INTRODUCTION: its data and it is always unique


Just like
the name suggests, a blockchain is a chain of blocks that contains information.
This method was originally introduced by a group of researchers in 1991 and was
originally designed with the intention to timestamp digital documents so that
it’s not possible to backdate them or to tamper with them. It was almost
designed to be used like a notary. However, sadly, this first introduction of
blockchain went mostly unused until it was adopted in the year 2009 by Satoshi
Nakamoto to create the digital cryptocurrency bitcoin.

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A blockchain
is nothing but a distributed ledger that is completely open to anyone.
Blockchain has an interesting property: once some data has been recorded inside
a blockchain, it becomes very difficult to change it. Here, each block contains
a data, the hash of the block and the hash of the previous block. The data that
is stored inside the block depends upon the type of the blockchain. For
example, blockchain of Bitcoin contains data about a transaction, like the
sender, the receiver and the amount of coins. A block has something called as
hash. A hash is something just like a fingerprint. The hash can identify the
block and its data and it is always unique just like a fingerprint. Once a
block is created the hash has to be calculated. With every change in contents
of blockchain, it’s hash also has to be changed. Hash is something that is very
useful to detect any change in the block. But when the hash of the block
changes even the block changes. The hash of the previous block connects to each
block which makes a blockchain secure. To understand this, let us consider
three blocks. The previous hash of the 2nd block connects to the
present hash of the 1st block. Similarly, the previous hash of 3rd
block connects to the present hash of the 2nd block. In this way, a
chain is created between the blocks called as blockchain. The first block is
the unique block as it is not linked to any previous block. This block is
called as genesis block. For example, let us consider that the hash of 2nd
block is changed, so this new hash of 2nd block does not match with
the previous hash of the 3rd block. Hence, this makes the whole
chain from hereafter invalid. But using hash is not enough to prevent tampering.
Technologies in computer is very fast these days and can calculate hundreds of
thousands of hashes per second. So, this makes tampering of the hashes and then
calculating them again very easy to make the blockchhain valid again. To
prevent from this there is a technique called as proof-of-work. It’s a
mechanism that slows down the creation of the blocks. In the case of
blockchain, it requires around 10 minutes for proof-of-work and to add a new
block to the chain. This mechanism is the best method to prevent tampering in
blockchain. If someone tries to tamper one block, then it will take 10 minutes
to proof-of-work for each block and calculate the new hashes of each block. So,
the technique of hash and proof-of-work is very useful to prevent tampering in
blockchains. Another way to prevent tampering of blockchain is to distribute
the chain. Insted of using a central entity to manage the chain, it is a peer
to peer network and everybody is allowed to join. Whoever joins the P2P network
gets a full copy of the blockchain. The node can use this to verify that
everything is still in order. When someone creates a new block, that new
blockchain is sent to everyone on the network. Each node then verifies that the
chain is not tempered with. If everything is correct, then this chain is added
to their blockchain. All the nodes create a consensus where they discuss which
blocks are valid and which aren’t. Tampered blocks will be rejected by other
nodes in the network. To temper with blockchain, it’ll require more than 50% of
P2P network control.          

are constantly evolving. One of the recent trends is the creation of smart
contracts. These contracts are programs which are stored on blockchains and can
be used to exchange coins based on certain conditions.


Block chain
can be used as an identity system in all the documents such as passports, IDs,
birth certificates, E-residency, etc. Another use can be for digital voting.
With this technology, the voter can check whether his/her vote is successfully
transmitted to their choice of candidate or not with their anonymity being intact.
With voting turnout being low, this technology of online voting can encourage
more people to vote. It can also be used to buy and sell properties and other
valuable assets.


Future of
finance world can be completely revolutionized with use of this technology.
With this technology, a global currency can be set up which can result in
massive reduction of costs all over the world. But to implement this, such an
infrastructure should be developed so that people can easily use it. Also,
people should be taught how to use this technology.