The rapid proliferation of smart IoT devices has heightened the need for secure and efficient mechanisms to ensure the dependability of high-resolution image transmission while preserving computational performance. Current encryption methods often struggle to achieve a balance between robust security and resource efficiency, particularly in resource-constrained IoT environments such as smart cameras, mobile devices, and home automation systems. This paper introduces a novel lightweight image encryption algorithm designed to meet the stringent performance, security, and dependability requirements of IoT systems. The proposed algorithm incorporates a dynamic key expansion mechanism, a three-dimensional (3D) substitution box (S-box) structure, and a tightly integrated permutation process to enhance security and scalability. By dynamically adapting the key generation and encryption processes to image size, the scheme efficiently operates within a single encryption round while maintaining strong diffusion and confusion properties. The integrated permutation and substitution phases are optimized to enhance resilience against cryptographic attacks, such as differential and statistical attacks. Experimental evaluations on IoT devices validate the proposed algorithm's dependability and security, as demonstrated through rigorous correlation tests, entropy analyses, and sensitivity assessments. Comparative studies further establish the algorithm's superior performance in securing multimedia content while adhering to the real-time processing constraints of IoT systems. This work contributes a dependable and secure encryption framework for modern IoT applications, addressing the critical need for privacy and data integrity in increasingly connected environments.

In this paper, we investigate the security of lightweight block ciphers, focusing on those that utilize the ADD -Rotate-XOR (ARX) and AND -Rotate-XOR ( AND -RX) design paradigms. More specifically, we examine their resilience against boomerang-style attacks. First, we propose an automated search strategy that leverages the boomerang connectivity table ( BCT ) for AND operations ( ∧ B C T ) to conduct a complete search for boomerang and rectangle distinguishers for AND -RX ciphers. The proposed search strategy automatically considers all possible ∧ B C T switches in the middle of the boomerang to optimize distinguishing probability. The correctness of the search strategy was verified experimentally. We were able to find the best boomerang and rectangle distinguishers to date in the single-key model for lightweight block ciphers KATAN 32/48/64 and SIMON 32/48. Next, we investigated BCT properties of ARX ciphers and discovered that a truncated boomerang switch could be formulated for the lightweight ARX cipher, CHAM . We were able to find the best single-key and related-key rectangle distinguishers to date for CHAM . Our findings provide more accurate security margins of these lightweight ciphers against boomerang-style attacks.

This paper investigates the security of a lightweight block cipher SAND that has an AND-RX construction. We evaluate its security against boomerang (and rectangle) attacks. First, we analyse SAND ’s boomerang switching properties from the perspective of the AND operation and when SAND ’s nonlinear operations are represented by synthetic S-boxes. We then develop an automated search for boomerang trails that uses the boomerang connectivity table. From the initial boomerang trail, we construct a rectangle distinguisher by enumerating other boomerang trails with the same input and output differences. We found 13-round and 17-round rectangle distinguishers for SAND -64 and SAND -128 with distinguishing probabilities 2 − 43 . 23 and 2 − 95 . 54 respectively. These rectangle distinguishers were used in key recovery attacks on 15 and 19 rounds of SAND -64 and SAND -128 with (time/data/memory) complexities of ( 2 63 . 09 , 2 56 , 2 59 ) and ( 2 123 . 75 , 2 114 , 2 122 ) respectively. In these attacks, we leverage the fact that input differences propagate deterministically over SAND ’s first round. To the best of our knowledge, these are the first boomerang attacks on SAND .

Abstract In recent years, there has been a surge in new chaos-based cryptographic algorithms, many of which claim to have unusually large keyspaces. Although cryptographic primitives such as symmetric-key ciphers should have a secret keyspace large enough to resist brute force attacks, simply increasing the size of a secret key may not lead to improved security margins. An n -bit key may not necessarily have a keyspace of $$2^n-1$$ 2 n - 1 due to the key scheduling algorithm or how the key is used. In this paper, we cryptanalyse several chaos-based algorithms from the perspective of their key schedules. Our numerical analysis is based on the known-plaintext attack model, Kerckhoff’s principle and considers the number representations used for real number computation. Our analysis reveals that the actual security margins for these ciphers are significantly lower, some by a factor of over $$2^{100}$$ 2 100 than what was claimed. We then provide accurate keyspace estimates for these ciphers. Finally, we highlight alternative solutions for how secret keys can be used in the context of chaos-based cryptography and propose a simple key schedule as a proof of concept. Despite its simplicity, the proposed key schedule not only ensures that the keyspace matches the key length but also passes both the NIST and ENT statistical test suites, making it a viable option for generating secure cryptographic keys. Our work contributes towards addressing one of the fundamental problems in chaos-based cryptography that limits its real-world impact and reputation within the cryptographic community.

Blockchain is a distributed ledger in which participating users with varying levels of trust agree on the ledger’s content using a consensus mechanism called consensus protocols. There has been a rising interest in the design of consensus protocols since they play a central role in blockchain architecture. However, many recently proposed consensus protocols lack experimental verification which hampers the possible deployment of these protocols in real-world blockchain networks. In this article, we propose a simple tool called simplified consensus protocol simulator (SIM-P) that can accurately simulate the behavior of these consensus protocols with ease. It is an agent-based stochastic simulator that relies on the sequential Monte Carlo method to model how block publishers are selected. The likelihood of each node (represented as agents) being selected as a block publisher is represented by independent trials in a binomial experiment. We provide a base SIM-P model that simulates Proof of Work (PoW) for benchmarking purposes. The PoW model also serves as the basic structure of the simulator that can be adapted to other protocols. We showcase the flexibility of SIM-P by proposing two additional simulation models for Proof of Reputation-X and Proof of Contribution, both of which lack experimental verification in their original design specifications. We show how the simulator can be used to produce vital metrics, such as throughput, resistance against the 51% attack, and energy consumption. We verify the accuracy of SIM-P by comparing PoW’s simulated results with theoretical estimates and historical Bitcoin data.

In recent years, there has been a rising interest in authenticated encryption with associated data (AEAD) which combines encryption and authentication into a unified scheme. AEAD schemes provide authentication for a message that is divided into two parts: associated data which is not encrypted and the plaintext which is encrypted. However, there is a lack of chaos-based AEAD schemes in recent literature. This paper introduces a new 128-bit chaos-based AEAD scheme based on the single-key Even-Mansour and Type-II generalized Feistel structure. The proposed scheme provides both privacy and authentication in a single-pass using only one 128-bit secret key. The chaotic tent map is used to generate whitening keys for the Even-Mansour construction, round keys, and random s-boxes for the Feistel round function. In addition, the proposed AEAD scheme can be implemented with true random number generators to map a message to multiple possible ciphertexts in a nondeterministic manner. Security and statistical evaluation indicate that the proposed scheme is highly secure for both the ciphertext and the authentication tag. Furthermore, it has multiple advantages over AES-GCM which is the current standard for authenticated encryption.

In today's world of the internet, billions of computer systems are connected to one another in a global network. The internet provides an unsecured channel in which hundreds of terabytes of data is being transmitted daily. Computer and software systems rely on encryption algorithms such as block ciphers to ensure that sensitive data remains confidential and secure. However, adversaries can leverage the statistical behavior of underlying ciphers to recover encryption keys. Accurate evaluation of the security margins of these encryption algorithms remains to be a big challenge. In this paper, we tackle this issue by introducing several searching strategies based on differential cryptanalysis. By clustering differential paths, the searching algorithm derives more accurate distinguishers as compared to examining individual paths, which in turn provides a more accurate estimation of cipher security margins. We verify the effectiveness of this technique on ciphers with the generalized Feistel and SPN structures, whereby the best distinguishers for each of the investigated ciphers were obtained by discovering clusters with thousands of paths. With the KATAN block cipher family as a test case, we also show how to apply the searching algorithm alongside other cryptanalysis techniques such as the boomerang attack and related-key model to obtain the best cryptanalytic results. This also depicts the flexibility of the proposed searching scheme, which can be tailored to improve upon other differential attack variants. In short, the proposed searching strategy realizes an automated security evaluation tool with higher accuracy compared to previous techniques. In addition, it is applicable to a wide range of encryption schemes which makes it a flexible tool for both academic research and industrial purposes.

The success probability of differential and linear cryptanalysis against block ciphers heavily depend on finding differential or linear paths with high statistical bias compared with uniform random distribution. For large number of rounds, it is not a trivial task to find such differential or linear paths. Matsui first investigated this problem and proposed a solution based on a branch and bound algorithm in 1994. Since then, the research on finding good concrete differential or linear path did not receive much attention. In this paper, we revisit the differential attack against several S-Box based block ciphers by carefully studying the differential characteristics. Inspired by Matsui's algorithm, we provide an improved solution with the aid of several searching strategies, which enable us to find by far the best differential characteristics for the two investigated ciphers (LBlock, TWINE) efficiently. Furthermore, we provide another way to evaluate the security of ciphers against differential attack by comparing the strength of the ciphers from differential characteristic's point of view, and we also investigate the accuracy when using the active S-Box to evaluate the security margin against differential attack, which is the common method adapted when new ciphers are designed.