Evaluating Coppersmith’s Criteria by way of SAT Solving

S-boxes are the non-linear part of DES cryptosystem. Along the years it has became clear that any kind of edit to the structure of DES S-boxes increases the probability of success of breaking the algorithm, which was very carefully designed. The reason why the S-boxes were built in this way was clarified by Coppersmith, years after the publication of the encryption algorithm. The aim of this thesis is to investigate on Coppersmith’s DES S-boxes design criteria and to evaluate them by way of SAT Solving, in order to analyze the performance of SAT-Solvers for different versions of DES algorithm, in which S-boxes respect only a sample of Coppersmith’s design criteria. This aim is achieved thanks to the implementation of a Python tool: DESBoxGen. The main challenge in the design of DESBoxGen is the one of finding a way to efficiently generating S-boxes satisfying certain criteria

Block Ciphers: Analysis, Design and Applications

In this thesis we study cryptanalysis, applications and design of secret key block ciphers. In particular, the important class of Feistel ciphers is studied, which has a number of rounds, where in each round one applies a cryptographically weak function

Communication Efficient Algorithms for Distributed OLAP Query Execution

As a result of the growing amounts of Data in todays Databases, one machine is often not sufficient to store and process these. The proper solution to this problem is to scale the system out on a cluster. However, the distribution of the data throughout the machines of the cluster results in a high percentage of communication time in the overall execution time of a query, especially for complex analytical queries. For this reason, we try to minimize the volume of communicated data to allow faster runtimes when a query cannot be executed on a single node of the cluster without any communication. We analyze techniques from previous work and propose improvements to them backed by a complexity analysis of the communication volume for both, our algorithms and the algorithms from the previous work. For the evaluation of our algorithms we implement them for chosen queries of the TPC-H benchmark and run them on a cluster of up to 128 nodes with a database of up to 30 terabytes of uncompressed data (128 TB if only a small proportion of the database is used). We provide both, scaling experiments and runtime comparisons to previous work and the current TPC-H record holder. The main contributions of this work are: • A technique to find a better partitioning of the tables in a database to allow the execution of joins without communication effort • An algorithm that selects the first k tuples of the result set of a query with a communication effort independent from the size of the database, given certain conditions of the partitioning • An analysis of the communication effort of a delayed join that can’t be evaluated locally on a node, in comparison to the communication effort when executing the join early • The application of our algorithms to solve complex queries of the TPC-H benchmark that can’t be executed without a high amount of communication effort • The implementation of the queries in a prototype and evaluation of our algorithms on a large cluster consisting of 128 nodes for a database with up to 30 terabytes of uncompressed data (or 128 TB if only a small proportion of the database is used

Adaptive Encryption Techniques In Wireless Communication Channels With Tradeoffs Between Communication Reliability And Security

Encryption is a vital process to ensure the confidentiality of the information transmitted over an insecure wireless channel. However, the nature of the wireless channel tends to deteriorate because of noise, interference and fading. Therefore, a symmetrically encrypted transmitted signal will be received with some amount of error. Consequently, due to the strict avalanche criterion (sac), this error propagates during the decryption process, resulting in half the bits (on average) after decryption to be in error. In order to alleviate this amount of error, smart coding techniques and/or new encryption algorithms that take into account the nature of wireless channels are required. The solution for this problem could involve increasing the block and key lengths which might degrade the throughput of the channel. Moreover, these solutions might significantly increase the complexity of the encryption algorithms and hence to increase the cost of its implementation and use. Two main approaches have been folloto solve this problem, the first approach is based on developing an effective coding schemes and mechanisms, in order to minimize and correct the errors introduced by the channel. The second approach is more focused on inventing and implementing new encryption algorithms that encounter less error propagation, by alleviating the sac effect. Most of the research done using these two approaches lacked the comprehensiveness in their designs. Some of these works focused on improving the error performance and/or enhancing the security on the cost of complexity and throughput. In this work, we focus on solving the problem of encryption in wireless channels in a comprehensive way that considers all of the factors in its structure (error performance, security and complexity). New encryption algorithms are proposed, which are modifications to the standardized encryption algorithms and are shown to outperform the use of these algorithms in wireless channels in terms of security and error performance with a slight addition in the complexity. We introduce new modifications that improve the error performance for a certain required security level while achieving the highest possible throughput. We show how our proposed algorithm outperforms the use of other encryption algorithms in terms of the error performance, throughput, complexity, and is secure against all known encryption attacks. In addition, we study the effect of each round and s-box in symmetric encryption algorithms on the overall probability of correct reception at the receiver after encryption and the effect on the security is analyzed as well. Moreover, we perform a complete security, complexity and energy consumption analysis to evaluate the new developed encryption techniques and procedures. We use both analytical computations and computer simulations to evaluate the effectiveness of every modification we introduce in our proposed designs

Теоретико-концептуальный подход к проблеме качества и ценности информации в эргасистеме

The theoretical and conceptual approach to information quality and value problem is considered. The approach includes the choice and determination of types and qualitative forms of information manifestation that are characteristic of the ergatic systems, the efficient distribution in ergatic system of the accepted information measures, the main requirements on measures of quantity and quality of structural and content information, the principal of information value.Рассматривается теоретико-концептуальный подход к проблеме качества и ценности информации в эргасистеме, включающий выбор и определение видов и качественных форм проявления информации, характерных для эргасистем, рациональное распределение в эргасистеме апробированных информационных мер, основные требования к мерам количества и качества структурной и содержательной информации, принцип информационной ценности

On weak rotors, Latin squares, linear algebraic representations, invariant differentials and cryptanalysis of Enigma

Since the 1920s until today it was assumed that rotors in Enigma cipher machines do not have a particular weakness or structure. A curious situation compared to hundreds of papers about S-boxes and weak setup in block ciphers. In this paper we reflect on what is normal and what is not normal for a cipher machine rotor, with a reference point being a truly random permutation. Our research shows that most original wartime Enigma rotors ever made are not at all random permutations and conceal strong differential properties invariant by rotor rotation. We also exhibit linear/algebraic properties pertaining to the ring of integers modulo 26. Some rotors are imitating a certain construction of a perfect quasigroup which however only works when N is odd. Most other rotors are simply trying to approximate the ideal situation. To the best of our knowledge these facts are new and were not studied before 2020