Blockchain and Big Data in the Healthcare Sector


The blockchain technology came into existence in the financial sector with the arrival of the cryptocurrency Bitcoin in 2008. Since then the technology has emerged multiple folds, and the technology along with other concepts is getting into various sectors. A blockchain can be considered as a structured database like a linked list, with all the data nodes connected to each other with a pointer.

A blockchain technology will be very useful where all the nodes in a network want to share their work and information on a common platform. Bringing the multiple authoritative domain on this single platform will make them work in a trusted environment so that they can cooperate, coordinate and collaborate (Vedpal et al., 2012) with each other in a decision-making process in the network.

In the traditional way of sharing the documents, one person writes a document that might contain some data or information and sends it to the receiver. The receiver again writes some data on that and then sends it back to the sender. With this kind of sharing there is a lot of time consumed, and the sender and receiver are not able to write the document simultaneously. Also, if the number of users will be more in this kind of network, it might take a huge amount of time. Now if we use some Google document application for sharing the information, the time will cut down to very less but again the problem is with the single or central authority. First, the network is still not decentralized and suffers from a single point of failure. This could be a problem if the central authority goes down or the server crashes. Second, every user needs sufficient bandwidth for the simultaneous update of the document. So, these are some of the disadvantage of a centralized system and necessity of moving the system on a decentralized system.

A blockchain technology is a distributed and decentralized technology. Distributed means everyone in the network collectively executes the job. Blockchain is based on the concept of distributed ledger technology (DLT) and is known as one of the types of DLT. In the blockchain technology there is no centralized/single authority or a node that has complete control over the chain, thus called as a decentralized technology in which there are multiple points of coordination. A network created using a block- chain technology is a tamper-evident and tamper-proof network. A blockchain is a digitally implemented network as all the records in a blockchain network are secured cryptographically.

In the blockchain network every node in the network maintains a local copy of the complete information. A decentralized system must ensure the consistency in the local copies with the node present in the chain so that the copies at every node are identical with all other copies on other nodes. Thus, all the local copies are getting updated based on the global information in the network.


Figure 9.1 shows a typical blockchain process, in this case a transaction made by a user. The transaction could be of any type; it could be a financial transaction, or it could be just sharing information to the other nodes of the network. It is to note that all the nodes connected in the network have a ledger with them, which is a decentralized ledger and is used to store every transaction happening in the network. This means whatever transaction is happening in the network it will be updated to all the node present. Any node that wants to create a transaction has to write the transaction in a block. A block is a kind of container that can take up around 500 transactions on an average, although the size of a block is just up to 1 MB (Madeira, 2016). Once a node finishes a transaction, this information is added in the block. This newly created block will get a new block number and a unique ID attached to the block. This unique ID is known as a hash value. A hash value is a value created by the hash function, which is to make a transaction secure. This newly created block is now going to into the blockchain network where all other nodes are present, whose duty is to verify and validate the newly created block. Now' if the transaction made in the block is correct and authentic and also has no false information, the transaction got accepted by the nodes of the network and based on a consensus algorithm applied on the blockchain by the creator of the network. Once a transaction is validated by the nodes, the valid block gets added into the block. All the blocks that got validated are added one after the another and form a chain called a blockchain. All the blocks that are added in the chain have their ow'n hash value, and the hash value of the previous block makes all the blocks connected with each other. The first block in the chain has its own hash value and does not have the hash value of previous block. This first block in the chain of blocks is called as genesis block.

Blockchain process

FIGURE 9.1 Blockchain process,

A blockchain works like a public ledger, which means anyone can join this type of blockchain. When a transaction is created by some node during that time it should ensure that this particular transaction, if it is a valid transaction, should get committed to the existing public ledger or blockchain; otherwise, that entry will not be there in the blockchain. Once the transaction is verified and validated by the other nodes of the network all the information should be consistent and get updated on all the local copies. The blockchain has to be secure enough that once the information is updated on all the nodes, no one could modify the data present in the nodes, or if some node is modified in the data and broadcast the information in the network, other nodes should be capable of detecting that there is some change in the data and the information must not be included. The privacy and authenticity are other important factors of a blockchain that need to be ensured as the data belongs to different clients.

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