Block chain

Online distributed system which store information which are open to everyone. Block chain is collection of blocks, each blocks have data, hash and previous hash. It was developed in 1991 by group of researchers but it was not popular until 2009 when first Crypto currency used this block chain technology called Bitcoin.

3 things in each block:-

1) Data

2) Hash

3) Previous Hash

What is the Genesis Block?

The first block in the blockchain is known as the genesis block. This was built in the year 2009. It is the universal parent of all the blocks in the blockchain. In other words, if people begin at any block and watch the chain counter clock wise then they will ultimately come at the genesis block.

Every node perpetually begins with a blockchain of at least one block because the genesis block cannot be modified. Every node always recognizes the genesis block’s hash and structure. It also recognizes its fixed time when it was created and even its single transaction. Thus, every node has the starting point for the blockchain, a secure “root” from which to build a trusted blockchain. Blockchain technology is a unique invention that has caused the much-required security and protection in the cyber world.

If we changes any block, at that time hash for that block will also change and the next block will invalidate because it has the old hash.

Security

Following are security factors which help blockchain to be fully secure proof so it can not be hampered.

1. Hash :  Hash is like a finger print which is always unique and always generate a unique value.
2. Previous Hash : Current block always have the reference hash code of previous block and this is how block communicate with each other.
3. POW (Proof of Work) : PoW or Proof of work is an algorithm in Block chain network. PoW is used to inject new block in network, where all the users compete to add that block in the network by their at own, after solving some mathematical puzzle. In the end, the user who successfully add the pending block into the network , he or she will get rewarded. This process is also called mining and users are called here as Miners.

4. Consent (Agreement of more than 50% peer): This is another form of security in block chain, if a user want to perform any sort of transaction then this transaction need more than 50% of peer consent to do so. This way it helps any kind of fraud in the network. This is like any election in democratic country, where political party need more than 50% of seats to form their Government. 

Peer to Peer (P2P)

Whenever a new block is added it is been distributed to each of the peers. That means each pair have same copy of that block. When they checkout the block at that time this block is added in the chain. If more than 50% peer does not agree on adding this block in their chain then it won't get added.

So in case if someone try to hack any block, the it has to go through various security checks and it is kind of impossible to manipulate the block chain.

Slow and Steady policy

Now days, our computer system are very fast and it takes only few seconds to recalculate all the block and that way it may manipulate the block chain.

So to make it more secure, they have used slow and steady theory and amount of time to create new block is very slow. In Bitcoin it is 10 min.