# REISCH: Incorporating Lightweight and Reliable Algorithms into Healthcare Applications of WSNs
## 4 BLAKE family
* **De-identification mechanism** Encryption and k-anonymity mechanisms are applied to hide patients' data. However, these mechanisms suffer from serious-shortcomings. For instance, encryption of collected data [61] has the following drawbacks: \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline
**BLAKE Version** & **Word** & **Message** & **Block** & **MD** & **Salt** & **Round** \\ \hline BLAKE-28 & 32 bits & \textless{}264 & 512 & 224 & 128 & 14 \\ BLAKE-32 & 32 bits & \textless{}264 & 512 & 256 & 128 & 14 \\ BLAKE-48 & 64 bits & \textless{}2128 & 1024 & 384 & 256 & 16 \\ BLAKE-64 & 64 bits & \textless{}2128 & 1024 & 512 & 256 & 16 \\ BLAKE2s/BLAKE2 sp & 32 bits & - & 256 & 128-256 & 64 & 10 \\ BLAKE2b/BLAKE2 bp & 64 bits & - & 512 & 160-512 & 128 & 12 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Versions of BLAKE hash function. Figure 3: Architecture of BLAKE hash function. 1. A temporary HC provider such as a researcher doctor will not benefit from the encrypted data, and, if he/she is able to get the collected data by the decryption process, this is a security weakness in the HWSN system. 2. Huge datasets encryption is dramatically burdening for the \(LS\) system, which causes complexity of operations and processor power consumption [62]. 3. The datasets of collected data perform intensive and continuing operations on medical records such as add, delete, and edit, and, if the records are encrypted, this will multiply the burden on the \(LS\)[63]. 4. Encryption can contain implicitly direct information about the HC patients. The breach of this encryption will expose the patients' information to intruders [64]. The k-anonymity of collected data suffers from the following:  
1. The removal process of all the patients' information obstructs the HC provider from dealing with the linked patients' data [61]. 2. Inserting a large set of false medical records would greatly reduplicate the dataset size. Consequently, this process consumes \(LS\) resources, particularly with the intensive and continuous access of the datasets by HC providers. To address these disadvantages, we use random pseudonyms in REISCH's requests to hide the correlation of patients' information with data. The medical records transmitted/stored among the sensors, \(CH\)s and \(LS\), do not contain any patients' real information. This mechanism prevents the intruders from identifying patients' IDs. In addition, this mechanism is fast and does not need complex operations. When the EMR system wants to add a new HC provider/patient, the REISCH sends a request to the remote servers (\(CS\) and \(AS\)), which provides \(LS\) with the required information about updating random pseudonyms. These random pseudonyms are linked with the users' IDs. This mechanism enables sensors to access and store a specific patients' data without exceeding granted privileges. * **One time passcode (OTP)** OTP is a forceful way of validating sensors in HWSN environments if applied with reliable signature technologies. Using a static passcode/nonce without other validation mechanisms is a security weakness with respect to attacks. Thereupon, OTP presents significant support to the validation process. This mechanism is a countermeasure against replay, MITM, and DoS threats [65]. The intruder cannot utilize this passcode/nonce to authenticate the HWSN later. The sensor sends OTP within a validation request. If the validation process is achieved, the \(LS\) will delete OTP from memory and it will be unacceptable to use it again. OTP provides a strong mechanism to relieve the intruders' risks in the HWSN communications. In REISCH, we apply OTP to get a random nonce with each link to sensors in HC applications to guarantee that only legitimate sensors are communicated to the HWSN. * **Efficient HC data management using XML** The other important part of the proposed EMR system is the repository. The repositories contain data in various contexts since these systems have difficulties dealing with these different coordinates for data.