From the name, anybody can tell that the blockchain is a chain of blocks. But how are they connected, and how do they function to give the immutability attribute popularly associated with blockchain? This article explains how the blockchain works and how each block is connected.

The Blockchain

Understanding what the blockchain is, is an important step to understanding how blocks are linked in the blockchain. Blockchain is a decentralized public ledger that records transactions in chronological order. Any record or transaction uploaded to the blockchain cannot be changed or altered, ensuring that transactions are secure. A block is the smallest element of a blockchain and serves as a container for all transaction information. A block has four primary properties:

Previous hash: This attribute holds the value of the previous block’s hash, which is how the blocks are connected.

Data: This is the total number of transactions in this block, including those mined and validated.

Nonce: The nonce is a random value used to alter the output of the hash value in a “proof of work” consensus method. The nonce is the parameter used to generate the hash value that every block is meant to generate.

Hash: The digital signature of the block is the hash value derived by running the previous hash value, the data, and the nonce through the SHA-256 algorithm.

The SHA-256 is a cryptographic hash algorithm that generates a unique 256-bit alphanumeric hash value for any given input, which is its distinguishing feature: It will always produce a 256-bit hash, regardless of the input.

How Are Blocks Linked in Blockchain?

Below is a streamlined illustration of how blocks are linked to create a blockchain. Note that each block has a header and many transactions. A fixed-length hash output is produced by hashing the transactions in a block, which is then added to the block header. After creating the first block, each subsequent valid block must include the previous block header’s hash output. Every legitimate block is connected to the blocks that came before it by the chain created from the hash of the previous block header, which is found in every block. Thus, a chain of blocks or blockchain is created by connecting each block to its predecessors.

The chain to the following blocks in the blockchain will be broken if any transaction in a block is altered, even slightly, as this will cause the related hash output to shift dramatically. As a result, the network can quickly identify any change to a block’s contents in the blockchain. Because of this, a transaction that has been added to a block and chained to the blockchain cannot be changed or reversed. As a result, data stored on a blockchain are said to be immutable.

Conclusion

In summary, cryptographical links connect blocks. Blocks are the building blocks of blockchains. A block is a grouping of all transactions that includes the cryptographic hash of the block before it. When a new block is added, a new hash is generated and recorded in the header of the most recent block as well as the header of the block after it, creating a chain. By this point, each block header contains the hashes for the previous and following blocks. Cryptographic links of blocks are a type of chain that blocks use to validate and reach a consensus.

Also, only new blocks can be added to the chain; old blocks cannot be changed. Since a blockchain is a distributed ledger, new blocks are copied throughout the network in order to prevent conflicts. Blockchains are simply distributed immutable digital ledgers of transactions that have been cryptographically signed and are organized into blocks.