Genetic algorithms in cryptography

Genetic algorithms (GAs) are a class of optimization algorithms. GAs attempt to solve problems through modeling a simplified version of genetic processes. There are many problems for which a GA approach is useful. It is, however, undetermined if cryptanalysis is such a problem. Therefore, this work explores the use of GAs in cryptography. Both traditional cryptanalysis and GA-based methods are implemented in software. The results are then compared using the metrics of elapsed time and percentage of successful decryptions. A determination is made for each cipher under consideration as to the validity of the GA-based approaches found in the literature. In general, these GA-based approaches are typical of the field. Of the genetic algorithm attacks found in the literature, totaling twelve, seven were re-implemented. Of these seven, only three achieved any success. The successful attacks were those on the transposition and permutation ciphers by Matthews [20], Clark [4], and Griindlingh and Van Vuuren [13], respectively. These attacks were further investigated in an attempt to improve or extend their success. Unfortunately, this attempt was unsuccessful, as was the attempt to apply the Clark [4] attack to the monoalphabetic substitution cipher and achieve the same or indeed any level of success. Overall, the standard fitness equation genetic algorithm approach, and the scoreboard variant thereof, are not worth the extra effort involved. Traditional cryptanalysis methods are more successful, and easier to implement. While a traditional method takes more time, a faster unsuccessful attack is worthless. The failure of the genetic algorithm approach indicates that supplementary research into traditional cryptanalysis methods may be more useful and valuable than additional modification of GA-based approaches

Using Genetic Algorithm to Break Knapsack Cipher with Sequence Size 16

With the growth of networked system and applications such as eCommerce, the demand for effective internetsecurity is increasing. Cryptology is the science and study of systems for secret communication. It consists of twocomplementary fields of study: cryptography and cryptanalysis.The genetic algorithm is one of the search methods, whichfinds the optimal solution. It is one of the methods, which is used to decrypt cipher.This work focuses on using GeneticAlgorithms to cryptanalyse knapsack cipher. The knapsack cipher is with a knapsack sequence of size 16 to encrypt twocharacters together. Different values of parameters have been used: Population size, mutation rate, number of generation

Breaking Data Encryption Standard with a Reduced Number of Rounds Using Metaheuristics Differential Cryptanalysis

This article presents the author’s own metaheuristic cryptanalytic attack based on the use of differential cryptanalysis (DC) methods and memetic algorithms (MA) that improve the local search process through simulated annealing (SA). The suggested attack will be verified on a set of ciphertexts generated with the well-known DES (data encryption standard) reduced to six rounds. The aim of the attack is to guess the last encryption subkey, for each of the two characteristics Ω. Knowing the last subkey, it is possible to recreate the complete encryption key and thus decrypt the cryptogram. The suggested approach makes it possible to automatically reject solutions (keys) that represent the worst fitness function, owing to which we are able to significantly reduce the attack search space. The memetic algorithm (MASA) created in such a way will be compared with other metaheuristic techniques suggested in literature, in particular, with the genetic algorithm (NGA) and the classical differential cryptanalysis attack, in terms of consumption of memory and time needed to guess the key. The article also investigated the entropy of MASA and NGA attacks

Multi-operation data encryption mechanism using dynamic data blocking and randomized substitution

Existing cryptosystems deal with static design features such as fixed sized data blocks, static substitution and apply identical set of known encryption operations in each encryption round. Fixed sized blocks associate several issues such as ineffective permutations, padding issues, deterministic brute force strength and known-length of bits which support the cracker in formulating of modern cryptanalysis. Existing static substitution policies are either not optimally fit for dynamic sized data blocks or contain known S-box transformation and fixed lookup tables. Moreover, static substitution does not directly correlate with secret key due to which it has not been shown safer especially for Advanced Encryption Standard (AES) and Data Encryption Standard (DES). Presently, entire cryptosystems encrypt each data block with identical set of known operations in each iteration, thereby lacked to offer dynamic selection of encryption operation. These discussed, static design features are fully known to the cracker, therefore caused the practical cracking of DES and undesirable security pitfalls against AES as witnessed in earlier studies. Various studies have reported the mathematical cryptanalysis of AES up to full of its 14 rounds. Thus, this situation completely demands the proposal of dynamic design features in symmetric cryptosystems. Firstly, as a substitute to fixed sized data blocks, the Dynamic Data Blocking Mechanism (DDBM) has been proposed to provide the facility of dynamic sized data blocks. Secondly, as an alternative of static substitution approach, a Randomized Substitution Mechanism (RSM) has been proposed which can randomly modify session-keys and plaintext blocks. Finally, Multi-operation Data Encryption Mechanism (MoDEM) has been proposed to tackle the issue of static and identical set of known encryption operations on each data block in each round. With MoDEM, the encryption operation can dynamically be selected against the desired data block from the list of multiple operations bundled with several sub-operations. The methods or operations such as exclusive-OR, 8-bit permutation, random substitution, cyclic-shift and logical operations are used. Results show that DDBM can provide dynamic sized data blocks comparatively to existing approaches. Both RSM and MoDEM fulfill dynamicity and randomness properties as tested and validated under recommended statistical analysis with standard tool. The proposed method not only contains randomness and avalanche properties but it also has passed recommended statistical tests within five encryption rounds (significant than existing). Moreover, mathematical testing shows that common security attacks are not applicable on MoDEM and brute force attack is significantly resistive

Cryptographic primitives on reconfigurable platforms.

Tsoi Kuen Hung.Thesis (M.Phil.)--Chinese University of Hong Kong, 2002.Includes bibliographical references (leaves 84-92).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Motivation --- p.1Chapter 1.2 --- Objectives --- p.3Chapter 1.3 --- Contributions --- p.3Chapter 1.4 --- Thesis Organization --- p.4Chapter 2 --- Background and Review --- p.6Chapter 2.1 --- Introduction --- p.6Chapter 2.2 --- Cryptographic Algorithms --- p.6Chapter 2.3 --- Cryptographic Applications --- p.10Chapter 2.4 --- Modern Reconfigurable Platforms --- p.11Chapter 2.5 --- Review of Related Work --- p.14Chapter 2.5.1 --- Montgomery Multiplier --- p.14Chapter 2.5.2 --- IDEA Cipher --- p.16Chapter 2.5.3 --- RC4 Key Search --- p.17Chapter 2.5.4 --- Secure Random Number Generator --- p.18Chapter 2.6 --- Summary --- p.19Chapter 3 --- The IDEA Cipher --- p.20Chapter 3.1 --- Introduction --- p.20Chapter 3.2 --- The IDEA Algorithm --- p.21Chapter 3.2.1 --- Cipher Data Path --- p.21Chapter 3.2.2 --- S-Box: Multiplication Modulo 216 + 1 --- p.23Chapter 3.2.3 --- Key Schedule --- p.24Chapter 3.3 --- FPGA-based IDEA Implementation --- p.24Chapter 3.3.1 --- Multiplication Modulo 216 + 1 --- p.24Chapter 3.3.2 --- Deeply Pipelined IDEA Core --- p.26Chapter 3.3.3 --- Area Saving Modification --- p.28Chapter 3.3.4 --- Key Block in Memory --- p.28Chapter 3.3.5 --- Pipelined Key Block --- p.30Chapter 3.3.6 --- Interface --- p.31Chapter 3.3.7 --- Pipelined Design in CBC Mode --- p.31Chapter 3.4 --- Summary --- p.32Chapter 4 --- Variable Radix Montgomery Multiplier --- p.33Chapter 4.1 --- Introduction --- p.33Chapter 4.2 --- RSA Algorithm --- p.34Chapter 4.3 --- Montgomery Algorithm - Ax B mod N --- p.35Chapter 4.4 --- Systolic Array Structure --- p.36Chapter 4.5 --- Radix-2k Core --- p.37Chapter 4.5.1 --- The Original Kornerup Method (Bit-Serial) --- p.37Chapter 4.5.2 --- The Radix-2k Method --- p.38Chapter 4.5.3 --- Time-Space Relationship of Systolic Cells --- p.38Chapter 4.5.4 --- Design Correctness --- p.40Chapter 4.6 --- Implementation Details --- p.40Chapter 4.7 --- Summary --- p.41Chapter 5 --- Parallel RC4 Engine --- p.42Chapter 5.1 --- Introduction --- p.42Chapter 5.2 --- Algorithms --- p.44Chapter 5.2.1 --- RC4 --- p.44Chapter 5.2.2 --- Key Search --- p.46Chapter 5.3 --- System Architecture --- p.47Chapter 5.3.1 --- RC4 Cell Design --- p.47Chapter 5.3.2 --- Key Search --- p.49Chapter 5.3.3 --- Interface --- p.50Chapter 5.4 --- Implementation --- p.50Chapter 5.4.1 --- RC4 cell --- p.51Chapter 5.4.2 --- Floorplan --- p.53Chapter 5.5 --- Summary --- p.53Chapter 6 --- Blum Blum Shub Random Number Generator --- p.55Chapter 6.1 --- Introduction --- p.55Chapter 6.2 --- RRNG Algorithm . . --- p.56Chapter 6.3 --- PRNG Algorithm --- p.58Chapter 6.4 --- Architectural Overview --- p.59Chapter 6.5 --- Implementation --- p.59Chapter 6.5.1 --- Hardware RRNG --- p.60Chapter 6.5.2 --- BBS PRNG --- p.61Chapter 6.5.3 --- Interface --- p.66Chapter 6.6 --- Summary --- p.66Chapter 7 --- Experimental Results --- p.68Chapter 7.1 --- Design Platform --- p.68Chapter 7.2 --- IDEA Cipher --- p.69Chapter 7.2.1 --- Size of IDEA Cipher --- p.70Chapter 7.2.2 --- Performance of IDEA Cipher --- p.70Chapter 7.3 --- Variable Radix Systolic Array --- p.71Chapter 7.4 --- Parallel RC4 Engine --- p.75Chapter 7.5 --- BBS Random Number Generator --- p.76Chapter 7.5.1 --- Size --- p.76Chapter 7.5.2 --- Speed --- p.76Chapter 7.5.3 --- External Clock --- p.77Chapter 7.5.4 --- Random Performance --- p.78Chapter 7.6 --- Summary --- p.78Chapter 8 --- Conclusion --- p.81Chapter 8.1 --- Future Development --- p.83Bibliography --- p.8

Algorytmy metaheurystyczne w kryptoanalizie szyfrów strumieniowych

Metaheuristic algorithms are general algorithms allowing to solve various types of computational problems, usually optimization ones. In the dissertation, new versions of selected metaheuristic algorithms were developed: Tabu Search and Ant Colony Optimization algorithms. They have been adapted to solve the problem of cryptanalysis of stream ciphers, which are an important element of data protection processed and stored in information systems. Attempts to hide information from unauthorized persons have a long history. As early as the 5th century BC there was a simple Atbash substitution cipher among the Hebrew scholars. Although a lot has changed since then, and the art of encrypting information has undergone a significant transformation, the issue of confidentiality of communication is still important. Encryption is used wherever protection of transmitted or stored data, especially in information systems, is of key importance. Encryption is used when talking on the phone or logging in via the Internet to a bank account. It is also of great importance in the military. Encryption is an issue with a long history, still important and topical. The proposed Tabu Search and Ant Colony Optimization algorithms adapted to cryptanalysis were tested using three stream ciphers: RC4, VMPC and RC4+. This enabled the development of an attack independent of the design of the cipher itself, assuming that the internal state of the cipher can be represented as a permutation of numbers from a given range. For all proposed metaheuristic algorithms, four types of fitness functions have been tested, three of which are original ones. The original fitness functions enabled achieving better results for all three analysed metaheuristic algorithms compared to a function known from the literature. Each of the proposed algorithms were tested in terms of the impact of parameters values on the results they achieved. Also the results achieved by all three metaheuristic algorithms were compared to one another. The results obtained during cryptanalysis of smaller and full versions of the analysed ciphers with the use of Tabu Search were compared with the results obtained by other metaheuristic algorithms, showing that Tabu Search leads to better results than other metaheuristics. The results obtained using the Tabu Search algorithm were also compared to attacks known from the literature on selected stream ciphers. The results of the experiments indicate that for the VMPC and RC4+ ciphers, the proposed cryptanalysis algorithm using Tabu Search may be better than the cryptanalysis algorithms known so far. The results achieved by other metaheuristic algorithms considered were not as good as for Tabu Search, although it cannot be ruled out that further enhancement of these algorithms could improve the results