## 3 Security and Privacy-Preserving Solutions for IoE
### Blockchain-Based Security Solutions
#### 3.1.3. ZKP Approach for Privacy Protection in IoE-Based Systems  
In IoE systems, billions of devices, users, and services continuously generate data, much of which is sensitive in nature. Personal identities, health data, and location information are processed within these systems, making data protection critical for both individual privacy and system security. At this point, ZKP mechanisms offer a solution by enabling secure authentication in authorization processes without disclosing sensitive information [76]. ZKP allows a user (prover) to prove to another party (verifier) that they possess certain information without revealing the actual content of that information [77; 78]. For example, a user can prove that they have access rights to a system without disclosing personal details such as age, health status, or passwords. As shown in Figure 4, this mechanism ensures that identity remains confidential while still allowing the verifier to complete the authorization process. ZKP protocols are based on three fundamental properties:  
* _Completeness_: If the stated assertion is correct, the verifier always accepts the proof. Mathematically, this can be expressed as: \(\forall x\in\mathrm{L}\), if \(\mathrm{P}(x)\) is honest \(\Rightarrow\mathrm{V}(x)=\mathrm{accept}\), can be expressed as. * _Soundness_: For an incorrect assertion, the probability of a malicious prover convincing the verifier is negligible. This is expressed as: \(\forall x\
ot\in\mathrm{L}\), \(\mathrm{Probability}[\mathrm{V}(x)=\mathrm{accept}]<\epsilon\). * _Zero-Knowledge_: The verifier is convinced of the correctness of the assertion but gains no additional knowledge beyond this fact [78]. Mathematically, it is expressed as. \(\exists\mathrm{S}\): \(\mathrm{S}(x)\approx\mathrm{View}_{\mathrm{v}}(\mathrm{P}(x))\), where \(\mathrm{S}(x)\) denotes the output of a simulator, and \(\mathrm{View}_{\mathrm{v}}(\mathrm{P}(x))\) represents the verifier's view during the actual proof process. These three core properties play a vital role in constructing secure and privacy-preserving access control systems in IoE ecosystems. IoE systems are widely deployed in diverse domains such as healthcare, smart cities, industrial automation, and home automation. In these systems, the main functions of ZKP can be summarized as follows:  
* _User authentication_: Users can authenticate themselves without revealing biometric data. * _Proof of data ownership_: For example, a patient can prove possession of a medical document without sharing its content. * _Access control_: In smart building systems, users can prove they have access rights to certain areas. Different types of ZKP protocols are used in practice, varying in terms of performance, security, and integration aspects [79]. A comparative analysis of common ZKP protocols based on core performance criteria for IoE requirements is presented in Table 5.  
zk-SNARK is suitable for embedded systems, smart cards, and mobile devices due to its small size and fast verification times. However, it requires a trusted setup and is not quantum-resistant. zk-STARK offers quantum security, transparency, and high accuracy. It is ideal for high-security IoE applications, such as smart city systems. Bulletproofs is  
Figure 4: ZKP process in identity verification. compact, requires no setup, and is fast, making it suitable for lightweight devices, wearable technologies, and smart home systems [9; 79; 80]. ZKP mechanisms become even more powerful when integrated with the Confidential Transactions (CT) protocol. This structure enables the verification of transaction correctness while keeping details like amounts and parties confidential. Through the CT-ZKP integration, for example, a user can prove that they have sufficient balance in their wallet without revealing the actual amount, or prove that a condition (such as age >18) is met without disclosing the exact age [81].