Proof-of-Existence

The foundational use case. PoE creates an immutable, timestamped record for legal documents, contracts, and intellectual property. This provides non-repudiable evidence of creation or possession at a specific moment, which is critical for:

• Legal disputes and copyright claims.
• Patent applications to establish prior art.
• Academic research to timestamp findings. The process involves hashing the document and anchoring that hash to a blockchain, creating a permanent, verifiable proof.

PoE verifies the authenticity and journey of physical goods. By linking a product's digital certificate (hash) to a blockchain at each stage (manufacturing, shipping, delivery), it creates an unforgeable audit trail. This combats counterfeiting and ensures compliance in industries like:

• Luxury goods (watches, handbags).
• Pharmaceuticals and medical supplies.
• Sustainable sourcing for food and materials. Each step's proof is independently verifiable by end consumers.

Ensures critical datasets, such as financial records, sensor logs, or system backups, have not been altered after a certified point in time. Auditors can verify the hash of a dataset against the timestamped proof on-chain. This is essential for:

• Regulatory compliance (e.g., SOX, GDPR).
• Forensic analysis after a security incident.
• Scientific data integrity in long-term studies. It provides a trustless, third-party-verifiable seal for any digital record.

Developers and organizations can publish a cryptographic proof of their software's exact source code or compiled binary at release. This allows users to verify that the software they download is identical to the version that was attested, preventing tampering or supply-chain attacks. Key for:

• Open-source project releases.
• Firmware updates for IoT devices.
• Secure boot processes and integrity measurement. It shifts trust from the distribution server to the immutable proof.

PoE underpins Verifiable Credentials (VCs) in decentralized identity systems. It allows for the issuance of tamper-proof credentials (like diplomas or licenses) where the proof of their validity and issuance time is anchored on a blockchain. This enables:

• Self-sovereign identity where users control their data.
• Instant verification of qualifications by employers.
• Selective disclosure without revealing the underlying document. The proof acts as the trust anchor for the credential's metadata.

Combats deepfakes and misinformation by allowing creators to timestamp and sign original photos, videos, or news articles. The proof can be used to verify the authenticity and original state of media content. This is increasingly used by:

• News agencies and photojournalists.
• Digital artists and NFT creators for provenance.
• Social platforms to label authentic content. Viewers can cryptographically check if media has been altered since its certified timestamp.

The protocol works by generating a cryptographic hash (e.g., SHA-256) of the target data and anchoring this hash in a public blockchain transaction. This creates an immutable timestamp proving the data existed at the time of the transaction. The original data is never stored on-chain, preserving privacy and efficiency. Verification involves re-hashing the data and checking for a matching transaction on the ledger.

• Document Timestamping: Proving the existence of contracts, legal documents, or creative works (patents, manuscripts) at a specific date.
• Data Integrity Verification: Ensuring digital evidence, sensor logs, or scientific data has not been altered after being recorded.
• Prior Art & IP Protection: Establishing an immutable, public record of an idea or invention's creation date.
• Supply Chain Provenance: Creating verifiable checkpoints for digital records of physical goods' journey.

Implementation typically involves:

• Hashing: Using a deterministic function like SHA-256 to create a unique digital fingerprint.
• Anchoring: Embedding the hash in a blockchain transaction (e.g., in an OP_RETURN field on Bitcoin, in event logs on Ethereum).
• Verification Scripts: Tools or smart contracts that allow anyone to submit a file, compute its hash, and check the blockchain for the corresponding proof transaction.

• Proves Existence, Not Ownership: A PoE does not cryptographically link a file to a specific identity.
• Privacy-Preserving: The original content remains private, only its hash is public.
• Immutable but Not Permanent: The proof is as permanent as the underlying blockchain.
• Cannot Prove Uniqueness: It proves a file existed, but not that it was the first or only instance of that content.

• Proof-of-Authenticity: Extends PoE by also verifying the data's origin (e.g., via digital signatures).
• Proof-of-Custody: Proves a party is in possession of a specific piece of data at a given time.
• Timestamping Services: Centralized predecessors like RFC 3161 trusted timestamping.
• Content-Addressable Storage: Systems like IPFS where data is referenced by its hash, inherently proving its existence upon retrieval.

The core function of a Proof-of-Existence. It involves cryptographically binding a piece of data to a specific moment in time, creating an immutable record that the data existed at that point. This is achieved by publishing the cryptographic hash of the data to a public ledger like a blockchain.

• Key Mechanism: The hash, not the data itself, is stored on-chain.
• Primary Use: Providing non-repudiable evidence for intellectual property, legal documents, or scientific discoveries.

The process of creating a persistent, verifiable link between off-chain data and an on-chain transaction. Proof-of-Existence is the most common form of data anchoring.

• How it Works: A cryptographic hash (e.g., SHA-256) of the data is included in a blockchain transaction. Any future verification only requires recomputing the hash of the original data and checking it against the on-chain record.
• Benefit: Enables trustless verification of large datasets without storing the data on-chain, saving significant costs and preserving privacy.

A two-step cryptographic protocol often used in conjunction with Proof-of-Existence for scenarios requiring secrecy before a reveal, such as auctions or voting.

1. Commit Phase: A participant publishes a hash (the commitment) of their secret data (e.g., a bid or vote) to the blockchain. This is a Proof-of-Existence for the commitment.
2. Reveal Phase: Later, the participant reveals the original secret data. Anyone can verify it hashes to the previously committed value.

• Purpose: Prevents front-running and ensures fairness by locking in choices without initially disclosing them.

A data structure that enables efficient and secure verification of large datasets using Proof-of-Existence for a single root hash.

• Structure: Data elements are hashed in a tree, where parent nodes are hashes of their children, culminating in a single Merkle Root.
• Application: The Merkle Root is anchored on-chain. To prove a specific piece of data (e.g., a transaction in a block) was included, one only needs to provide a Merkle Proof—a small set of sibling hashes—rather than the entire dataset. This is fundamental to blockchain light clients and data availability proofs.

The digital equivalent of a notary public's seal, using a blockchain as a decentralized, tamper-proof notary service. Proof-of-Existence provides the technical basis for this.

• Process: A document's hash is submitted to a blockchain, creating a permanent, timestamped record. This record serves as proof that the document was in the signer's possession at the time of the transaction.
• Contrast with Traditional: It proves existence and integrity but does not, by itself, verify the identity of the submitter or the document's contents—those require additional layers (e.g., digital signatures).