Knowledge Base

Overview

This r/Bitcoin discussion thread explains how OpenTimestamps (created by Peter Todd) provides a scalable, trustless way to prove that data existed at a given point in time using the Bitcoin blockchain. The core idea is that only the SHA-256 hash of a document is submitted, never the document itself, so timestamping is private and cheap. Calendar servers batch many submitted hashes into a single Merkle tree and commit only the tree root into one Bitcoin transaction, letting a single on-chain commitment timestamp an unlimited number of documents.

Key points

• A user hashes their file locally (SHA-256) and submits only that digest to one or more public calendar servers; the original data never leaves the user’s machine.
• Calendar servers aggregate many submitted digests into a Merkle tree and commit the single Merkle root into a Bitcoin transaction, so on-chain cost is amortized across all submissions in that batch.
• The user receives an .ots proof file containing the ordered commitment operations (byte append/prepend, SHA-256 steps) that form the Merkle path from their document hash up to the root recorded in a Bitcoin block.
• Verification is offline and trustless: walking the .ots operations must reproduce a Merkle root that appears in a confirmed Bitcoin block, whose timestamp establishes the data existed at or before that block.
• Because the proof is self-contained and checkable against Bitcoin, the calendar server does not need to be trusted after confirmation, and the scheme is free, decentralized, and blockchain-agnostic in principle.

Relevance to Truestamp

OpenTimestamps is a direct conceptual predecessor to Truestamp’s model: both hash data, aggregate many items into a Merkle tree, and record a root on a public chain. Truestamp similarly uses inclusion proofs and public-blockchain commitment, including Bitcoin, while adding submission-window framing and richer signed proof bundles.

Citations

1. How Does OpenTimestamps Work (r/Bitcoin discussion). Reddit r/Bitcoin community thread on the OpenTimestamps protocol (Peter Todd); source page not directly fetchable, summarized from knowledge of OpenTimestamps.