The Proof Of Capacity (PoC) has been in circulation since 2014, after being introduced as a basic protocol of the Burst cryptocurrency. It is a consensus algorithm that makes use of the hard disk drive (HDD) of network participants, presenting itself as an eco-friendly alternative to Proof-of-Work (PoW) mining.
Proof of Capacity: how it works
Proof of Work requires expensive, dedicated hardware that is often extremely noisy and energy-intensive, and requires regular repairs or replacements in order to remain competitive.
PoC, on the other hand, uses a very slow hash function known as Shabal. Since Shabal hashes are difficult and slow to calculate, they are pre-composed and stored on the hard disk drive. This process is known as hard disk plotting.
The more solutions are found in the memory, the greater the chances of getting the reward for confirming the block.
Essentially, the proof of work is done in advance in the plotting process and the results of this process are used later to verify each block.
In addition, the confirmation times for a block in Burst are relatively short, with an average of 1 block every 4 minutes. This mechanism allows PoC to achieve enormous savings in efficiency compared to PoW systems.
Pros
It is possible to use any normal hard disk drive on the market thus preventing an unfair advantage caused by the purchase of dedicated equipment, as is the case with Bitcoin ASICs.
HDD usage is several orders of magnitude more energy-efficient than ASIC- and GPU-based mining.
Proof of Capacity is more decentralised because almost everyone has a hard disk drive on their computer or smartphone.
Finally, network participants will not be forced to continually update their equipment.
Cons
Proof of Capacity (PoC) could lead to another arms race. Today, people have hard drives that are in the order of gigabytes or a few terabytes, but in case PoC becomes popular, petabyte discs could appear.
Moreover, it’s a relatively new technology and not rigorously tested in the real world for a long time. The only cryptocurrency with modest volumes to use it is Burst.
