• Proof of Existence
  • About the Service
  • Protocol Summary
  • Costs

Proof of Existence

Proof of Existence is a method of verifying and recording that specific data existed at a certain time. To establish proof, a timestamp and signature linked to the entity are needed to demonstrate its creation at a particular time. Blockchain technology provides a convenient solution for this purpose, as proof is stored on a public ledger that is transparent, unalterable, and permanent.

Common Use Cases:
  • Proof of ownership.
    The owner of the data can confirm ownership without revealing the actual data.
  • Data timestamping.
    You can prove the existence of specific data at a particular time without relying on a central authority.
  • Data Integrity Checking.
    If there is even the slightest change in the document (even a single bit), it will result in a different file hash. By creating a stamp of your data and verifying it later, you can ensure that the data has not been altered.

About the Service

This service provides a straightforward implementation of the Proof of Existence concept on the Gridcoin blockchain. You can securely and anonymously store proof of the existence of any of your documents (e.g. images, videos, documents, binaries) in the decentralized ledger without revealing the actual content of the document.

We do not store any of your data (with the exception of the document's hash). Your documents are not uploaded to our database or stored on the blockchain, and they never leave your device.The document's SHA-256 hash is calculated client-side, in your browser, to ensure the security of your data.

We also prioritize privacy and do not use any tracking pixels. The only exception is Plausible , which is considered a privacy-friendly alternative to Google Analytics.

Protocol Summary

The data is stamped on the Gridcoin blockchain by embedding the sha256 hash of the data in a transaction. This is achieved through the use of an OP_RETURN script opcode, which creates an unspendable output in the transaction that encodes the hash.

A typical transaction may contain one or two hashes, such as:


or like that:


The key difference between the two transactions is that the second one includes two hashes, while the first one only has one. The OP_RETURN script is capable of accommodating two sha256 hashes, allowing for more than one record to be stored in a single transaction. This not only helps to save on fees but also makes it more efficient.

Let's take a closer look at what makes up the transaction:

6a46 - This is the hexadecimal representation of the OP_RETURN script

5ea1ed - A unique sequence of characters that helps identify the stamp transaction and process it. This is known as a “hex word” and reads as “Sealed”.

000001 - The protocol version. The current version at the time of writing is 0.0.1, using semantic versioning. All future versions shall support legacy protocols.

5bbbbbee48b735693478140de1b7f09fe0acddc0c7bce87f8665074efe53410f - The first sha256 hash.

7158380aca149fa8422fb1274a69155303d4aaa76bf67defe0bb31628293afd2 - The second sha256 hash (if present).


As of the time of writing, the cost of a stamp transaction is low, consisting of a small burned amount (0.00000001 grc or one Halford) and a transaction fee (approximately 0.05 grc). The average cost is around 0.06 grc per proof.

The service is currently offered for free, but this may change in the future if demand is high. Currently, the low cost and level of donations suggest that the service will remain free for the foreseeable future.

Stamp service wallet balance: grc
Address: SHpqN8xEjy2HHTnAGfgJjwFThuqzLbBs6i

Made with by @gridcat