Search Results (102)

The increase in Internet of Things (IoT) devices has introduced significant security challenges, primarily due to their inherent constraints in computational power, memory, and energy. This study provides a comparative performance analysis of selected modern cryptographic algorithms on a resource-constrained IoT platform, the Nordic Thingy:53. We evaluated a set of ciphers including the NIST lightweight standard ASCON, eSTREAM finalists Salsa20, Rabbit, Sosemanuk, HC-256, and the extended-nonce variant XChaCha20. Using a dual test-bench methodology, we measured energy consumption and performance under two distinct scenarios: a low-data-rate Bluetooth mesh network and a high-throughput bulk data transfer. The results reveal significant performance variations among the algorithms. In high-throughput tests, ciphers like XChaCha20, Salsa20, and ASCON32 demonstrated superior speed, while HC-256 proved impractically slow for large payloads. The Bluetooth mesh experiments quantified the direct relationship between network activity and power draw, underscoring the critical impact of cryptographic choice on battery life. These findings offer an empirical basis for selecting appropriate cryptographic solutions that balance security, energy efficiency, and performance requirements for real-world IoT applications. Full article

In several stream cipher designs, Boolean functions (BFs) play a crucial role as non-linear components, either serving as filtering functions or being used within the combining process. The overall strength of stream ciphers mainly depends on certain cryptographic properties of BFs, including their balancedness, non-linearity, resistance to correlation, and algebraic degrees. In this paper, we present novel findings related to the algebraic degrees of BFs, which play an important role in the design of symmetric cryptographic systems, and propose a novel algorithm to directly deduce the algebraic degree of a Boolean function (BF) from its truth table. We also explore new results concerning balanced Boolean functions, specifically characterizing them by establishing new results regarding their support. Additionally, we propose a new approach for a subclass of affine equivalent Boolean functions and discuss well-known cryptographic properties in a very simple and lucid manner using this newly introduced approach. Moreover, we propose the first algorithm in the literature to construct non-quadratic balanced Boolean functions (NQBBFs) that possess no linear structure where their derivative equals 1. Finally, we discuss the complexity of this algorithm and present a table that shows the time taken by this algorithm, after its implementation in SageMath, for the generation of Boolean functions corresponding to different values of n (i.e., number of variables). Full article

This study surveys some cryptographic algorithms in a detailed manner; it mainly focuses on symmetric key cryptography and asymmetric key cryptography with hash functions following them. Regarding the importance of cryptography for securing communications and data integrity in the digital era, we show—using practical examples with Python 3.10 and Crypto 2 tool—how a few implementations of such encryption techniques work. To clarify this further, Caesar Cipher represents a very simple varying key, and each round of stream ciphers or block ciphers exhibits highly advanced symmetric techniques. Then, we discuss asymmetric cryptography using RSA encryption with public–private key pairs for a secure communication. Furthermore, research has been conducted into the hash functions SHA-1 and SHA-2, which form unique digital fingerprints of the information provided. This approach allows us to highlight all the positive and negative aspects of the above tools and to identify the comparative characteristics of their degree of security. This fact is highly important in determining the applicability of the security tools described above, depending on the conditions of work and threats. Full article

This paper presents a power-aware Reconfigurable Parameterizable Pseudorandom Pattern Generator (RP-PRPG) for a number of applications, including built in self-testing (BIST) and cryptography. Linear Feedback Shift Registers (LFSRs) are broadly utilized in pattern generation due to their efficiency and simplicity. However, the diversity of generated patterns, as well as their power consumption, improves through circuit modifications. This work explores enhancements to LFSR structures to achieve broader range of patterns with reduced power consumption for BIST-based applications. The proposed circuit constructed on the LFSR platform can be programmed to generate patterns with varying degrees of different LFSR configurations. Diverse set of patterns of any circuit arrangement can be created using any characteristic polynomial and by utilizing the reseeding capacity of the circuit. The circuit combines a double-tier linear feedback circuit with zero forcing methods, resulting in more than 70% transition reduction, thus significantly lowering power dissipation. The behaviour of the proposed circuit is assessed for characteristic polynomials with degrees ranging from 4 to 128 using various Linear Feedback Shift Register (LFSR) topologies. For reconfigurable HDL and ASIC synthesis, the power-aware RP-PRPG can be used to generate an efficient set of stream ciphers as well as applications involving the scan-for-test protocol. Full article

With the rapid proliferation of real-time digital communication, particularly in multimedia applications, securing transmitted image data has become a vital concern. While chaotic systems have shown strong potential for cryptographic use, most existing approaches rely on low-dimensional, integer-order architectures, limiting their complexity and resistance to attacks. Advances in fractional calculus and memristive technologies offer new avenues for enhancing security through more complex and tunable dynamics. However, the practical deployment of high-dimensional fractional-order memristive chaotic systems in hardware remains underexplored. This study addresses this gap by presenting a secure image transmission system implemented on a field-programmable gate array (FPGA) using a universal high-dimensional memristive chaotic topology with arbitrary-order dynamics. The design leverages four- and five-dimensional hyperchaotic oscillators, analyzed through bifurcation diagrams and Lyapunov exponents. To enable efficient hardware realization, the chaotic dynamics are approximated using the explicit fractional-order Runge–Kutta (EFORK) method with the Caputo fractional derivative, implemented in VHDL. Deployed on the Xilinx Artix-7 AC701 platform, synchronized master–slave chaotic generators drive a multi-stage stream cipher. This encryption process supports both RGB and grayscale images. Evaluation shows strong cryptographic properties: correlation of $-6.1081\times {10}^{-5}$, entropy of 7.9991, NPCR of 99.9776%, UACI of 33.4154%, and a key space of $2^{1344}$, confirming high security and robustness. Full article

In recent decades, a wide variety of Internet of Things (IoT) devices have been using encrypted communication. Hence, so-called light-weight cryptography has become especially important. The main advantage of stream ciphers is that their complexity, operation requirements, and memory usage are negligible compared to block ciphers. At the same time, these ciphers do not have the avalanche effect typical of block ciphers. The avalanche effect is the most important advantage of a block cipher over a stream cipher. A good block cipher will have an appropriate avalanche effect, whereas stream ciphers have no avalanche effect at all. Without this effect, stream ciphers can easily be broken by plaintext attacks. In this paper, we study a modified stream cipher and attempt to add an avalanche effect to the system. The original stream cipher at issue is a so-called “DH3 cryptosystem” (Dömösi and Horváth cryptosystem 3), which is particularly suitable for a variety of problems, e.g., for simple IoT devices. We are going to use the stream cipher in the Cipher Block Chaining (CBC) mode of operation. The CBC operational mode is very popular among block ciphers. With this technique, a DH3 stream cipher can be raised to the same level of security as a block cipher, while retaining the simplicity of its design. Full article

Authenticated encryption with associated data (AEAD) schemes based on stream ciphers, such as ASCON and MORUS, typically use nonlinear feedback shift registers (NFSRs) and linear feedback shift registers (LFSRs) to generate variable-length key streams. While these methods ensure message confidentiality and authenticity, they present challenges in security analysis, especially when automated evaluation is involved. In this paper, we present MLOL, a novel AEAD algorithm based on the LOL framework. MLOL combines authenticated encryption with optimizations to the LFSR structure to enhance both security and efficiency. The cost evaluation demonstrates that on specialized CPU platforms without SIMD instruction set support, MLOL achieves better performance in authenticated encryption speed compared to LOL-MINI with GHASH. Our security analysis confirms that MLOL provides 256-bit security against current cryptanalytic techniques. Experimental results demonstrate that MLOL not only inherits the excellent performance of LOL but also reduces the time complexity of the authenticated encryption process, providing more reliable security guarantees. It significantly simplifies security evaluation, making it suitable for automated analysis tools, and offers a feasible new approach for AEAD algorithm design. Full article

Stream ciphers are a type of symmetric encryption algorithm, and excel in speed and efficiency compared with block ciphers. They are applied in various applications, particularly in digital communications and real-time transmissions. In this paper, we propose lightweight chaotic keystream generators that utilize original one-dimensional (1D) chaotic maps with a counter to fit the requirement of a stream cipher for secure communications in the Internet of Things (IoT). The proposed chaotic scheme, referred to as expanded chaos, improves the limit of the chaotic range for the original 1D chaos. It can resist brute-force attacks, chosen-ciphertext attacks, guess-and-determine attacks, and other known attacks. We implement the proposed scheme on the IoT platform Raspberry Pi. Under NIST SP800-22 tests, the pass rates for the proposed improved chaotic maps with a counter and the proposed the mutual-coupled chaos are found to be at least about 90% and 92%, respectively. Full article

This paper introduces a class of symmetric ciphering systems with a finite secret key, which provides ideal secrecy, autonomy in key generation and distribution, and robustness against the probabilistic structure of messages (the Ideally Secret Autonomous Robust (ISAR) system). The ISAR system is based on wiretap polar codes constructed over an artificial wiretap channel with a maximum secrecy capacity of 0.5. The system autonomously maintains a minimum level of key equivocation by continuously refreshing secret keys without additional key generation and distribution infrastructure. Moreover, it can transform any stream ciphering system with a finite secret key of known length into an ISAR system without knowing and/or changing its algorithm. Therefore, this class of system strongly supports privacy, a critical requirement for contemporary security systems. The ISAR system’s reliance on wiretap polar coding for strong secrecy ensures resistance to passive known plaintext attacks. Furthermore, resistance to passive attacks on generated refreshing keys follows directly from ideal secrecy and autonomy. The results presented offer an efficient methodology for synthesizing this class of systems with predetermined security margins and a complexity of the order of $n\log n$, where $n$ is the block length of the applied polar code. Full article

The RC4 cryptographic algorithm is the most extensively studied stream cipher of the past two decades. This extensive research has resulted in numerous publications, many of which identify various vulnerabilities. Although these vulnerabilities do not preclude the correct use of the algorithm, they complicate its practical implementation. In this paper, we present a novel weakness in the RC4 cipher. Our findings indicate that, for input keys exhibiting certain patterns, the parity of the values in the output permutation of the KSA can be determined with high probability from the parity of its position in the output permutation. Furthermore, the use of keys with these specific patterns leads to noticeable distortions in several bytes of the RC4 output. Full article

This paper discusses the foundation of security theory for the Quantum stream cipher based on the Holevo–Yuen theory, which allows the use of “optical amplifiers”. This type of cipher is a technology that provides information-theoretic security (ITS) to optical data transmission by randomizing ultrafast optical communication signals with quantum noise. In general, the quantitative security of ITS is evaluated in terms of the unicity distance in Shannon theory. However, the quantum version requires modeling beyond the Shannon model of a random cipher to utilize the characteristics of the physical layer. Therefore, as the first step, one has to develop a generalized unicity distance theory and apply it to the evaluation of security. Although a complete theoretical formulation has not yet been established, this paper explains a primitive structure of a generalization of the Shannon random cipher and shows that the realization of this is the generalized quantum stream cipher. In addition, we present several implementation methods of generalized quantum stream ciphers and their security. Full article

Boolean functions are fundamental building blocks in both discrete mathematics and computer science, with applications spanning from cryptography to coding theory. Bent functions, a subset of Boolean functions with maximal nonlinearity, are particularly valuable in cryptographic applications. This study introduces a novel equivalence relation among all Boolean functions and presents an algorithm to generate bent functions based on this relation. We systematically generated a collection of 10,000 bent functions over eight variables, all originating from the same equivalence class, and analyzed their structural complexity through rank determination. Our findings revealed the presence of at least five distinct affine classes of bent functions within this collection. By employing this construction, we devised an algorithm to generate a filter function capable of combining Boolean functions. This filter function can be dynamically adjusted based on a key, offering potential applications in symmetric cipher design, such as enhancing security or improving efficiency. Full article

The elementary cellular automata (ECAs) under the chaotic rule possess long periodicity and are widely used in pseudo-random number generators. However, their period is limited, related to the rule and the number of cells. Meanwhile, the Boolean functions of some ECAs are linear and vulnerable to linear analysis. Thus, the ECA cannot be directly implemented in the stream cipher. In this paper, a hybrid ECA (HECA) with dynamic mask (HECA-M) is designed. The HECA-M consists of two parts: the driving and mask parts. The driving part based on a HECA is used in generating the keystream, and the mask part based on a chaotic ECA is utilized to determine the iterative rule of the driving part. Subsequently, a stream cipher based on the HECA-M and SHA-512 is proposed. The statistic and secure analyses indicate that the proposed stream cipher possesses good randomness and can resist stream cipher analyses, such as exhaustive search, Berlekamp–Massey synthesis, guess and determine attack, time–memory–data tradeoff attack, etc. Hence, the proposed scheme can meet security requirements. Moreover, the time and space consumption of the proposed stream cipher is qualified. Full article

Optical communications providing huge capacity and low latency remain vulnerable to a range of attacks. In consequence, encryption at the optical layer is needed to ensure secure data transmission. In our previous work, we proposed LightPath SECurity (LPSec), a secure cryptographic solution for optical transmission that leverages stream ciphers and Diffie–Hellman (DH) key exchange for high-speed optical encryption. Still, LPSec faces limitations related to key generation and key distribution. To address these limitations, in this paper, we rely on Quantum Random Number Generators (QRNG) and Quantum Key Distribution (QKD) networks. Specifically, we focus on three meaningful scenarios: In Scenario A, the two optical transponders (Tp) involved in the optical transmission are within the security perimeter of the QKD network. In Scenario B, only one Tp is within the QKD network, so keys are retrieved from a QRNG and distributed using LPSec. Finally, Scenario C extends Scenario B by employing Post-Quantum Cryptography (PQC) by implementing a Key Encapsulation Mechanism (KEM) to secure key exchanges. The scenarios are analyzed based on their security, efficiency, and applicability, demonstrating the potential of quantum-enhanced LPSec to provide secure, low-latency encryption for current optical communications. The experimental assessment, conducted on the Madrid Quantum Infrastructure, validates the feasibility of the proposed solutions. Full article

With the rapid proliferation of the Internet of Things (IoT) in recent years, the number of IoT devices has surged exponentially. These devices collect and transmit vast amounts of data, including sensitive information. Encrypting data is a crucial means to prevent unauthorized access and potential misuse. However, the traditional cryptographic schemes offering robust security demand substantial device resources and are unsuitable for lightweight deployments, particularly in resource-constrained IoT devices. On the other hand, with the automotive industry making strides in autonomous driving, self-driving vehicles are beginning to integrate into people’s daily lives. Ensuring the security of autonomous driving systems, particularly in preventing hacker infiltrations, is a paramount challenge currently facing the industry. An emerging lightweight sequence cipher—aiming to strike a balance between security and resource efficiency—has been proposed in this paper based on S-box substitution and arithmetic addition. The designed security threshold is 2⁸⁰. It has been verified that with a slight performance disadvantage, it can reduce memory usage while ensuring the security threshold. The key stream generated by this structure exhibits excellent pseudo-randomness. Full article