How to Prove a Prediction Was Made Before the Event (with OpenTimestamps)

Short summary

OpenTimestamps uses the Bitcoin blockchain as a tamper-evident clock to prove a document existed at a specific time without revealing its contents. The process hashes a file locally, submits the hash to a calendar server, aggregates it into a Merkle tree with other users' hashes, and anchors the root in a Bitcoin transaction. This enables sealed-then-scored forecasting where predictions cannot be retroactively edited.

• •OpenTimestamps anchors document hashes in Bitcoin blocks to prove when a prediction was made
• •Only the SHA-256 hash is submitted — document content never leaves your machine
• •A .ots proof file contains the Merkle path linking your hash to a specific Bitcoin block timestamp

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