Clear DefinitionsProof-of-Capacity
1 min read
Pronunciation
[proof uhv kuh-pas-i-tee]
Analogy
Imagine a lottery where, instead of buying tickets with money, you buy tickets by dedicating shelf space in your warehouse (hard drive space) to storing special, pre-printed lottery numbers (plots). The more shelf space you dedicate and fill with these numbers, the more chances you have of your stored numbers being called to win the right to create the next block. It's less about quick calculations and more about how much data you can store and quickly access.
Definition
A consensus mechanism where mining rights are allocated based on the amount of hard drive storage space (capacity) a participant dedicates to the network. Miners pre-compute and store large datasets called 'plots' on their hard drives, and the right to mine a block is determined by how efficiently they can access these plots.
Key Points Intro
PoC (also known as Proof-of-Space) leverages storage capacity as the scarce resource for achieving consensus.
Key Points
Miners allocate hard drive space to store large datasets (plots).
The mining process involves efficiently searching these plots for a solution to a challenge.
Generally more energy-efficient than PoW as the primary resource is storage, not computation speed.
Aims to make mining more accessible to users with standard hardware (hard drives).
Example
Burstcoin (now Signum) was one of the first cryptocurrencies to implement Proof-of-Capacity. Chia Network uses a related concept called Proof-of-Space and Time.
Technical Deep Dive
In PoC, the plotting phase involves generating large cryptographic datasets using a hash function and a private key. These plots are stored on the miner's hard drive. For each block, a challenge is derived. Miners then scan their plots to find a 'proof' (e.g., a hash that meets certain criteria when combined with the challenge). The miner who finds the best proof (often the one with the smallest resulting hash or shortest deadline) gets to mine the block. The 'Proof-of-Space' aspect refers to the storage itself, while 'Proof-of-Time' (as in Chia) adds a Verifiable Delay Function to ensure time passes between blocks and to prevent certain grinding attacks.
Security Warning
PoC systems can be vulnerable to 'plot grinding' attacks if not designed carefully, where miners try to optimize their plots for specific future challenges. The true decentralization can also be affected if large entities can amass vast amounts of storage more cheaply than individuals. Data durability and drive failure are also operational concerns for miners.
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