A graphical simulator for the cryptanalysis of block ciphers

We have designed and implemented a graphical simulator for the use of students in the Master of Applied Science (information security) program at RMIT University in Melbourne, Australia. During this process, a lot of practical experience was gained which aids future designers who address similar problems, especially if the design aims include the realistic simulation, in a reasonable time, of a process, cryptanalysis - which often takes many days or weeks of computation by powerful computers

PICO : An Ultra Lightweight and Low Power Encryption Design for Ubiquitous Computing

An ultra-lightweight, a very compact block cipher ‘PICO’ is proposed. PICO is a substitution and permutation based network, which operates on a 64 bit plain text and supports a key length of 128 bits. It has a compact structure and requires 1877 GEs. Its innovative design helps to generate a large number of active S - boxes in fewer rounds which can thwart the linear and differential attacks on the cipher. PICO shows good performance on both the hardware and the software platforms. PICO consumes only 2504 bytes of Flash memory which is less than the ultra-lightweight cipher PRESENT. PICO has a very strong substitution layer (S-box) which not only makes the design robust but also introduces a great avalanche effect. PICO has a strong and compact key scheduling which is motivated by the latest cipher SPECK designed by NSA. PICO consumes 28 mW of dynamic power which is less than the PRESENT cipher (38 mW). The security analysis of PICO and its performance as an ultra-lightweight cipher are presented.

New Methodology of Block Cipher Analysis Using Chaos Game

Block cipher analysis  covers randomness analysis and cryptanalysis. This paper proposes a new method potentially used for randomness analysis and cryptanalysis. The method uses true random sequence  concept as a reference for measuring randomness level of a random sequence. By using this concept, this paper  defines  bias  which represents  violation  of  a  random  sequence  from  true random sequence. In this paper, block cipher   is treated as a mapping function of a discrete time dynamical system. The dynamical system framework is used to make  the  application  of  various  analysis  techniques  developed  in  dynamical system  field  becomes  possible.  There  are three  main parts of  the methodology presented  in  this  paper:  the  dynamical  system  framework  for  block  cipher analysis, a  new chaos game  scheme and an extended measure  concept related to chaos game and fractal analysis. This paper also presents the general procedures of the proposed method, which includes: symbolic dynamic analysis of discr ete dynamical system whose block cipher as its mapping function, random sequence construction,  the  random  sequence  usage  as  input  of  a  chaos  game  scheme, output  measurement  of  chaos  game  scheme  using  extended  measure  concept, analysis  the  result  of  the  measurement.  The  analysis  process  and  of  a  specific real or sample block cipher and the analysis result are beyond the scope of this paper

Differential cryptanalysis of substitution permutation networks and Rijndael-like ciphers

A block cipher, in general, consist of several repetitions of a round transformation. A round transformation is a weak block cipher which consists of a nonlinear substitution transformation, a linear diffusion transformation and a key mixing. Differential cryptanalysis is a well known chosen plaintext attack on block ciphers. In this project, differential cryptanalysis is performed on two kinds of block ciphers: Substitution Permutation Networks(SPN) and Rijndael-like Ciphers. In order to strengthen a block cipher against differential attack, care should be taken in the design of both substitution and diffusion components and in the choice of number of rounds. In this context, most of the researches has been focused on the design of substitution component. In this project, differential cryptanalysis is carried out on several SPNs to find the role of permutation. Differential analysis on Rijndael-like ciphers is done to find the strength of the cipher as a whole. Tools are developed to configure and to perform differential analysis on these ciphers. In the context of SPN, the importance of permutation, the effect of bad permutation, no permutation and sequentially chosen plaintext pairs are discussed. The diffusion strength of SPN and Rijndael-like ciphers are discussed and compared

Full-Round Differential Attack on DoT Block Cipher

The lightweight encryption design DoT was published by Patil et al in 2019. It is based on SPN (substitution permutation network) structure. Its block and key size are 64-bit and 128-bit respectively. In this paper, we analyse the security of DoT against differential attack and present a series of differential distinguishers for full-round DOT. Our analysis proves that DoT we can be distinguished from a random permutation with probability equal to 2^62. Diffusion layer of DoT is a combination of byte shuffling, 8-P permutation, 32-bit word shuffling and circular shift operations. We analyse the security of DoT with and without 8-P permutation in its diffusion layer. Our results indicate that DoT provides better resistance to differential attack without using the 8-P permutation

Differential Cryptanalysis of a Lightweight Block Cipher LELBC

In this study, we investigate the newly developed low energy lightweight block cipher (LELBC), specifically designed for resource-constrained Internet of Things (IoT) devices in smart agriculture. The designers conducted a preliminary differential cryptanalysis of LELBC through mixed-integer linear programming (MILP). This paper further delves into LELBC’s differential characteristics in both single and related-key frameworks using MILP, identifying a nine-round differential characteristic with a probability of $2^{-60}$ in a single-key framework and a 12-round differential characteristic with a probability of $2^{-60}$ in a related-key framework

MILP-aided Cryptanalysis of Round Reduced ChaCha

The inclusion of ChaCha20 and Poly1305 into the list of supported ciphers in TLS 1.3 necessitates a security evaluation of those ciphers with all the state-of-the-art tools and innovative cryptanalysis methodologies. Mixed Integer Linear Programming (MILP) has been successfully applied to find more accurate characteristics of several ciphers such as SIMON and SPECK. In our research, we use MILP-aided cryptanalysis to search for differential characteristics, linear approximations and integral properties of ChaCha. We are able to find differential trails up to 2 rounds and linear trails up to 1 round. However, no integral distinguisher has been found, even for 1 round

An enhanced Blowfish Algorithm based on cylindrical coordinate system and dynamic permutation box

The Blowfish Algorithm (BA) is a symmetric block cipher that uses Feistel network to iterate simple encryption and decryption functions. BA key varies from 32 to 448 bits to ensure a high level of security. However, the substitution box (S-Box) in BA occupies a high percentage of memory and has problems in security, specifically in randomness of output with text and image files that have large strings of identical bytes. Thus, the objective of this research is to enhance the BA to overcome these problems. The research involved three phases, algorithm design, implementation, and evaluation. In the design phase, a dynamic 3D S-Box, a dynamic permutation box (P-Box), and a Feistal Function (F-Function) were improved. The improvement involved integrating Cylindrical Coordinate System (CCS) and dynamic P-Box. The enhanced BA is known as Ramlan Ashwak Faudziah (RAF) algorithm. The implementation phase involved performing key expansion, data encryption, and data decryption. The evaluation phase involved measuring the algorithm in terms of memory and security. In terms of memory, the results showed that the RAF occupied 256 bytes, which is less than the BA (4096 bytes). In terms of randomness of text and image files that have large strings of identical bytes, the average rate of randomness for 188 statistical tests obtained values of more than 96%. This means that the RAF has high randomness indicating that it is more secured. Thus, the results showed that the RAF algorithm that integrates the CCS and dynamic P-Box serves as an effective approach that can consume less memory and strengthen security