Hash Function

A hash function is to the piece of data as a magician is to a rabbit, producing out of thin air what appears to be an utterly nonsensical string of characters. The result is called a hash, and what is great about it is that even if the initial data was changed slightly, the hash will be absolutely different. This makes hash functions way useful in scenarios such as verifying data or security among other uses especially in the blockchain space. 

In blockchain hash functions are used in creating identification numbers for the transactions and blocks. For instance, Bitcoin employs SHA-256 algorithm while Ethereum employs the Keccak-256 hash function. These functions are like the signature of the blockchain, guaranteeing that each data in the former is not replicated, altered or falsified. The reason for this is that if, for example, someone wanted to alter something in a block, they couldn’t change even a single character in the block without the change in the hash number which would inform everyone that something had been altered.