Universal homophonic coding

Redundancy in plaintext is a fertile source of attack in any encryption system. Compression before encryption reduces the redundancy in the plaintext, but this does not make a cipher more secure. The cipher text is still susceptible to known-plaintext and chosen-plaintext attacks. The aim of homophonic coding is to convert a plaintext source into a random sequence by randomly mapping each source symbol into one of a set of homophones. Each homophone is then encoded by a source coder after which it can be encrypted with a cryptographic system. The security of homophonic coding falls into the class of unconditionally secure ciphers. The main advantage of homophonic coding over pure source coding is that it provides security both against known-plaintext and chosen-plaintext attacks, whereas source coding merely protects against a ciphertext-only attack. The aim of this dissertation is to investigate the implementation of an adaptive homophonic coder based on an arithmetic coder. This type of homophonic coding is termed universal, as it is not dependent on the source statistics.Computer ScienceM.Sc. (Computer Science

Heuristic Search Cryptanalysis of the Zodiac 340 Cipher

The Zodiac 340 cipher is one of the most famous unsolved ciphers of all time. It was allegedly written by “the Zodiac”, whose identity remains unknown to date. The Zodiac was a serial killer who killed a number of people in and around the San Francisco Bay area during the 1960s. He is confirmed to have seven victims, two of whom survived [1], although in taunting letters to the news media he claims to have killed 37 people. During this time, an encrypted message known as the Zodiac 408 cipher was mailed to 3 different newspapers in the San Francisco bay area. This was a homophonic cipher and was successfully decoded. Within a few days he sent out another cipher that was 340 characters long [4]. This cipher, which is known as the Zodiac 340 cipher, is unsolved to date. Many cryptologists have tried to crack this cipher but with no success. In this project, we implemented a novel genetic algorithm in an attempt to crack the Zodiac 340 cipher. We have attacked the cipher as a homophonic cipher where each cipher symbol is mapped to only a single English letter, but each English letter can be mapped to multiple cipher symbols. In the genetic algorithm, we implemented two variants of crossover: simple and intelligent. The simple crossover looks for commonly occurring substrings, without looking for actual English words in a putative decrypt. The intelligent crossover counts the number of actual English words that can be found in a putative decrypt when evaluating each solution. We implemented a dictionary lookup for quickly identifying English words for the intelligent crossover. The genetic algorithm using a combination of simple and intelligent crossovers was able to identify many English words in various putative decrypts but no solution was found

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Graduate Course Descriptions, 2006 Winter

Wright State University graduate course descriptions from Winter 2006

Graduate Course Descriptions, 2005 Fall

Wright State University graduate course descriptions from Fall 2005