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Blockchain – Chaining Blocks

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  • Last Updated : 20 Oct, 2021

Blockchain is the backbone Technology of Digital CryptoCurrency BitCoin. In its most basic definition, blockchain records how a digital asset has been accumulated in a distributed, decentralized fashion. They are designed to prevent data modification, making them an ideal disruptor for industries including payments, cybersecurity, agriculture, and healthcare. Blocks are records linked together by cryptography in a blockchain. In addition to a cryptographic hash of the previous block and the timestamp, each block contains transaction data.

This chain of blocks is what is referred to as a truly distributed ledger, as it is made up of the blocks created by various miners. There are some basic terminologies in blockchain like:

  1. Block: In a Blockchain, a block represents the ‘present’ and contains information about the past and future of the network.
  2. Hash: Hash functions are used in Blockchains to secure encrypted demands that are required for a blockchain to work.

Block Chaining

The records which are stored within blocks are immutable and verifiable. Now, let’s take a look at some records which are stored in a blockchain. It can be noticed from the diagram that records have been split into a number of different blocks-

In order to ensure a sequencing of the blocks, these are in fact, chained together, and it is a mechanism of this chaining that ensures not only an ordering of the blocks but also the immutability and verifiability of the records within them.

Features of Chaining Blocks:

  1. There is a cryptography link between adjacent chains.
  2. Each block in a blockchain includes a cryptography hash of the previous block.
  3. It also includes the timestamp of the block (when the block was added to the Blockchain). And in the case of Ethereum, it includes all the Transaction data.
  4. If any individual Transaction which makes up a block has been modified then the hash of that block will be very different from what it was previously. In this way, the cryptographic Link between adjacent blocks will be broken.
  5. Because of the cryptographic link, any transaction data that has been written into the blockchain cannot be modified after the fact.
  6. Any node can try to verify the entire blockchain by producing a hash of the very first block and then making sure that those hash contents are present in the second block and the whole process keeps repeating until all the blocks have been verified.

What Happens When Transaction Content Changes?

If there is a need to change the contents of one transaction, in one of the previous blocks in the blockchain, then just re-compute the hash for that block and after that, include that modified block hash in the next block as well.  For the next block, if the hash of the previous block has changed then its own hash block will be different, so the hash for that block will also need to be recomputed. In fact, if there is a requirement to change any of the previous transactions written to the blockchain, then it is required to recompute the hash for every single block. and this is something that is not trivial because you will have to reach a consensus among all the nodes which participate in the Blockchain network. Each and every transaction in the Blockchain is both verifiable and immutable or permanent.

Each block in the blockchain contains multiple transactions and the hash of the previous block is added to the current block when making a chain of blocks.

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