infra- structure for multiple devices to transfer data directly between them using a secure and reliable mechanism. Healthcare IoT applications require high protection to pro- tect the privacy of each patient and prevent tampering with the data collected. The ability to provide a safe exchange of data in a public setting makes the blockchain a perfect candidate for IoT healthcare applications. 7.3.1 BLOCKCHAIN OVERVIEW The blockchain is a sequence of connected blocks where each block records many transactions. Each block has a hash pointing to the previous block forming a blockchain, as shown in Figure 7.3. A block also has a timestamp and a Merkle tree root, a tree hash containing all transactions [9]. All the nodes on the network carry a replica of the whole blockchain. The blockchain structure renders it resistant to tampering. Any modifications to the existing block must change the hash of the block, causing the chain to be invalid. Also, any modifications to a current or new block will cause the root of the Merkle tree to be invalid. Even if the whole chain on one node is tampered with, this would be easily detected since the new chain does not match the replicas found on the other nodes. In this way, medical infor- mation can be exchanged among medical facilities without the possibility of being tampered with. 5G Wireless Communication System in Healthcare Informatics Block Block Block i Hash of Hash of Hash of Block i-1 Timestamp Block i Timestamp Block i+1 Timestamp Merkle Root Merkle Root Merkle Root FIGURE 7.3 Blockchain architecture. Another feature of blockchain technology is the validation of the transaction source. All transactions have a digital signature created using the author's private key. Other users can verify that the author of the transaction uses the author's public key. This function is essential if we want to verify that a surgeon rather than an impostor gives the operating robot commands. In order to compensate for the lack of a centralized transaction verification mechanism, blockchai