Proof of Capacity (PoC)

PoC was created in 2015 by Dziembowski and Ateniese. It is also known by various names, such as Proof of Space and Proof of Storage. PoC overcomes the high energy consumption drawn by PoW and favors the rich issue drawn by PoS and PoB. Instead, PoC leverages available hard disk space to allow the mining devices to participate in the network. The more the available hard disk space is, the more chances are to be selected for the next block creation. PoC works in two phases, namely plotting and mining, as follows:

1. Plotting: Plotting is done using a 256-bit variant of Shabal hash, i.e., Shabal256. Depending on the size of the hard disk, plotting creates plot files that consist of the list of nonce values. The calculated hashes are connected into ‘scoops’, consisting of a group of neighboring hashes.

2. Mining: During the mining phase, the miner calculates a scoop number. The miner will utilize the data for scoop number ‘n’ from all the nonces stored in the hard drive and calculate a deadline. After calculating all the deadlines, the miner chooses the shortest deadline. The winner will be that miner who finds the block within the shortest deadline created and gets rewarded.

Applications: Cryptocurrencies such as Burstcoin, Btchd, Diskcoin, and LitecoinHD are based on the PoC algorithm.

Advantages

1. No special hardware needed: The hash function calculation is not compute- intensive and thus, does not require any high computation hardware. It does not require the latest hard disk as well. Any old hard drive can do the task of PoC.

2. Less energy consumption: Mining with hard drives saves 30 times more energy than mining with PoW.

3. Reusability: Once the mining is completed, the hard disk can be wiped out and reused again.

Disadvantages

1. Use of mining malware: Mining malware is used to utilize the disk space and slows down the process of mining. It makes it difficult to understand whether excess hard disk space is used for malicious purposes or not.