Consensus mechanism: Proof of Capacity

Gepubliceerd op 29 mei 2022 om 11:16

This blog discusses another consensus mechanism. Namely, the proof of capacity (PoC). The PoC is a lesser known consensus mechanism but is interesting to discuss. In a nutshell, the PoC is a consensus mechanism involving the deployment of hard disk space.

What is the PoC?

Not many cryptocurrencies use the PoC. As such, it is one of the lesser known consensus mechanisms. Nevertheless, the PoC is an interesting consensus mechanism to discuss. The PoC is also known as the Proof of Space.

The PoC works completely differently from the Proof of Work (PoW) or the Proof of Stake (PoS). The PoC is closest in technique to the PoS consensus mechanism but still differs from each other. In the PoC, the participants of the network (the nodes) can use the available space they have on their hard drive to verify transactions. In the PoS, participants put coins in a staking wallet, while in the PoC hard disk space is used. Because the space available on the hard drive is used, there is also no need for miners to solve a hashing puzzle.

The PoC roughly consists of two steps. These steps are called plotting and mining. In plotting, you have to create a random solution. Plotting is done through an algorithm, namely the Shabal algorithm. All these solutions are stored in the memory (hard drive) of the miner. The miners will then "mine" to obtain the correct solution. The miner who finds the correct solution first gets to verify the transaction on the blockchain.

The more space a miner has on his or her hard drive, the more solutions a miner can store. Because this miner has stored more solutions, this miner also has a higher chance of finding the right solution (generated by the algorithm), and thus can get a reward for the work done.

An example: The miner who has a lot of space on his or her hard drive can store more possible solutions. The chance that this miner has the right solution on his or her hard disk is therefore higher. But the miner must have enough space to store solutions. For this purpose all kinds of equipment can be bought to increase the available space.

Pros and cons of the PoC


  • There is no limitation on the hard drive you use. So the hard drive can be based on Android, Linux etc. The barrier to entry is very low. You also don't have to update the hard drives every time.
  • The biggest advantage to using the PoC is that it is energy efficient. Compared to the PoW, a lot less energy is consumed. Also, anyone can participate and the PoC is very accessible for beginners.

  • It is also a lot more fair compared to the PoW and PoS. It is not how much money you can contribute to a staking wallet, but how much space you make available to the network. The more space you make available to the network, the greater the chance you can get a reward.

  • So it's not like if you use your hard drive for mining, you can never use the hard drive for anything else. The advantage of the PoC is that you can easily and quickly delete all data. Then you can use the hard drive for other purposes.


  • The PoC is a lot less secure, it requires a lot of hard drive space and it is very vulnerable to outside attacks. In addition, hard drives with large amounts of space are not cheap. The PoC is considered fairer than the PoS, but it is also not the case that the PoC is very much fairer. Those who have a lot of money to buy the hard drives with a lot of space have an advantage over those who can not. So even with the PoC, the difference between rich and poor remains visible.

PoC vs PoW 

PoW generally requires more energy to verify transactions on the blockchain. This is because miners compete with each other. So each miner uses as much computing power (and thus energy) as possible to solve the puzzle the fastest. For 1 block, there may be more than 20,000 nodes working to solve the same puzzle. So it takes an awful lot of energy and only 1 miner is rewarded. The rest is left without a reward. These miners have actually worked for nothing. This is not good for the environment and not sustainable either. The energy consumed by the other miners is actually lost. This energy was not used for anything else. El Salvador is now using geothermal energy.

PoC vs PoS

As mentioned earlier, the PoS and PoC are similar. Yet they differ substantially. With the PoS you have to put money in a wallet while with the PoC you have to make space available to the network. It is hard to say which of the two is more fair. In both consensus mechanisms, the miner has to invest a lot of money to have a chance of verifying the transaction on the blockchain. In the PoS through money in a staking wallet and in the PoC also through money, namely buying hard drives with lots of space.

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