Читать книгу Machine Learning Approaches for Convergence of IoT and Blockchain - Группа авторов - Страница 21

In layman’s language we may understand it as a chain of blocks containing information as illustrated in Figure 1.2. The original purpose of blockchain was to time stamp documents however it did not find much application [3]. The blockchain majorly picked up popularity when it was adapted to create a digital cryptocurrency—Bitcoin, by Satoshi Nakamoto in 2009. The most prominent feature of blockchain is that once any information is entered, it is nearly impossible to edit or delete it. Each block in a blockchain has three components associated to it, which are data, hash, and hash of the previous block. The data of a block contains information relevant to the purpose which the chain is utilized for. The next component, i.e., hash is like the finger print of the block and is thus unique to every block. The hash of a block is calculated after the data in entered. Therefore, if the content of any block is tampered with, it, in turn, changes the hash, and hence, it is no longer the same block, and this feature particularly allows us to ensure that any information once entered in a blockchain cannot be modified or deleted. The third component of a block is the hash of the previous block. Each block contains the hash of the previous block which enables the chain formation. If any block in this chain is modified, its hash changes, hence breaking the linkage through the entire length of the chain, disrupting the entire chain formation. This is how the safety and integrity of any blockchain is ensured. The first block of a blockchain is referred to as genesis block.

Figure 1.2 Illustration of blockchain technology.

Let us now understand how blockchain ensures a high level of security. Firstly, since each block contains the hash of the previous block, it is not possible to modify the content of any block without disrupting the chain henceforth. Secondly, this technology follows a practice called proof of work. Hashes are insufficient to ensure protection because computers these days are fast enough to recalculate all the hashes of the blocks within seconds; this is where proof of work comes into the picture. Through this method, we considerably increase the time required to calculate the hash of a single block. These two features when put together enhance the security mechanism. Thirdly, the entire blockchain in available to all its users; in other words, we may say that a blockchain is distributed. This peer-to-peer network enables all members to receive any new block that is formed; it is then verified by each node and is given consensus, only then it is incorporated into the chain. So, in case a block comes up that is tampered with it will be rejected be the other nodes [4]. The benefits of this architecture as observed are tamper-proof nature and better traceability along with resolving trust issues that may otherwise interrupt the supply chain [5]. Blockchain can fall under two categories private and public. A public blockchain is a completely transparent ledger and is decentralized. The information in this platform is encrypted and can be accessed on multiple devices. A public blockchain is nearly impossible to hack, as that will require acceptance from at least 51% of the nodes which is very difficult to attain for a malicious task, as the total number of nodes connected to this chain is very large. In contrast, a private blockchain has a limited audience that can access the content stored on the blockchain. It is an invitation only blockchain and is under the control of a single entity, hence not decentralized. A public blockchain is comparatively more secure than a private one.

Although every user in the network has access to all the blocks, not complete knowledge of any transaction or activity may be gained by all users. The details of all transactions are encrypted. For examples, if user A buys apples from user B via this network, the other users can know that there has been a transaction but would not attain all details, i.e., they may know that there has been a transaction but may not know that is was held for the exchange of apples. Most of the platforms or services that we use today be it Facebook or Google are centralized in nature and they have a lot of control in terms of privacy, and you may not be willing to give any one entity access to all your data. So, blockchain technology overcomes this concern where no one node or entity can have monotonous control or access to any piece of information.

The most common application of blockchain is seen in the cryptographic currency of Bitcoin. Cryptocurrency is a completely digital form of money. A distinctive feature of transaction with Bitcoins is that there is no requirement for a mediating institution. A conventional electronic payment involves third party other than the buyer and seller, usually a bank that facilitates the transfer of money. This technology of Bitcoin eliminates the need of any such mediation. Also, the Bitcoins are decentralized which implies that their distribution and circulation globally can be monitored by a government or any similar organisation. Whenever a bitcoin transaction occurs, the blockchain records the sender’s and receiver’s Bitcoin addresses along with the amount. Each transaction is encrypted with public key cryptography and verified by multiple nodes; these transactions cannot be tampered with. The computers than individuals connect onto this network are referred to as bitcoin miners. The cost of entering into the Bitcoin network is fairly high and bitcoins can only be profitably mined using specialized devices. As the number of nodes in the network increases the difficulty of mining generally increases. What attracts people to bitcoins is to keep their money safe in a bitcoin network as compared to any bank. Some people see it as an investment but there happens to be lot of risk but it is claimed that by 2040 this network will be very well established. Even though we presently seem to observe bitcoins as the only major application of blockchain, a lot of scope beholds for this technology some aspects of which we will be coming across through the course of this chapter [6].

Another growing application of blockchain is the Smart contract. The purpose of smart contract resembles just what a usual contract does i.e., beholds conditions, clauses and agreements. The only difference is that here they are stored as a few lines of code that is kept safe inside a blockchain. Also, this technology allows two parties to bind a contract without the requirement of any third party mediation. These are beneficial and binding as once the details of a smart contract are put in to a blockchain they cannot be modified. We specify the terms and condition of the contact along with the fulfilment condition, this is an efficient means to seal a contract because once made it cannot be manipulated or breached. For example, person A promises to deliver a commodity to person B after exactly 1 year from signing the contract. In this case a smart contract may be brought to effect specifying that the payment made by person B shall only be received by person A on the fulfilment of the contract, till then it may be held as cryptocurrency within the smart contract.

The drawback associated with the bitcoin application of blockchain technology is that the value of a bit coin is highly variable and thus faces a lot of risk. Also this technology demands for very high energy consumption. The data stored in a blockchain is immutable which particularly serves as an advantage and a disadvantage at the same time. Along with these, blockchain technology possesses a high implementation cost. Finally, this technology is not yet standardized or practiced regularly creating an air of ambiguity about it.