Blockchain-Based Internet of Things …

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2

Concept of Blockchain Technology

Blockchain is an incorruptible immutable and distributed system. It is just an online

distribution system that can store information, and it is based on interconnected

blocks [29].

2.1

Structure of a Block

Every block contains the following: (i) some data, (ii) the hash of the block, and (iii)

the hash of the previous block (Fig. 1).

Data: The data stored within the block depends on the form of Blockchain. The

data is stored cryptographically. For example, the Bitcoin blockchain stores the infor-

mation of such transactions, such as the source, the recipient, the numbers of coins,

and the transaction’s timestamp [5].

Hash: Every block has a distinctive hash-code (hash). A block is identified by its

hash that is always unique, just as a fingerprint. At the time of the creation of a new

block, its unique hash is generated. Therefore, changing something inside a block

causes the hash to change. If the hash of a block changes, it is no longer the same

block. Thus, hashes are very useful when someone wants to detect the changes of a

block [4].

Hash of the previous block: the tired element inside each block is the previous

block’s hash. That effectively creates a chain of blocks, and it is this technique that

makes a blockchain secure [20].

Fig. 1 Structure of a block