Difference between revisions of "Proof-of-Capacity (PoC)"

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Proof-of-Capacity (PoC) is the consensus algorithm, which uses free space on a file storage device (hard disk) to produce the cryptocurrency. The computational power (as with PoW) and number of coins (as with PoS) play no role. Sometimes there is another name for this algorithm - Proof-of-space.


The first time this concept was announced in 2013 by a Polish expert Stefan Dzembowski. Already on August 10th, 2014 at bitcointalk forum was presented Burstcoin coin, which first started using PoC algorithm:

POC btt.png

Other cryptocurrencies on this algorithm appeared a little bit later. The most famous of them are SpaceMint and Chia.


Hard-drive mining differs from PoW-algorithm in that you do not need to buy expensive graphics cards or ASICs, high power supplies and motherboards with a large number of connectors to mine coins. To mine in this way, you need to have the most common notebook with poor parameters and a built-in graphics card.


Instead of regular search of different numerical parameters in the block header and repeated hashing, PoC creates a list of possible solutions on the hard disk when the mining process starts. The more space is allocated on the hard disk, the more possible solutions are stored on the hard disk, which increases the chances of the miner to find the desired value of the hash in its list and get a reward for the block. PoC consists of two stages: dam and mining.

Plotting (preparation for mining)

Before the mining, there's a "hard drive plotting." Its essence is that by repeated hashing of data, which includes the identifier of the miner account, a list with all possible values of nouns is created. Each nouns contains an 8192 hashes, which is numbered from 0 to 8192. Neighboring hashes form pairs called "scoops". So hashes 0 and 1 form a scoop 0, hashes 2 and 3 form a scoop 1 and so on.


Beginning the mining process, the user must calculate the purchase number. For example, the miner starts mining, and the calculation gives it the buyback number 38. Then he must take the buyback number 38 of the first zero and use this buyback data to calculate the deadline. The process is repeated until the "deadlines of all nouns" that are stored on the hard disk are known. After calculating all the deadlines, the user chooses the minimum one of them. A deadline is the number of seconds that must pass after the previous block is created before the miner can start a new block. If no one has created a new block in this time, the maintainer can do so and receive an award. For example, if Miner X has a minimum deadline of 36 seconds and no one has created a new block in that 36 seconds, Miner X will be able to create the next block and receive a reward.


  • Miners can use the cheapest hard drive. It follows that this algorithm initially prevents financial inequality (as is the case with PoW and PoS);
  • Using hard drives is several times more energy efficient than minimizing them with video cards or ASICs;
  • Practically every person on Earth has a hard drive (computers, tablets, smartphones, etc.);
  • No need to constantly update their own equipment.


  • Only a few projects use the PoC algorithm;
  • Proof-of-Capacity is a fairly new algorithm that has not been subjected to heavy loads. Correspondingly, it is possible to detect critical errors during mass usage;
  • In the future, with mass use of PoC, the "geek community" may once again come to the "arms race". Nowadays, for an ordinary person it is enough to have a hard drive of several hundred gigabytes or several terabytes. In the future, this figure may rise to petabytes.

See also