###### Abstract  
In recent years, cyber-physical systems (CPSs) have gained a lot of attention from academia, industry and government agencies, considered to be the world's third wave of information technology, following computers and the internet. Software-defined networking (SDN) is an emerging technology that can be integrated with CPS to provide scalable, reliable, secure and efficient communication in heterogeneous infrastructures. The increasing importance of blockchain technology has clearly emerged, offering security solutions in various domains, including CPS. Given today's direction of cyber technologies, the goals of CPS, its challenges and the role of SDN and blockchains in CPS need to be identified. Therefore, this Special Issue aimed to invite researchers from academia, industry and government agencies to focus on bringing awareness to security challenges and attacks on the surface of modern cyber-physical systems, and to construct innovative solutions with the help of cutting-edge technologies, such as SDN and blockchains. We especially sought submissions concerning blockchain-based security solutions of critical infrastructures, secure and resilient system architectures, protocols and applications for softwarized CPS environments and SDN capabilities in critical infrastructures, as well as key challenges facing the software-defined CPS of the future. In response, we received a considerable number of submissions, resulting in a total of seven papers being finally accepted. Here, we summarized the contributions of the authors, hailing from various parts of the globe. In the paper \"_Pulverization in Cyber-Physical Systems: Engineering the Self-Organizing Logic Separated from Deployment_\", [PERSON] et al. [1] introduce a novel model for self-organizing CPSs that foster the \"pulverization\" of the structure and execution of global system behaviors, which they define as the ability to decompose macrolevel components and activity into microlevel ones. Additionally, they try to ensure deployment independence, which is the ability to move components and activities with different deployment targets. They validated their approach in a simulation case of pollution-aware household heat monitoring and control systems. In the paper \"_A MILP Model for a Byzantine Fault Tolerant Blockchain Consensus_\", [PERSON] et al. [2] propose a MILP (mixed-integer linear programming) model that behaves similar to a very strong Byzantine adversary, capable of exploring many types of issues in consensus algorithms, including arbitrary network delays and generating intentional failures in an exact manner. The core idea of the paper is an exact adversarial model that explores current limitations for practical blockchain consensus applications, such as dBFT (delegated Byzantine fault tolerance), based on the idea that it can also be extended to other decentralized ledger technologies. In their paper \"_Challenges of PBFT-Inspired Consensus for Blockchain and Enhancements over Neo dBFT_\", [PERSON] et al. [3] explore variants of PBFT (practical Byzantine fault tolerance)-inspired consensus for blockchain, focusing on the dBFT consensus of the Neo blockchain. They discuss various challenges and possible enhancements to mechanisms in this domain. In their paper \"_Improving Transaction Speed and Scalability of Blockchain Systems_ via _Parallel Proof of Work_\", [PERSON] and [PERSON] [4] propose a method to improve the transaction speed and scalability of _permissionless_ blockchain networks driven by proof-of-work (PoW) consensus mechanisms. The proposed method introduces a parallel PoW, in which all miners can together solve the puzzle by taking part in the competition. With the implementation and evaluation of the concept, the authors showed promising results. A hybrid consensus algorithm based on a modified PoP (proof-of-probability) and DPoS (delegated proof of stake) is proposed in \"_Hybrid Consensus Algorithm Based on Modified Proof-of-Probability and DPoS_\" by [PERSON] et al.