07021 Abstracts Collection -- Symmetric Cryptography

From .. to .., the Dagstuhl Seminar 07021 ``Symmetric Cryptography\u27\u27 automatically was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

A Formalization of Polytime Functions

We present a deep embedding of Bellantoni and Cook's syntactic characterization of polytime functions. We prove formally that it is correct and complete with respect to the original characterization by Cobham that required a bound to be proved manually. Compared to the paper proof by Bellantoni and Cook, we have been careful in making our proof fully contructive so that we obtain more precise bounding polynomials and more efficient translations between the two characterizations. Another difference is that we consider functions on bitstrings instead of functions on positive integers. This latter change is motivated by the application of our formalization in the context of formal security proofs in cryptography. Based on our core formalization, we have started developing a library of polytime functions that can be reused to build more complex ones.Comment: 13 page

Collision Attack on 5 Rounds of Grøstl

In this article, we describe a novel collision attack for up to 5 rounds of the Grøstl hash function. This significantly improves upon the best previously published results on 3 rounds. By using a new type of differential trail spanning over more than one message block we are able to construct collisions for Grøstl on 4 and 5 rounds with complexity of $2^{67}$ and $2^{120}$, respectively. Both attacks need $2^{64}$ memory. Due to the generic nature of our attack we can even construct meaningful collisions in the chosen-prefix setting with the same attack complexity

MOIM: a novel design of cryptographic hash function

A hash function usually has two main components: a compression function or permutation function and mode of operation. In this paper, we propose a new concrete novel design of a permutation based hash functions called MOIM. MOIM is based on concatenating two parallel fast wide pipe constructions as a mode of operation designed by Nandi and Paul, and presented at Indocrypt 2010 where the size of the internal state is significantly larger than the size of the output. And the permutations functions used in MOIM are inspired from the SHA-3 finalist Grøstl hash function which is originally inspired from Rijndael design (AES). As a consequence there is a very strong confusion and diffusion in MOIM. Also, we show that MOIM resists all the generic attacks and Joux attack in two defense security levels

The Future of Blockchain

Blockchain is the leading technology for cryptocurrencies, NFT’s and other online marketplace transactions that go through it because of it’s secure technology and how they distribute their data with Smart Contracts. This report shows how we can use Blockchain for other uses in our world and how it could advance us in the cybersecurity aspects. Showing also why we should use blockchain with basic cybersecurity concerns as in: Malware Detection, Voter Fraud, and Medical Record Security

Modelos de compressão e ferramentas para dados ómicos

The ever-increasing growth of the development of high-throughput sequencing technologies and as a consequence, generation of a huge volume of data, has revolutionized biological research and discovery. Motivated by that, we investigate in this thesis the methods which are capable of providing an efficient representation of omics data in compressed or encrypted manner, and then, we employ them to analyze omics data. First and foremost, we describe a number of measures for the purpose of quantifying information in and between omics sequences. Then, we present finite-context models (FCMs), substitution-tolerant Markov models (STMMs) and a combination of the two, which are specialized in modeling biological data, in order for data compression and analysis. To ease the storage of the aforementioned data deluge, we design two lossless data compressors for genomic and one for proteomic data. The methods work on the basis of (a) a combination of FCMs and STMMs or (b) the mentioned combination along with repeat models and a competitive prediction model. Tested on various synthetic and real data showed their outperformance over the previously proposed methods in terms of compression ratio. Privacy of genomic data is a topic that has been recently focused by developments in the field of personalized medicine. We propose a tool that is able to represent genomic data in a securely encrypted fashion, and at the same time, is able to compact FASTA and FASTQ sequences by a factor of three. It employs AES encryption accompanied by a shuffling mechanism for improving the data security. The results show it is faster than general-purpose and special-purpose algorithms. Compression techniques can be employed for analysis of omics data. Having this in mind, we investigate the identification of unique regions in a species with respect to close species, that can give us an insight into evolutionary traits. For this purpose, we design two alignment-free tools that can accurately find and visualize distinct regions among two collections of DNA or protein sequences. Tested on modern humans with respect to Neanderthals, we found a number of absent regions in Neanderthals that may express new functionalities associated with evolution of modern humans. Finally, we investigate the identification of genomic rearrangements, that have important roles in genetic disorders and cancer, by employing a compression technique. For this purpose, we design a tool that is able to accurately localize and visualize small- and large-scale rearrangements between two genomic sequences. The results of applying the proposed tool on several synthetic and real data conformed to the results partially reported by wet laboratory approaches, e.g., FISH analysis.O crescente crescimento do desenvolvimento de tecnologias de sequenciamento de alto rendimento e, como consequência, a geração de um enorme volume de dados, revolucionou a pesquisa e descoberta biológica. Motivados por isso, nesta tese investigamos os métodos que fornecem uma representação eficiente de dados ómicros de maneira compactada ou criptografada e, posteriormente, os usamos para análise. Em primeiro lugar, descrevemos uma série de medidas com o objetivo de quantificar informação em e entre sequencias ómicas. Em seguida, apresentamos modelos de contexto finito (FCMs), modelos de Markov tolerantes a substituição (STMMs) e uma combinação dos dois, especializados na modelagem de dados biológicos, para compactação e análise de dados. Para facilitar o armazenamento do dilúvio de dados acima mencionado, desenvolvemos dois compressores de dados sem perda para dados genómicos e um para dados proteómicos. Os métodos funcionam com base em (a) uma combinação de FCMs e STMMs ou (b) na combinação mencionada, juntamente com modelos de repetição e um modelo de previsão competitiva. Testados em vários dados sintéticos e reais mostraram a sua eficiência sobre os métodos do estado-de-arte em termos de taxa de compressão. A privacidade dos dados genómicos é um tópico recentemente focado nos desenvolvimentos do campo da medicina personalizada. Propomos uma ferramenta capaz de representar dados genómicos de maneira criptografada com segurança e, ao mesmo tempo, compactando as sequencias FASTA e FASTQ para um fator de três. Emprega criptografia AES acompanhada de um mecanismo de embaralhamento para melhorar a segurança dos dados. Os resultados mostram que ´e mais rápido que os algoritmos de uso geral e específico. As técnicas de compressão podem ser exploradas para análise de dados ómicos. Tendo isso em mente, investigamos a identificação de regiões únicas em uma espécie em relação a espécies próximas, que nos podem dar uma visão das características evolutivas. Para esse fim, desenvolvemos duas ferramentas livres de alinhamento que podem encontrar e visualizar com precisão regiões distintas entre duas coleções de sequências de DNA ou proteínas. Testados em humanos modernos em relação a neandertais, encontrámos várias regiões ausentes nos neandertais que podem expressar novas funcionalidades associadas à evolução dos humanos modernos. Por último, investigamos a identificação de rearranjos genómicos, que têm papéis importantes em desordens genéticas e cancro, empregando uma técnica de compressão. Para esse fim, desenvolvemos uma ferramenta capaz de localizar e visualizar com precisão os rearranjos em pequena e grande escala entre duas sequências genómicas. Os resultados da aplicação da ferramenta proposta, em vários dados sintéticos e reais, estão em conformidade com os resultados parcialmente relatados por abordagens laboratoriais, por exemplo, análise FISH.Programa Doutoral em Engenharia Informátic