Hashing and proof of work

A hash function takes any input and produces a fixed-length fingerprint. Change one character of the input and every character of the output changes. There is no way back: given a fingerprint, the only way to find an input that produces it is to keep guessing.

Data Kaspa mines a block every second.

SHA-256

Add a single space at the end. The fingerprint is completely different, and always exactly 64 characters long.

Which hash function

Kaspa hashes block headers with BLAKE3 and mines with kHeavyHash. These pages use SHA-256 because the family resemblance is what matters for the idea, not the specific function. When you get to writing real transactions, the difference starts to matter.

Mining is a guessing game

A block is its data plus a throwaway number called a nonce. The block counts as mined only when its hash starts with some number of zeros. Nothing predicts which nonce will work, so a miner tries them one after another. That is the work in proof of work — and it is why rewriting a block is expensive rather than merely inconvenient.

Mined

Block

Nonce

Data

Hash

Mine

Type anything into the data field. The block turns red because the hash no longer starts with 0000. Press Mine and watch the nonce climb until it does.

The difficulty here is fixed at four leading zeros so that mining finishes instantly. On the real network, difficulty adjusts continuously to hold the block rate steady as hash power comes and goes.