An Overview Of Blockchain

Blockchains are very popular nowadays, but many of us have a misconception that blockchain is related to cryptocurrency. That’s not true, blockchains are not scoped as cryptocurrencies but it's far beyond that.

So, let us go ahead and have a look at what exactly a blockchain is, how do they work, what problems they solve, and and how they can be used.


As the name indicates [Block-chain] it can be referred to as a chain of multiple blocks in which blocks contain some information.  Blockchain came into existence in the year 1991 by a group of researchers and was developed to timestamp digital documents so that no one can tamper with the data or make it backdated like a notary, but that feature was not used at that time. Then in 2009 “Satoshi Nakamoto” used the same to create a digital cryptocurrency “BitCoin”.

What is a blockchain?

It can be referred to as a distributed ledger of blocks that is open to anyone and comes with some interesting properties thar make it very difficult to change the data in a blockchain and makes it secure.


What is Data?

Now, the data stored in blockchain defines the type of blockchain; i.e., if it is a bitcoin then the data saved will be something like,

  • From (User) - ID of a person sending the bitcoin
  • To (User) - ID of a person receiving
  • Amount - Amount to be transacted

What is Hash?

Hash is a unique key something like “e25c1bflb55bakf024mlsjgis205azpit402bxci3sjiwwi3”. It is a block identification, so it identifies a block and all of its contents. The hash is always unique just as a fingerprint of an individual. The hash key is generated once the block is created and  with a change of the data in the block, its hash gets changed, so we can know if any data has been tampered with. Hash is very useful to detect the changes in a block

What is the Hash of the previous block?

Hash of the previous block is a hash code that would be generated when the data is being added to the previous block, so it makes a chain of blocks, each block is linked with others making the chain. This is the thing that makes the whole blockchain so secure.

Explaining it in a simpler way,




What is the Genesis Block?

As we can see in the above diagram, the first block does not contain a previous hash key, so this block is called a genesis block. This block can’t use the hash of the previous block because it doesn’t exist.

How is the data in block chains secure?

Taking the same example as above for explaining, let us feed some data to our above blockchain


Now, if I make some changes in [Data 2] let’s say I have Changed “ABC” to “PQR”, then the Hash for the second block will also get changed.




Now, the previous hash of Data [3] is different from the hash of Data [2]. It will make block 3 and all following blocks invalid.