of risk of colon cancer, cholesterol lowering affect, regulating blood glucose levels and low calorie intake. Therefore food manufacturers pay more attention to develop new products containing high fiber content. Of all the categories of food products, bakery products are the most common fiber-enriched products. In this research two different wheat bran fibers (coarse and fine fibers) that are produced by microfluidization method are utilized in one of the highly consumed bakery product &ldquo / cracker&rdquo / . In this thesis study coarse and fine wheat bran fibers were utilized in different amounts with replace to wheat bran (0,15, 25, 35, 45, 55, 65, 75 g). The effects of wheat bran fiber on crackers were determined by rheological measurements of dough samples and it was found that as the amount of wheat bran fiber increases / elasticity increases as well. Textural analysis were conducted for both dough and cracker samples and these analysis demonstrated that wheat bran fiber containing dough had higher hardness values than non/less containing ones. In addition to the above analysis, HPLC analyses were done for ferulic acid determination which is a significant nutritive compound in wheat bran. It was concluded that ferulic acid amount in fiber was much higher than wheat bran. This research demonstrated that more nutritive and much fiber containing crackers could be made by using wheat bran fiber instead of wheat bran.

This Master’s thesis is dealt in the local area network security, cryptographic algorithms, particular attacks on computer networks a practical application these attacks in local area networks. To application particular attacks is used the Cain & Abel program. The detailed manual for this program is created from the results of these attacks. This manual contains the exhibits of usage particular program tools and the attack application exhibits. This manual considers consequences of particular attacks and summarises achieved results during work with tools too. Master thesis closely deals with one of the program tools called RSA SecureID Token Calculator. Authentication via hardware tokens is contained in this Master thesis. Thesis contains the way of authentication using RSA SecureID Token Calculator without physical owning of the hardware token. Cain & Abel program shows and interprets why cashed passwords in operation system are dangerous and it shows methods how attacker can reveal this passwords from the operation system memory. This Master thesis is focused on sniffing credentials and passwords in local area networks and it is focused on cryptographic algorithms cracking for username and passwords revealing.

Cattle ranching has been of major significance to Florida since the 16th century; however, few are aware of the historic, ecologic, economic and cultural influence of this industry. This study investigates the origins and impacts of the traditional customs and practices of Florida’s cattle ranchers, who preserve and reinvent this rich heritage today. Ranchers live closely with the land and their animals and, due to the often-uncertain and cyclical nature of the business, must possess resourcefulness and initiative to prosper. The image of the stoic cowboy has long been associated with the American West, yet before longhorn cattle ever crossed the western plains, Florida frontiers were populated with herds of unique “cracker” cows, descendants of cattle left behind by early Spanish settlers. Like the West, Florida experienced conflicts between ranchers and other land claimants, issues that continue in the 21st century. Modern ranchers contend with developers, environmental concerns, and increasing regulation, yet they persevere in passing on their cultural heritage. Agricultural lifestyles can be emotionally fulfilling, but stewardship of land and animals can be stressful and labor-intensive. Motivation to continue these customs may be enhanced by identification with cowboys of popular American media, enhanced by physical immersion in a similar setting. Optimal agricultural practices have been well researched; however, anthropology provides a useful lens to examine customs and practices of Florida’s cattle ranchers. Anthropologists have long been concerned with the dynamic relationship between human culture and the environment, examining how the physical landscape and ecological niches shape and are shaped by those who inhabit them. As globalized trade markets, technology, and economies expand, influencing agricultural practices and destroying natural habitats, diachronic studies of changing environments, economic and sociocultural influences in geographically bounded locales can be helpful in understanding this process. iv However, a key consideration is the fact that culture is not static, but ever changing, thus the most important aspects of tradition and heritage that we choose to retain and reinvent may provide the most telling insight into any society

We develop a public key cryptosystem whose security is based on the intractability of the ideal membership problem for a noncommutative algebra over a finite field. We show that this system, which is the noncommutative analogue of the Polly Cracker cryptosystem, is more secure than the commutative version. This is due to the fact that there are a number of ideals of noncommutative algebras (over finite fields) that have infinite reduced Groebner bases, and can be used to generate a public key. We present classes of such ideals and prove that they do not have a finite Groebner basis under any admissible order. We also examine various techniques to realize finite Groebner bases, in order to determine whether these ideals can be used effectively in the design of a public key cryptosystem. We then show how some of these classes of ideals, which have infinite reduced Groebner bases, can be used to design a public key cryptosystem. We also study various techniques of encryption. Finally, we study techniques of cryptanalysis that may be used to attack the cryptosystems that we present. We show how poorly constructed public keys can in fact, reveal the private key, and discuss techniques to design public keys that adequately conceal the private key. We also show how linear algebra can be used in ciphertext attacks and present a technique to overcome such attacks. This is different from the commutative version of the Polly Cracker cryptosystem, which is believed to be susceptible to "intelligent" linear algebra attacks. / Ph. D.

This study utilizes William Benoit’s Image Repair Theory to frame the dominant crisis communication strategies that fast food chain Chick-fil-A (CFA) employed before, during and after their CEO mixed his personal opinion on social issues with corporate policy in June 2012. The thematic analysis draws from three distinct data sets that include 3,900 Facebook comments posted by the general public on CFA’s social media page, 32 individual Atlanta Journal-Constitution news articles that address the debate and CFA’s public response to the crisis titled “Who We Are.” This thesis aims to identify both the dominant themes in Facebook posts and the news articles, as well as how these themes are situated within Benoit’s Image Repair Theory. Research shows that CFA representatives utilized eight of Benoit’s 14 strategies to address their CEO’s comments on gay marriage in an attempt to salvage their reputation. The transcendence strategy was used more than any other throughout the crisis. The thematic analysis of Facebook comments showed that religion and loyalty were the most addressed theme within social media users’ posts on the company’s page. Research also shows that a national boycott initiated against CFA by the LGBTQ community did not hurt the company, but may have helped to spur brand recognition and overall sales. Another pertinent question arose during this research; did company representatives purposely forgo sharing their 2011 and 2012 tax documents that prove they had already stopped contributing to supposed anti-gay organizations more than a year before the controversy arose? Was CFA benefiting from the crisis to such an extent that they strategically remained silent and allowed the misconception to take place when they could have ended the crisis and shown proof?