## 3 Security and Privacy Challenges
### Mitigation Strategies Against EC Security Challenges
Blockchain governs protocols that collaboratively make judgments involving transaction execution, exercising mechanisms such as voting and consensus algorithms [7]. Blockchain is a distributed and secured ledger technology based on the zero-trust architecture, offering a strong shield against data privacy and security threats [131]. Blockchains are integrated into EC that documents transactions in an increasing chain of blocks [132; 133]. As shown in Figure 8, each block is connected to the previous one by referencing its cryptographic hash value, except the first block, the genesis block. Each block contains a significant piece of information like the previous hash, timestamp, counter-like mechanism for every hash estimation called a nonce, Merkle root representing the hash of all the transaction hashes, and transactions (Tx) for a specific time [134]. Consensus algorithms enthuse trust in the network through an agreement among the validated nodes while deciding to generate newer blocks into the blockchain [30]. [PERSON] et al. proposed a blockchain-enabled Platform-as-a-Service (PaaS) model that ensures data integrity and security of mobile users in an IoT environment [135]. The behavior detection of blockchain nodes using a technique called T2A2 vec is carried out in [136] by extracting node account features, transaction time, transaction type, and transaction amount. The T2A2 vec technique counters tampering of transaction records and carries out authentication of blockchain nodes. BeCome is a blockchain-enabled computation offloading measure used in [137] to ensure data integrity in EC. Also, a nondominated sorting genetic algorithm III (NSGA-III), additive weighting (SAW), and multicriteria decision-making (MCDM) are proposed for optimal resource allocation and offloading strategy. [PERSON] et al. have adopted a Lightweight Blockchain-enabled RFID-based Authentication Protocol for Supply Chains (LBRAPS) that offers secured and real-time authentication through the integration of blockchain, RFID techniques, and 5G MEC [138]. A decentralized and tamper-proof system using Vickrey-Clarke-Groves (VCG) auction theory is proposed for inducing trust in a collaborative EC while optimizing resource allocation and load balancing [139]. A blockchain-based secured data aggregation (BSDA) approach is used in mobile data collectors (MDCs) for task management and framing of block generation rules [28]. [PERSON] et al. integrated blockchain, certificateless cryptography, elliptic curve cryptography, and pseudonym-based cryptography methods in a mutual authentication scheme between the edge servers and devices citecheng2021 blockchain. Electronic Health Record (EHR) security is ensured by integrating blockchains in EC while storing users' data locally on edge devices [140]. A blockchain user or miner estimates a hash value by solving a computationally intensive proof of work (PoW) linking any two immediate blocks after neighboring miners reach a consensus. However, roadblocks are met in resource-limited nodes of the EC network unable to undertake the mining and consensus process [141]. * _Intrusion Detection System (IDS)_: In EC networks, intrusion detection systems (IDSs) can play a critical role in detecting malicious actions or attacks. IDSs investigate data traffic and resource utilization, issuing alerts when suspicious behavior is detected. IDSs can be characterized into two groups based on their intrusion detection strategies: signature-based and anomaly-based. Signature-based IDSs cross-check monitoredevents with a database of known intrusion techniques to identify potential threats. In contrast, anomaly-based IDSs learn the normal activities of the system and report any abnormalities or inconsistent events [71]. [PERSON] et al. and [PERSON] et al. discuss supervised and unsupervised ML models for IDSs for the detection of anomalies in IoT networks and deployment challenges of this ML on constrained edge devices [71; 74].