What does the term blockchain even mean?
In layman's terms blockchain is basically a database wherein data cannot be manipulated once it is recorded.
Getting a bit more technical blockchain basically means a constantly growing list of records(Blocks) that contains some values inside it and are cryptographically linked which forms the chain of blocks which is why it is named Blockchain.
Now that we have a very simplified overview of the term blockchain let's have a closer look at each block of the chain:
Properties of a block:
- All the blocks in the chain are cryptographically linked to each other using some sort of Hashing Technique. For example, SHA-256 is a famous and commonly used hashing technique in the blockchain.
The blockchain network is decentralized which means that there is no central governing authority that will responsible for all the decisions. Rather a group of nodes makes and maintain the network.
Blockchain has a distributed database as each and every node on the network has and maintains a replica of the version of DB.
Blocks are Immutable Ledger because they are cryptographically linked with each other so, it is impossible to change data inside the block once it is recorded.
As we know the properties of a block let's have a deeper look at the structure of a block inside a blockchain:
In case you are curious to see what an actual block looks like :
As we can see there are 5 items present inside a block which are:
Block Number - This is the serial number of a particular block inside the chain of blocks.
Nonce - Full-form of NONCE is Number Only Used Once which is a value that is unique to each and every block (in case you are wondering this is primarily used for mining).
Data - As the name says this section contains all the data that is stored inside a block such as transactions.
Prev - This field contains the cryptographic hash of the previous node which will be checked every time something is changed inside the chain and if the hash doesn't match the previous one it will reject the changes hence making it immutable.
Hash - This field contains the cryptographic hash generated by encrypting all the above fields of the block itself and will be used in the upcoming block as the previous block's hash.
Just FYI:
- The very first block of a blockchain is called Genisis Block.
- The previous field in the genesis block will always be 0000... as there is nothing previous to the genesis block.
- Hashing is a unidirectional process of encrypting the data which means it can not be decrypted or changed.