What is cryptocurrancy mining?

Chances are you hear the phrase “bitcoin mining” and your mind begins to wander to the Western fantasy of pickaxes, dirt and striking it rich. As it turns out, that analogy isn’t too far off.

Bitcoin mining is performed by high-powered computers that solve complex computational math problems; these problems are so complex that they cannot be solved by hand and are complicated enough to tax even incredibly powerful computers.

The result of bitcoin mining is twofold. First, when computers solve these complex math problems on the bitcoin network, they produce new bitcoin (not unlike when a mining operation extracts gold from the ground). And second, by solving computational math problems, bitcoin miners make the bitcoin payment network trustworthy and secure by verifying its transaction information.

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When someone sends bitcoin anywhere, it's called a transaction. Transactions made in-store or online are documented by banks, point-of-sale systems, and physical receipts. Bitcoin miners achieve the same thing by clumping transactions together in “blocks” and adding them to a public record called the “blockchain.” Nodes then maintain records of those blocks so that they can be verified into the future.

When bitcoin miners add a new block of transactions to the blockchain, part of their job is to make sure that those transactions are accurate. In particular, bitcoin miners make sure that bitcoin is not being duplicated, a unique quirk of digital currencies called “double-spending.” With printed currencies, counterfeiting is always an issue. But generally, once you spend $20 at the store, that bill is in the clerk’s hands. With digital currency, however, it's a different story.

Digital information can be reproduced relatively easily, so with Bitcoin and other digital currencies, there is a risk that a spender can make a copy of their bitcoin and send it to another party while still holding onto the original.

Special Considerations

Rewarding Bitcoin Miners

With as many as 300,000 purchases and sales occurring in a single day, verifying each of those transactions can be a lot of work for miners. As compensation for their efforts, miners are awarded bitcoin whenever they add a new block of transactions to the blockchain.

The amount of new bitcoin released with each mined block is called the "block reward." The block reward is halved every 210,000 blocks (or roughly every 4 years). In 2009, it was 50. In 2013, it was 25, in 2018 it was 12.5, and in May of 2020, it was halved to 6.25.

This system will continue until around 2140. At that point, miners will be rewarded with fees for processing transactions that network users will pay. These fees ensure that miners still have the incentive to mine and keep the network going. The idea is that competition for these fees will cause them to remain low after halvings are finished.

Verifying Bitcoin Transactions

In order for bitcoin miners to actually earn bitcoin from verifying transactions, two things have to occur. First, they must verify one megabyte (MB) worth of transactions, which can theoretically be as small as one transaction but are more often several thousand, depending on how much data each transaction stores.

Second, in order to add a block of transactions to the blockchain, miners must solve a complex computational math problem, also called a "proof of work." What they're actually doing is trying to come up with a 64-digit hexadecimal number, called a "hash," that is less than or equal to the target hash. Basically, a miner's computer spits out hashes at different rates—megahashes per second (MH/s), gigahashes per second (GH/s), or terahashes per second (TH/s)—depending on the unit, guessing all possible 64-digit numbers until they arrive at a solution. In other words, it's a gamble.

Bitcoin Mining Analogy

Say I tell three friends that I'm thinking of a number between 1 and 100, and I write that number on a piece of paper and seal it in an envelope. My friends don't have to guess the exact number, they just have to be the first person to guess any number that is less than or equal to the number I am thinking of. And there is no limit to how many guesses they get.

Let's say I'm thinking of the number 19. If Friend A guesses 21, they lose because 21>19. If Friend B guesses 16 and Friend C guesses 12, then they've both theoretically arrived at viable answers, because 16<19 and 12<19. There is no 'extra credit' for Friend B, even though B's answer was closer to the target answer of 19.

Now imagine that I pose the 'guess what number I'm thinking of' question, but I'm not asking just three friends, and I'm not thinking of a number between 1 and 100. Rather, I'm asking millions of would-be miners and I'm thinking of a 64-digit hexadecimal number. Now you see that it's going to be extremely hard to guess the right answer.

Not only do bitcoin miners have to come up with the right hash, but they also have to be the first to do it.