Blockchain Developer's Guide

Hashing a block

In the PoW systems, new entries to a blockchain require hashes to be computed. In Bitcoin, miners must compute two SHA-256 hashes on the current transactions in the block—and included therein is the hash of the previous block.

This is pretty straightforward for a hashing algorithm. Let’s briefly reiterate: an ideal hash function takes the expected input and then outputs a unique hash. It is deterministic. There is only one possible output and it is impossible (or computationally improbable) to achieve that output with a different input. These properties ensure that miners can process a block and that each miner can return the same result. It is through hashing that Blockchains attain two properties that are crucial to their ...