Blockchain is one of the most promising and effective technologies for enabling a trusted, secured, and distributed ecosystem. Blockchain-based systems combine cryptography, public key infrastructure, and economic modeling to obtain distributed database synchronization through peer-to-peer networking and decentralized consensus. Blockchain provides solutions to the impediments in smart systems, such as resilience, adaptability, trust, security, and privacy, as well as lower maintenance costs and less support for time-critical applications. The more the digital twin emerges, the greater the risk and challenges in terms of the trust, security, and privacy are there to consider for the designed systems. IoT, machine learning, artificial intelligence, and software analytics are, without a doubt, the critical components of this technological transformation. Among others, immutability, transparency, fault tolerance, and security is not to be overlooked.

Access control, availability and confidentiality, lightweight security and privacy, forensic, data integrity, management and storage, and performance and scalability analysis are among the most highlighted challenges from the trust, security, and privacy perspectives. Meanwhile, cyber-attacks, ransomware, data breaches, and financial information breaches are the most common types of breaches. Apart from, HIPAA, FCRA, FERPA, GLBA, ECPA, COPPA, and VPPA in the USA, the data regulation following the General Data Protection Regulation (GDPR) is now in effect, requiring any organization handling personal data of EU citizens, regardless of location, to comply.

This Special Issue invites theoretical and applied cutting-edge research on standards, frameworks, models, and approaches for security, privacy, and trust management in the diverse and long list of smart applications. Being an active agent in the current technological revolution, the role of blockchain in this solutions paradigm can't be separated. Research covering innovations in tools and techniques for a secured decentralized paradigm of blockchain and its emergence in various domains of life are also encouraged. We welcome original research and review articles.

Potential topics include but are not limited to the following:

• Cases, threat models, protocols, and assisting technologies for blockchain access control, authentication, firewalls, and intrusion detection for networks of smart objects
• Secure collective decision-making and adaptation
• Interface development and Lightweight data structure
• Secure software architectures and middleware in an integrated blockchain environment
• Privacy and anonymity in blockchain and other solutions: threats, mechanisms, guarantees, and policing
• Security, privacy, and trust management in an integrated environment of a digital twin for social networking, energy, smart grid, logistics and supply chain, monetization and e-business, notarization and e-government, healthcare, commerce, insurance, finance and banking, education, learning, crowdsourcing and crowdsensing, and other applications
• Trust, security, and privacy by design and its preservation
• Trust models of blockchain: policy specification, maintenance, and dynamics
• Legal, social, and ethical issues in blockchain – in both developed and developing countries
• Forensic analysis of crime scenes
• Blockchain cybercrime and digital investigation
• Smart algorithms extending machine learning, artificial intelligence, and deep learning for a trusted environment of digital twin
• Tools, techniques, and algorithms for software analytics in digital twin applications