Understanding Blockchain.

The Block Chain and Us

In 1903, the Wright brothers invented the airplane. It was hard to imagine then that today over 500,000 people would be travelling in air at any point of time.

In 2008 Satoshi Nakamoto invented the Bitcoin and the Blockchain. For the first time in history his invention made it possible to send money around the globe without Banks, Governments or any other any other two meteorites.
Satoshi is a mystery character and like the Wright brothers he solved the unsolvable problem. Despite its mysterious beginning, the blockchain may be the airplane of our time.

At present it’s like a space rock crashed on Earth. Lot of people around it but very few know what it is.
Blockchain Technology.

It is the chain of blocks that contain information. Blockchain is a distributed ledger that is completely open to anyone. They have interesting property. Once some data has been recorded inside the blockchain it becomes very difficult to change it.

Each block contains Data, Hash of the Block and Hash of the previous Block. The Data that is stored inside the Block depend on the type of Blockchain.

The Bitcoin blockchain for example stores the details about the transaction, such as the sender, the receiver and the amount of coins. A block also has a hash. You can compare a hash to a fingerprint. It identifies a block and all of its contents and its always unique just as a fingerprint. Once a block is created, its hash is being calculated. Changing something inside the block will cause the hash to change, so in other words hash is very important if you want to detect changes in the block. If the fingerprint of a block changes, it is no longer the same block.
The third element in the block is the Hash of the previous block. This effectively creates a chain of blocks and hence makes the blockchain so secure.

But using hash will not prevent tampering. Computers these days are very fast and can calculate thousands of hashes per second which can effectively tamper with the block and recalculate all the hashes of other blocks to make your blockchain valid again.

To medicate this, blockchain is something which is called Proof of Work. It’s a mechanism that slows down the creation of new blocks. In the case of Bitcoin, it takes about 10 mins to calculate the required proof of work and add a new block to the chain. This mechanism makes it nearly impossible to temper with the block.
One more way by which blockchain secure themselves, and that is by being distributing itself. Instead of using a central entity to manage chain, blockchain use peer to peer network and everyone is allowed to join. When someone joins this network, he gets the full copy of blockchain.

So, to successfully temper with blockchain, you need to temper with all the blocks on the chain, rebuild the proof of work for each bock and take control of more than 50% of the peer to peer network. Only then your tempered block becomes accepted by everyone else. So this is almost impossible to do.