# A Secure Opportunistic Network with Efficient Routing for Enhanced Efficiency and Sustainability
## 2 Challenges in Cybersecurity-Driven Opportunistic Networks  
The domain of wireless communication is undergoing a transformative evolution, and at the forefront of this technological revolution stands blockchain, a groundbreaking concept introduced by [PERSON] in 2008 [PERSON] (2008). Anchored by key components such as consensus algorithms and cryptographic techniques, it guarantees tamper-proof data storage and facilitates secure transactions. This section delves into the intricacies of cybersecurity and blockchain technology, unraveling its multifaceted components and shedding light on its profound implications for OppNets. Blockchain serves as the bedrock for secure and auditable data sharing within the context of OppNets [PERSON] (2008). Some studies have investigated the current landscape of cybersecurity training for critical infrastructure protection, focusingon aviation, energy, and nuclear sectors [3]. In the dynamic realm of OppNets, decentralized identity solutions emerge as guardians of secure and privacy-preserving identification [4]. Since OppNets, characterized by high mobility and low density, pose security challenges due to limited power and susceptibility to attacks, trust, rooted in human interaction, plays a crucial role in securing OppNets. This can explore security approaches and techniques to enhance the security levels of OppNets [5]. One study investigated several deployment types for OppNets; complex network properties (average shortest distance, degree distribution, clustering coefficients) were analyzed, and the robustness against wormhole attacks was studied. Results showed wormhole severity depends on node attributes, causing notable impacts on the average shortest distance in specific scenarios. Additionally, security in selective OppNets is observed to be comparatively better than in open OppNets [6]. Moreover, in [7], the authors emphasize the growing need for safeguarding personal devices against security and privacy attacks, with manufacturers increasingly relying on Trusted Execution Environments (TEEs), especially ARM TrustZone in smartphones. Despite TEEs' widespread use, the paper reveals its vulnerability to diverse attacks and provides a comprehensive analysis of existing weaknesses, drawing attention to design flaws. It concludes with effective countermeasures and outlines compelling challenges and open issues, aiming to raise awareness among stakeholders interested in TEE technology. The authors in [8] underscore the growing significance of security in citizens' daily lives, especially with the proliferation of IoT devices, altering the traditional single-device connection model. They highlight the increased attack vectors for potential attackers, examining the concatenation of attacks on various communication protocols (WiFi, Bluetooth LE, GPS, 433 Mhz, and NFC) in a domestic setting. The paper offers a thorough analysis, identifying weaknesses in these protocols, and provides insights into the attacking procedure, along with relevant tips and countermeasures. However, there are still many challenges for cybersecurity and blockchain-driven OppNet systems, and the following list details some of them:  
* _Scalability and Latency_: Challenges such as scalability and latency become more pronounced within the unique context of OppNets [9]. Ongoing research endeavors focus on developing lightweight consensus mechanisms and off-chain solutions, aiming to alleviate these challenges and ensure the seamless functioning of blockchain-driven OppNets [10]. * _Security and Privacy Concerns_: Blockchain, though inherently secure, demands tailored solutions to address the nuanced privacy concerns that arise in the OppNet environment [11]. Cutting-edge cryptographic techniques, such as zero-knowledge proofs and homomorphic encryption, are enlisted to fortify privacy measures and safeguard sensitive information exchanged within the network [12].