Most recent issue published online in the International Journal of Critical Computer-Based Systems.

1. Enhancing the data security of cloud computing critical systems using layered encryption technique
   In the fast-growing sector of cloud computing, users can employ system resources as needed for data storage and computation. Protecting confidential data is the biggest cloud computing challenge. Security challenges in cloud computing are categorised as network, data, software, infrastructure, identity, and access management. Data concerns typically arise with cloud computing: data loss, dependability, availability, breaches, backup, and ownership. Cloud service companies worry about security and privacy when hosting services. Cloud storage data security can be improved in many ways. Cloud storage encrypts data for maximum protection. Layered encryption improves cloud data security. Scrambling and binary logical operation are used in the two-layered encryption method. Data is separated into square matrix shares on the first layer. This layer swaps the square matrix using scrambling. The second layer turns the scrambled matrix to binary, and the XoR logical operation encrypts it. The AWS cloud stores encrypted data. The algorithms provided great security, reduced cipher text size, and shortened encryption and decryption time compared to previous encryption methods.
2. Controlling dynamic crowdsourcing processes using multi-layered algebraic Petri nets
   Crowdsourcing is an emergent model for decentralised and collaborative problem solving. Inventive tasks crowdsourcing processes are in most cases dynamic, they are subject to failure and exceptions arising at runtime. Most of the existing design and implementation notations for crowdsourcing processes do not adequately reflect important features of dynamic crowdsourcing processes. We propose a multi-layered high-level Petri net model (timed-meta ECATNets) to design and control dynamic crowdsourcing processes. In particular, the proposed model makes it possible to adapt crowdsourcing processes in case of task failure. Owing to its use of algebraic Petri nets, the model allows to express compactly: control flow, data flow and time constraints. The proposed model is implemented using Real-Time Maude. The reachability commands and the timed CTL model checker associated to Real-Time Maude could then be used to analyse the correctness of the dynamic and timed behaviours of crowdsourcing processes.
3. Circumvent the proliferation of counterfeited circulars using blockchain
   Organisations issue circulars to declare the decision taken by them to the concerned people. However, in recent times, counterfeiting documents to spread fake information is increasing. In addition, such information is shared as scanned copies on the internet. This accelerates the growth of fake circulars at a rapid rate. Hence, it causes dilemma of whether to believe that the circular is genuine or not. To overcome this, this paper proposes the usage of blockchain technology, and smart contracts embed the digital signature into the document. The proposed approach uses the public key to provide a unique digital identity. It enables any user to sign the circulars using the public identifier, which in turn generates the signature parameters. Further, the documents are stored in decentralised peer-to-peer storage to make them highly accessible and tamper-proof. From the experimental results, it is stated that the proposed approach assures the originality of the document in a significant manner.
4. Blockchain technology: applications, security and privacy, big data, challenges and future directions
   Blockchain technology is transforming industries by enhancing security, transparency, and efficiency. This review explores blockchain's growing relevance and addresses key challenges such as scalability, energy consumption, interoperability, and regulatory compliance, which hinder its widespread adoption. Although prior studies have examined blockchain applications, critical gaps remain. This analysis provides an in-depth review of blockchain in sectors like healthcare, digital identity, AI, and the internet of things (IoT), focusing on unique strengths and limitations. We also examine blockchain's synergy with big data, aiming to uncover new solutions to existing issues. Findings highlight the need for future research on scalability and reliability, outlining a roadmap to address these challenges. Our review seeks to contribute to blockchain's evolution by identifying essential areas for development, ultimately supporting its integration across industries for more efficient, effective solutions.