# ​Consensus Algorithm no.1 — POW

Hello Grabity community ~~~

This is Keunyoung Yun, a software engineer at Grabity. ​

Very nice to meet you through Grabity’s official Medium channel ~~~~

For the people who have not heard of blockchain before,

I would like to explain about the consensus algorithm which is a core structure of blockchain network in this article.

There are three main categories in the consensus algorithm.

This time, I would like to introduce all the three categories, which are PoW, PoS, and DPoS, one by one.

First, let me introduce what PoW (Proof-of-Work) first.

Bitcoin uses PoW for its consensus algorithm.

What Pow means in this context is

​Solving mathematics problems to create new blocks​

In other words, PoW means a process of solving mathematics problems using computing powers such as CPU and GPU to find desired answers ~

​This process using computing powers is also known as ‘mining’.

​People are rewarded for creating new blocks, and the compensation is in the form of the coin (cryptocurrency).​

When you solve problems to create new blocks, the first mined block is only recognized and created,

and other blocks are thrown away to; therefore, it solves a double-payment problem.

​Hmm… for the people who still didn’t understand about the PoW, let me explain with an example.

There are A and B who are using their keys to open a vault filled up with gold.

In this situation, the vault means a mathematics problem, and the speed of putting each key means computing power.

​Therefore, the faster the speed of putting each key is, the more the possibility to open the vault increases.

​In other words, the higher the computing power is, the faster the vault will be open.

​Therefore, if B opened the vault faster than A, B will get the gold for the reward.

Do you understand better?

Now, I would like to talk about the problem of PoW.

There is a waste of energy and electricity problem as people spend too much computing resources to create new blocks,

and difficulty of mining problem as the more people mine, the more difficult it is and the mining will require more computing resources.

​And, there is a cyber-attack called 51% attack,

​Which means if more than half of the blocks are hacked, other blocks will have the data from the hacked blocks.​

I have introduced you some simple explanation about PoW. Next time, I will explain about PoS for the second consensus algorithm.

​Let’s keep it up until you become a blockchain master!

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