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Despite having many similar characteristics with cryptography, existing chaotic systems have many security issues that negatively affect the chaos-based cryptographic algorithms that utilize them. This paper proposes a new chaotification method that enhances the chaotic complexity of existing chaotic maps to surmount these issues. The proposed method uses a cosine function alongside a chaotic map in a cascade system. To depict its advantages, we apply it to enhance logistic and Henon maps before analyzing their chaotic properties. Results and comparisons indicate that the new chaotic maps have a wider chaotic range, elevated sensitivity, complex characteristics, high nonlinearity, and an extended cycle length as compared to the original (seed) maps as well as other chaotic maps. We then utilize the modified maps (and their corresponding seed maps) to design simple pseudorandom number generators to study their feasibility when used in cryptographic algorithms. We perform comparisons between the generators derived from both the original and seed maps. Results show that generators based on the new maps outperform their seed counterparts in nearly every aspect. This finding demonstrates the capability of the proposed method in improving the performance of chaos-based cryptographic algorithms.

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The success of AES encryption standard created challenges for the cryptographers to construct strong substitution-boxes using different underlying approaches. It is because they are solely responsible to decide the robustness of cryptosystem against linear and differential cryptanalyses. With an aim to fulfill the mentioned requirement of robustness, a novel group theoretic and graphical method is proposed to construct S-box with optimal features. Firstly, a strong S-box is generated with the help of orbits of coset graphs and the action of proposed powerful permutation of symmetric group S 256 . In addition, a specific group is designed the action of whose pairs of permutations has the ability to generate as many as 462422016 strong S-boxes. Few of such proposed S-boxes are reported and assessed against standard performance parameters to validate the effectiveness of proposed findings. The features of proposed S-boxes are compared with most of the recent S-boxes to validate the superior performance. Moreover, they are also applied for image encryption to demonstrate their suitability for multimedia security applications.

Blockchain networks are based on cryptographic notions that include asymmetric-key encryption, hash functions and consensus protocols. Despite their popularity, mainstream protocols, such as Proof of Work or Proof of Stake still have drawbacks. Efforts to enhance these protocols led to the birth of alternative consensus protocols, catering to specific areas, such as medicine or transportation. These protocols remain relatively unknown despite having unique merits worth investigating. Although past reviews have been published on popular blockchain consensus protocols, they do not include most of these lesser-known protocols. Highlighting these alternative consensus protocols contributes toward the advancement of the state of the art, as they have design features that may be useful to academics, blockchain practitioners and researchers. In this paper, we bridge this gap by providing an overview of alternative consensus protocols proposed within the past 3 years. We evaluate their overall performance based on metrics such as throughput, scalability, security, energy consumption, and finality. In our review, we examine the trade-offs that these consensus protocols have made in their attempts to optimize scalability and performance. To the best of our knowledge, this is the first paper that focuses on these alternative protocols, highlighting their unique features that can be used to develop future consensus protocols.

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