# REISCH: Incorporating Lightweight and Reliable Algorithms into Healthcare Applications of WSNs
## 4 The Proposed Data Collection Scheme
### REISCH's Scheme
#### 4.3.5 REISCH's Protocols
\(CH_{i}\) calculates \(CH_{P}\) which represents the sequence of secret parameters. In addition, \(CH_{i}\) computes \(CH_{A}\) to complete the process of aggregating temporary signatures (\(SigSnT_{3_{s}}\) and \(SigSnT_{4_{s}}\)), random numbers (\(SN_{RNs}\)), and collected data (\(Data_{s}\)). * Finally, \(CH_{i}\) computes \(CH_{m}\) and sends it to the \(LS\). \(LS\) Side
* After \(LS\) sends \(LS_{OTP_{i}}\) for all \(SN_{i}\), it waits to receive \(CH_{m}\) of all \(CH_{i}\) per round. The \(LS\) truncates \(CH_{RN_{i}}\), \(SS_{i}\) and \(CH_{A}\) from each \(CH_{m}\) received. It uses \(SS_{i}\) to reconfigure \(CH_{TS_{2}}\); in addition, the \(LS\) generates a timestamp (\(LS_{TS_{1}}\)) and tests \(\triangle T\) between \(LS_{TS_{1}}\) and \(CH_{TS_{2}}\) to confirm the freshness of the message. * Then, it tests whether \(CH_{RN_{i}}\) matches the value previously sent. If \(CH_{RN_{i}}\) is correct, it is used to determine \(CH_{Pseudi}\) and the latter is used to determine \(CH_{i}\) location (\(CH_{SL_{i}}\)). * Afterwards, the \(LS\) retrieves temporary signatures and random numbers (\(SigSnT_{3_{s}}\), \(SigSnT_{4_{s}}\) and \(SN_{RNs_{s}}\)) from \(CH_{A}\). The \(LS\) uses the \(SigLsE_{i}\) value to specify a \(Parity\) (even/odd) value for all \(SN_{i}\) and \(CH_{i}\). It computes a signature (\(SigLS_{1_{i}}\)) for all \(SN_{i}\) signatures that followed a specific \(CH_{i}\) (\(SigSnT_{3_{s}}\)) and exchange the \(SigLS_{1_{i}}\) segments based on \(CH_{Parity}\). * After that, the \(LS\) calculates \(SigLsT_{1_{i}}\) which equals \(SigChT_{2}\) in \(CH_{i}\) based on \(SigLS_{1_{i}}\oplus SigLsE_{i}\). To ensure the legitimacy of \(CH_{i}\), the \(LS\) extracts the secret parameters at \(CH_{P_{i}}\) and tests the match \(CH_{Pseudi}\) and \(CH_{SL_{i}}\) in the datasets. * At this point, the \(LS\) checks for data integrity collected by \(SN_{i}\). Similarly, the \(LS\) uses \(SN_{RN_{i}}\) to determine \(SN_{Pseudi}\), and performs data signature (\(SigLS_{2_{i}}\)) that equals the \(SigSN\) in \(SN_{i}\) and exchanges the \(SigLS_{2_{i}}\) segments based on \(SN_{Parity_{i}}\). * Next, the \(LS\) uses \(SigSnT_{4_{i}}\) and \(SigLsE_{i}\) to extract \(SigSnE_{i}\). Thereafter, the \(LS\) uses \(SigSnT_{3_{i}}\) and \(SigSnE_{i}\) to compute \(SigLsT_{2_{i}}\). * Finally, the \(LS\) extracts the secret parameters for \(SN_{i}\) from \(SN_{P_{i}}\) and tests matching \(SN_{Pseudi}\) and \(SN_{SL_{i}}\) in datasets. If all signatures and parameters are validated correctly, then that the data collected by \(SN_{i}\) are legitimate and correct and have not been tampered with by the intruder. Protocol 3 between \(LS\) and \(CS\):  
This protocol performs the data storage process (Figure 8 shows the third protocol processes between the \(LS\) and \(CS\) in the data storage). The process is as follows:  
\(LS\) Side  
* In sending case to \(CS\), the \(LS\) initially generates a new pseudonym (\(LS_{Pseud_{n}}\)) and timestamp (\(LS_{TS_{2}}\)) to prepare for the process of sending data to the \(CS\). * Then, the \(LS\) computes the \(SigLS\) signature based on the \(CS\)'s old pseudonym (\(CS_{Pseud_{o}}\)). * After that, the \(LS\) generates and sends \(LS_{OTP}\) to the \(CS\), which is based on the \(SigLS\), \(LS_{Pseud_{n}}\), \(LS_{TS_{2}}\) as well as appending \(SS\) at the end of \(LS_{OTP}\). * In receiving case from \(CS\), \(LS\) truncates parameters embedded within \(CS_{m}\). Thereafter, the \(LS\) generates \(LS_{TS_{3}}\) to check the arrival time of \(CS_{m}\). * Furthermore, the \(LS\) computes \(CS_{OTP}\) that relying mainly on \(LS_{Pseud_{n}}\). Afterwards, the \(LS\) extracts \(CS_{Pseud_{n}}\) to calculate \(SigLS_{3}\). The \(LS\) tests matching \(SigLS_{3}\) and \(SigCS\), and if the result is identical, this means that mutual authentication process between the \(LS\) and \(CS\) is performed correctly and legitimately. * After this stage, the \(LS\) prepares the data storage request to \(CS\).