Proof of Work - why is it hard to find but easy to check?

Miners try again and again

A miner prepares a block it wants to propose.

Then it performs a calculation on the block’s information.

That calculation produces a numeric result.

If the result does not meet the requirement, the miner changes a small piece of information and tries again.

And again.

And again.

A huge number of attempts may be needed before one works.

A miner cannot know in advance which attempt will succeed

The miner cannot predict:

“If I change this value, the next attempt will definitely work.”

Each attempt produces a result that is hard to predict in advance.

So the practical method is simply to try many times.

The result of this calculation is called a hash.

A simple mental model is:

Information goes in → a numeric result comes out

A small change in the input usually produces a very different result.

When does an attempt count as a success?

Each attempt produces a Hash - a number that is difficult to predict beforehand.

Protocol rules define a Target number.

For the attempt to succeed, the Hash has to be lower than the Target.

That is not just an analogy. It is the real underlying idea.

A tiny example:

Imagine possible results from 0 to 99.

If the rule says:

“Anything below 10 succeeds”

then 0 through 9 work - roughly one result out of ten.

If the rule changes to:

“Only results below 2 succeed”

then only 0 or 1 work, so success becomes much harder to find.

In reality the number range is enormous, but the idea is the same:

A lower Target means fewer acceptable results, so more attempts are needed on average.

Hard to find, easy to verify

This is the important part of Proof of Work.

A miner may have performed millions or billions of attempts before finding a valid result.

But when the miner publishes the block, another computer does not need to repeat all those failed attempts.

It performs the required check and asks:

Does this result actually meet the requirement?

If yes, the Proof of Work is valid.

If not, the block is rejected.

More computing power means more attempts

A miner that can perform more calculations each second gets more attempts.

That gives it a higher chance of finding a valid result.

But even a very large miner does not receive a reserved turn.

A small miner can still find the next result.

It simply has fewer attempts compared with the total number of attempts across the network.

The number of mining attempts that can be made per second is called Hashrate.

Who sets the difficulty?

No person sits down and manually chooses the next Target.

The protocol rules already define how it is calculated.

Computers look at how quickly blocks have recently been created and use the same rules to calculate the required difficulty.

If blocks are arriving too quickly compared with the target rate, finding a valid result becomes harder.

If blocks are arriving too slowly, it becomes easier.

This level of difficulty is called Difficulty.

Bitcoin and Kaspa adjust it in different ways and on different schedules, but the idea is the same:

The protocol adjusts difficulty to the amount of computing power on the network so the intended block rate can be maintained.

If a miner tries to use an easier Target than the protocol allows, Nodes can detect and reject the block.

Why use Proof of Work at all?

If every computer could simply say:

“I want to create the next block”

there would be no simple way to decide whose claim should matter.

Counting computers or identities does not solve the problem either.

One person can create thousands of online identities and pretend to be thousands of independent participants.

Proof of Work ties block-finding influence to something that is harder to create for free:

Real computation.

To increase the chance of finding blocks, a miner must perform more attempts, which requires hardware and electricity.

So Bitcoin and Kaspa do not assign influence based on how many names or accounts someone can create.

Block-finding influence is connected to actual computational work.

Proof of Work does not give a miner permission to change the rules

Imagine a very powerful miner finds a block.

Inside it, the miner tries to include a transaction spending someone else’s money without permission.

The block’s Proof of Work may be perfectly valid.

The transaction is still invalid.

Nodes also check the transaction rules.

If the block breaks those rules, they reject it.

So:

Proof of Work gives a miner a chance to propose a block.

It does not give the miner permission to rewrite the network’s rules.

Accumulated work also makes history harder to replace

Every block requires new work.

As more blocks build on a particular history, more work accumulates behind it.

Someone trying to create an alternative history cannot simply edit an old block.

They need to perform enough new work for the alternative history to compete with the one the network is already following.

As more work accumulates, that generally becomes harder and more expensive.

What should you take from this page?

Proof of Work is a competition made of repeated computational attempts.

A valid result is hard to find.

A result that has already been found is easy to verify.

More computing power means more attempts and therefore a higher chance of success.

But even after a miner succeeds, Nodes still verify that the block follows the rules.

And accumulated work helps make accepted history increasingly difficult to replace.