# Development of User-Participatory Crowdsensing System for Improved Privacy Preservation
## 3 Proposed System
### Structure of Proposed System  
Table 2 summarizes the relevant notations. Figure 3 shows the structure of the proposed crowdsensing system. It consists of an \(SP\), a pool of data processing nodes (\(P\)), and users (generically denoted by \(u\)). Users may be owners of data requester (\(u_{dr}\)), data provider (\(u_{dp}\)), and data processing nodes (\(u_{no}\)). \(u_{no}\) may have one or more data processing nodes. Each user \(u\) has its own asymmetric  
cryptographic key pair \(\left(K_{pub}(u)\right)\), \(K_{pri}(u)\)) and uses the public key \(\left(K_{pub}(u)\right)\) as its identifier (ID). The difference between the proposed system and existing systems is that the data processing module is moved from the \(SP\) to data processing nodes (\(u_{no}\)) (Figures 1 and 3). (1.2) The \(SP\) assigns a request to a data processing node (\(p_{r}\)), which (3) directly forwards the data received from data provider \((u_{dp})\) to the data requester \((u_{dr})\). (4.2) The \(SP\) rewards the data provider \((u_{dp})\), (4.1) based on the relevant information received from the data processing node. The \(SP\) includes a request database, a data processing node database, a user database, a request management module, and a reward data management module. The request database stores the data requester ID \(K_{pub}(u)\), the request information for sensing data transmitted by the data requester, and the address \(addr(p_{i})\) of the data processing node to which the request is assigned. The data processing node database stores the \(addr(p_{i})\) and \(K_{pub}(u_{no})\) of the corresponding data processing node. The user database maps and manages the ID \(K_{pub}(u)\) of each user and the reward amount \(i(u)\). The request management module forwards the received requests to the appropriate data providers and randomly assigns each request to a node of \(P\). The reward data management module updates the user database using the amount transmitted from the data processing node. The provision request for sensing data includes the description of the requested data, data schema, number of requests, and reward amount. A pool of data processing nodes is a set of computing nodes owned by users who participate in data processing. The data processing nodes perform sensing data processing for the assigned request. Sensing data processing includes data validation, data aggregation, and transmission to a data requester. The computing nodes that constitute the data processing node pool may vary depending on user participation. The proposed system separates validation management in user identification \begin{table}
\begin{tabular}{l c} \hline \hline
**Notation** & **Description** \\ \hline \(P=\{p_{1},\ p_{2},\cdots,\ p_{r}\}\) & Pool of data processing nodes \\ \(addr(p_{i})\) & Address of \(i\)-th data processing node \\ \(u_{dr},\ u_{dp},u_{no}\) & Data requester, data provider, and owner of data processing node, respectively \\ \(D=\{d_{1},\ d_{2},\cdots,\ d_{n}\}\) & Sensing data \\ \(enc(K,d),\ dec(K,d)\) & Encrypted/decrypted data \(d\) with key \(K\) \\ \(i(u)\) & Reward amount of user \(u\)’s incentive amount \\ \(K_{pub}(u)\), \(K_{pri}(u)\) & User \(u\)’s public key (identifier (ID)) and private key of user \(u\) \\ \(K_{\text{ss}}(p,u)\) & Session key for sensing data transport between data processing node \(p\) and user \(u\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Table of notations. Figure 3: Structure of proposed system. for the payment of rewards from sensing data processing and, thus, attackers compromising the \(SP\) can be prevented from obtaining sensitive personal information included in the sensing data (e.g., location information), together with user identification information. Each data processing node includes a session key issuing module and a sensing data processing module.