EntityMap — Gridcoin Blockchain Stamping

An entity-first index of what Gridcoin Blockchain Stamping knows, published for AI systems and retrieval pipelines under the EntityMap v1.0 standard. Machine-readable version: entitymap.json.

Generated 2026-07-20T00:00:00Z · 8 entities

Gridcoin Blockchain Stamping Service

A free Proof of Existence service that permanently certifies documents on the Gridcoin blockchain. Files never leave the browser — only their SHA-256 hash is stored on-chain.

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Evidence

Gridcoin Blockchain Stamping is a free Proof of Existence service. Users drop a file in the browser, a SHA-256 hash is computed client-side, and the hash is embedded in a Gridcoin blockchain transaction using OP_RETURN. The file never uploads. Once confirmed, the proof is permanent and publicly verifiable.

Gridcoin Blockchain Stamping

Documents are never uploaded — only the SHA-256 hash is transmitted. No user accounts or personal data are collected, no tracking pixels are used, and the service is also available via a Tor onion service.

Gridcoin Blockchain Stamping :: About

Proof of Existence Concept

A technique that uses an immutable public blockchain to prove that a specific piece of data existed at a certain point in time. Once embedded and confirmed, the data cannot be altered or removed.

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Evidence

Proof of Existence leverages blockchain technology to prove that a specific piece of data existed at a certain point in time. Because the blockchain is an immutable, decentralized public ledger, any data embedded in it cannot be altered or removed after confirmation.

Gridcoin Blockchain Stamping :: About

SHA-256 Standard

A cryptographic hash function that maps a file of any size to a fixed 64-character hexadecimal digest. The stamping service computes this digest in the browser, so the file itself is never transmitted.

Same as: https://en.wikipedia.org/wiki/SHA-2

Evidence

The file's SHA-256 hash is computed entirely client-side using js-sha256 — the file never leaves the user's device. Only the resulting hash is submitted to the stamping service.

Gridcoin Blockchain Stamping :: About

Gridcoin Platform

The decentralized blockchain network that stores stamp hashes. Each stamp transaction embeds the hash in an OP_RETURN output; once confirmed it is permanent and publicly verifiable.

Same as: https://en.wikipedia.org/wiki/Gridcoin

Evidence

The service embeds the hash in a Gridcoin blockchain transaction using an OP_RETURN script opcode. Once the transaction is confirmed on the blockchain, the proof is permanent and publicly verifiable.

Gridcoin Blockchain Stamping :: About

Gridcoin Stamp Protocol Concept

The on-chain data format for stamps. Each OP_RETURN payload carries a "5ea1ed" ("Sealed") identifier word, a protocol version, and up to two SHA-256 hashes.

Also known as: 5ea1ed OP_RETURN stamp format

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Evidence

The hash is embedded using OP_RETURN. The payload begins with 6a46 (the OP_RETURN prefix) and the identifier word 5ea1ed ("Sealed"), followed by a protocol version and up to two 64-character SHA-256 hashes. Storing two hashes per transaction saves on fees.

Gridcoin Blockchain Stamping :: About

Stamping API Service

A public, unauthenticated, CORS-enabled JSON:API for creating stamps, looking up hashes, and querying the service wallet.

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Evidence

The API is public, unauthenticated, and CORS-enabled, following the JSON:API specification. Endpoints let callers create stamps, fetch a stamp by id, look up the earliest stamp for a hash, and read the service wallet balance.

Gridcoin Blockchain Stamping :: API Reference

Gridcoin Stamp GitHub Action SoftwareProduct

A GitHub Action that anchors release assets to the Gridcoin blockchain on every published release, appending a verification table to the release notes.

Same as: https://github.com/gridcat/gridcoin-stamp-action

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Evidence

The Gridcoin Stamp Action anchors GitHub release assets to the Gridcoin blockchain on every "release: published" event. It computes the SHA-256 of every artifact on the runner, submits the hashes to the stamping API, and writes a "Blockchain Timestamps" table into the release body with a verification link per file.

Gridcoin Blockchain Stamping :: GitHub Action for CI/CD

Blockchain Proof Certificate Service

A public verification page and printable one-page PDF certificate for a confirmed stamp, carrying the hash, transaction id, block, UTC timestamp, and a QR code linking back to the proof.

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Evidence

Each confirmed stamp has a verification page at /proof/{hash} and a printable PDF certificate that includes the SHA-256 hash, transaction id, block, UTC timestamp, and a QR code, plus instructions for verifying the proof against any Gridcoin block explorer.

Gridcoin Blockchain Stamping