A blockchain is a series of interconnected blocks that store data. The type of blockchain determines the data that is contained within a block.
A Bitcoin Block, for example, comprises information on the sender, receiver, and the number of bitcoins to be sent.
The Genesis block is the first link in the chain. Each new block in the chain is connected to the one before it.
A hash is also a part of a block. A can be thought of as a unique fingerprint for each block, and it uniquely identifies a block and its contents, similar to a fingerprint. As a result, any change within the block will modify the hash once a block is created.
As a result, the hash is quite helpful in detecting changes in intersections. If a block's fingerprint changes, it is no longer the same block.
Each Block consists of
Hashes are a great way to avoid tampering. Today's computers are fast and it can calculate hundreds of thousands of hashes per second. An attacker can tamper with a block and then recalculate all the hashes of subsequent blocks to make the blockchain valid again in a matter of minutes.
Proof-of-Work is a notion used by blockchains to circumvent this problem. It's a device that slows the production of new blocks.
A proof-of-work problem is a computation that requires a specific amount of effort to solve. However, compared to the effort necessary to solve the computing problem, the time needed to validate the outcomes of the computational problem is negligible.
In the case of Bitcoin, calculating the requisite proof-of-work to add a new block to the chain takes nearly 10 minutes. In our example, if a hacker wanted to change data in Block 2, he'd have to first conduct proof of work before making changes in Block 3 or subsequent blocks.
This approach makes tampering with the blocks difficult, so even if you tamper with one block, you'll have to recalculate the proof-of-work for all subsequent blocks. As a result of hashing and the proof-of-work method, a blockchain is safe.
