Filecoin Storage Proof

A zero-knowledge proof that cryptographically verifies a storage provider has created a unique, physically independent copy (replica) of a client's data. This prevents providers from deduplicating or faking storage commitments.

• Purpose: Proves unique, on-disk storage.
• Process: Involves a computationally intensive sealing process to encode the data.
• Result: Generates a CommR (Replica Commitment) for the stored data segment.

The ongoing proof that a storage provider continues to store the data they committed to, over a period of time (spacetime). It is the core of Filecoin's storage consensus.

• WindowPoSt: Submitted by providers every 24 hours for each sector. Failure results in penalties and eventual sector termination.
• WinningPoSt: Submitted by block-producing providers to create new blocks, proving they are actively maintaining storage.

A mechanism to subsidize and prioritize storage of socially valuable data. Verified Clients are entities granted DataCap (a resource allowance) by Notaries in the Verified Registry.

• Incentive: Storage deals with Verified Clients earn a 10x multiplier on block rewards for the provider.
• Goal: Aligns economic rewards with the network's mission to store useful data.

The end-to-end process for storing data on Filecoin, managed by smart contracts on the blockchain.

• Deal Making: Client and provider agree on terms (duration, price) via the Storage Market.
• Sealing: Provider encodes data into a sector and submits PoRep.
• Proving: Provider continuously submits PoSts for the sector's duration.
• Termination: Sector expires or is terminated, freeing storage capacity.

The peer-to-peer market for fetching stored data. It operates off-chain with micropayments for speed and efficiency.

• Protocol: Uses Graphsync or Bitswap for data transfer.
• Payment: Payment channels (like state channels) enable pay-as-you-go retrieval.
• Focus: Optimized for low latency and high bandwidth, separate from the proving layer.

The penalty system that enforces storage reliability. If a provider fails to prove storage (fault), they are penalized.

• Fault Fee: A small, continuous penalty for a faulty sector.
• Termination Fee: A larger penalty for a provider voluntarily terminating a deal or failing to recover from a fault. A portion of the provider's initial pledge collateral is slashed.

A Proof-of-Replication (PoRep) is a cryptographic proof that a storage provider has physically allocated a unique, independent copy of a client's data. It prevents a provider from storing only one copy while claiming to store multiple redundant copies. Filecoin's PoRep uses sealing, an intensive process that encodes the data into a unique replica, binding it to the provider's physical hardware.

• Purpose: Prove unique physical storage.
• Key Mechanism: Data sealing and sector commitment.
• Frequency: Executed once when data is initially stored.

A Proof-of-Spacetime (PoSt) is a proof that a storage provider has continuously and correctly stored a specific piece of data over a defined period. It is the core of Filecoin's ongoing verification. There are two main types:

• WindowPoSt: Submitted regularly (e.g., daily) for all active sectors. Failure results in penalties.
• WinningPoSt: Submitted when a provider wins the right to create a new block, proving storage for a randomly selected sector.

PoSt ensures persistent storage and is secured by cryptographic challenges.

DataCap is a resource allocated to Verified Clients through a decentralized notary system. Clients with DataCap can make verified deals, which incentivize storage providers with higher block rewards compared to regular deals. This mechanism aligns economic rewards with the storage of socially valuable data.

• Purpose: Subsidize and prioritize useful data storage.
• Process: Clients apply to community-notaries for DataCap allocation.
• Impact: Drives storage of datasets for research, science, and public goods.

A storage deal on Filepin follows a defined lifecycle tied to cryptographic proofs:

1. Deal Proposal: Client and provider agree on terms (duration, price).
2. Publishing & Sealing: Deal is published on-chain. Provider performs PoRep to seal data into a sector.
3. Active Storage: Provider submits periodic Proof-of-Spacetime (PoSt) to prove continuous storage.
4. Completion/Expiration: Deal ends; sector can be terminated or upgraded.

Failed proofs trigger slashing of the provider's staked collateral.

Filecoin uses zk-SNARKs (Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge) to drastically compress the size and verification time of its storage proofs. The outputs of Proof-of-Replication and Proof-of-Spacetime are wrapped into a single, small zk-SNARK proof.

• Benefit: Enables lightweight on-chain verification. A complex proof is reduced to a ~200-byte snapshot.
• Efficiency: Makes the blockchain scalable by minimizing the data needed to validate storage claims.

The Fault system detects and penalizes storage providers who fail to submit valid proofs. A sector is marked faulty if a WindowPoSt is missed or invalid. Key concepts:

• Fault Fee: A penalty incurred for each day a sector remains faulty.
• Termination Fee: A larger penalty if a provider voluntarily terminates a deal early or fails to recover a faulty sector.
• Slashing: The burning of a portion of the provider's initial pledge collateral and block rewards as a disincentive for malicious behavior.

A Proof-of-Replication is a cryptographic proof that a storage provider has created a unique, physically independent copy (replica) of a client's data. It prevents providers from deduplicating data across multiple clients and ensures the promised redundancy. The process involves sealing the data into a unique format, which is computationally intensive and proves a specific storage commitment.

A Proof-of-Spacetime is a proof that a storage provider has continuously stored a client's data for a specified period. Providers must submit these proofs to the network at random intervals. There are two main types:

• WindowPoSt: Submitted daily for all sectors, with penalties for failure.
• WinningPoSt: Submitted for a randomly selected sector when creating a new block, rewarding consistent uptime. This mechanism ensures persistent storage and network security.

A Data Deal is a verifiable agreement, recorded on the Filecoin blockchain, between a client and a storage provider. It specifies the terms of storage, including:

• Duration of the storage contract.
• Price paid in FIL tokens.
• Replication factor (number of copies). The deal's lifecycle—from proposal and funding to activation and completion—is managed on-chain, enabling a trustless and programmable storage market.

The Retrieval Market is a secondary, off-chain peer-to-peer network for quickly fetching stored data. Unlike the storage deal process, retrieval is designed for low-latency access. Retrieval providers (who can be separate from storage providers) compete to serve content, with payments typically using micropayment channels for pay-as-you-deliver streaming. This separates the economics of long-term storage from fast data access.

Filecoin's verifiable storage supports applications requiring provable data integrity and long-term preservation:

• Web3 & NFTs: Storing the underlying media files (images, video) for NFT collections with immutable proof.
• Scientific Datasets: Archiving research data with cryptographic guarantees against loss or tampering.
• Data Archival: Providing a cost-effective, decentralized alternative to traditional cloud storage for historical records.
• Video Streaming: Platforms using the retrieval market for decentralized content delivery.

A cryptographic proof that a storage provider has physically stored a unique, encoded copy of a client's data. It prevents providers from claiming to store more data than they actually have by proving the data was stored at the time of sealing.

• Purpose: Verifies unique, persistent storage.
• Mechanism: Computationally intensive encoding process creates a unique 'replica'.
• Security: Makes it economically infeasible to fake storage commitments.

A cryptographic proof that a storage provider is continuously storing a client's data over a period of time. It is the ongoing verification mechanism that replaces traditional Proof-of-Work in Filecoin.

• Purpose: Provides continuous, verifiable proof of storage.
• Types: WindowPoSt (frequent, mandatory checks) and WinningPoSt (for block rewards).
• Penalty: Failure to submit a valid WindowPoSt results in slashing of collateral and loss of stored sectors.

A cryptographic agreement between a client and a storage provider, defining terms like price, duration, and replication. Providers must lock collateral (in FIL) to participate.

• Collateral Types: Initial Pledge Collateral (to join network) and Deal Collateral (for specific deals).
• Slashing: Collateral is forfeited if a provider fails proofs or goes offline.
• Incentive: Aligns provider's economic stake with reliable service.

The network's automated mechanism for detecting when a storage provider fails (becomes faulty) and applying economic penalties. This ensures data durability and provider accountability.

• Faults: Occur when a sector is unavailable for PoSt.
• Penalties: Include sector termination fees and loss of block rewards.
• Recovery: Providers can declare and recover from faults within a grace period to avoid termination.

Filecoin's proofs rely on zk-SNARKs (Zero-Knowledge Succinct Non-Interactive Arguments of Knowledge), which require a secure initial parameter generation ceremony.

• Trusted Setup: The 'Phase2 Powers of Tau' ceremony involved global participants to generate secure parameters.
• Efficiency: zk-SNARKs allow for tiny, quickly verifiable proofs of large computations (PoRep/PoSt).
• Foundation: This setup underpins the entire network's security and must remain uncompromised.

The synergy of incentives and disincentives that secure the network. It makes honest storage more profitable than cheating through a combination of block rewards, fees, and slashing.

• Block Rewards: Incentive for providing reliable storage over time.
• Deal Fees: Direct payment from clients for storage and retrieval.
• Security Guarantee: The cost of acquiring and locking collateral, plus potential slashing, must exceed any potential gain from cheating.