The block header is composed of metadata about that specific block. A block header is utilized to recognize a specific block on a complete blockchain. It is hashed in a repeated manner with the purpose of creating proof of work for mining rewards. As the blockchain comprises of sequences of several blocks that are utilized to store information pertaining to specific transactions occurring on a blockchain network, with the aid of block header, differentiation between the blocks are made.
The blockchain network consists of a unique header. Each block is identified with the aid of block header hash. The specifications of the header include, an 80-byte long string supporting a 4-byte long Bitcoin version number with a 32-byte previous block hash. It also includes a 32-byte long Merkle root supporting a 4-byte long time- stamp with a 4-byte long nonce utilized by the cryptography miners. Along with the above description, the block header includes the following:
- • Cryptographic hash
- • Mining competition
- • Data structure to summarize the transactions in the block
The block identifiers are specifically the cryptographic hash. With these block identifiers, the specific block is said to be identified in a unique manner. Usually, two block identifiers are said to exist—block header hash and block height. As far as block header hash are concerned, the block’s hash is evaluated by each node as soon as the block is received from the network. The second method to obtain a block is via its position in the blockchain, which is simply called as the block height.
The Merkle tree refers to the framework of transactions in the specific block for the corresponding blockchain. The Merkle tree is utilized to store the summary of all transactions in the block and refers to a data structure utilized for summarizing and verifying the dataset integrity containing cryptographic hashes. It is also a method to summarize the entire transactions pertaining to a block, ensuring an efficient process to verify whether a transaction is included in a block or not. Figure 1.3 given below' illustrates a sample blockchain Merkle tree.
Features of Blockchain
Comprehending how a blockchain functions  from technical aspect, the characteristics of blockchain should be understood. There are several things that the block- chain is ready for change. It is reasonable that the Blockchain can really damage multiple institutions and organizations and make the operations more representative, secure, unambiguous, and effective. Blockchain steers an indispensable and disorderly tendency in several fields and aspects. With the growth in the evolution, several intermediaries reduces in number, hence the overall system forms a decentralization form, ensuring security and transparency.
Some of the key characteristics of blockchain is listed below is an adaptable one, in that sense it is said to be altered to fit specific purposes. Figure 1.4 given below shows the blockchain features, followed by which the description about the features are provided.
FIGURE 1.3 Calculating the blocks using Merkle tree.
FIGURE 1.4 Blockchain features.
As shown in Figure 1.4, the blockchain features include:
- • Agreement
- • Dispersed estimation
- • Information repository
- • Source
- • Stability
The descriptive nature of blockchian features are elaborated as follows.
Agreement: The first and foremost feature of blockchain is the agreement. Agreement, as the terms itself defines the potentiality of all the anonymous network users, agreeing the network’s rules and regulations. Besides, whether the rules and regulations are being following by the network users or not are also monitored in a regular basis in the blockchain framework. The agreement in blockchain is said to be arrived at in several means like PoW algorithm or PoS algorithm and so on.
As far as the PoW algorithm is concerned, complex mathematical equations are solved by crypto currency miners. The competing crypto miner whoever solves these complex equations received the block reward, a fraction of digital Bitcoin. On the other hand, the PoS algorithm is validated in a deterministic fashion. Here, the more coins the crypto miner owns a virtual currency, the more the crypto miner is likely to be selected to validate blocks and add to the blockchain.
Dispersed estimation: The second important feature of blockchain is its dispersed estimation. Considering the example scenario of Bitcoin blockchain, each user of the Bitcoin blockchain that is executing a full node will possess an entire copy of the whole blockchain. The copy if composed of the data all the entire transactions recorded on the Bitcoin blockchain.
Upon successful completion of the download, the node are then said to be executed in an independent manner wherein the transactions are processed and are then sent through several nodes across the network. One of the most important aspects about the blockchain’s dispersed estimation is that there is not central node in the network to process and distribute the data. However, every node forming the block in the blockchain is said to be executed in an independent manner.
Information repository: The third paramount feature of blockchain is the information repository. Here, the information repository refers to the information storage area. For example, in Bitcoin blockchain, the information repository here refers to the information related to the Bitcoin transactional data.
Source: Blockchains ensures source in a preprogrammed manner. In conventional type of banking, the customer is aware that the money deposited or the jewels kept in the locker are safe in the bank. However, in case of blockchain transaction, each activity performed by the user is traced, documented and fully identifiable without the aid of third-party required to attest for a specific action to be taken.
Stability: The blockchain transaction are said to be stable because of the reason that it is highly said to be stable. In that sense, the transaction pertaining to blockchain cannot be changed as soon as the transaction is recorded. Even in the case of erroneous record, the record cannot be deleted and is said to be noticeable cannot be deleted. Furthermore, in order to make corrections in the recorded transactions, a new transaction is said to be generated. That generated transaction is then said to refer the erroneous record.