Bitcoin Proof of Existence
Prove that a file existed before a point in time without putting the private file on a public blockchain.
The file stays private
A hashing function converts a file into a short fingerprint. A timestamping tool can commit that fingerprint into a larger Merkle structure anchored to Bitcoin. The original document does not need to be uploaded to the blockchain.
What the proof can establish
Given the original file and a valid proof, a verifier can independently check that the matching hash was committed before the Bitcoin block containing the anchor. This supports evidence of existence, not proof that a claim inside the document is true.
Why batching matters
Many hashes can be combined into one Merkle root. A single Bitcoin commitment can therefore anchor a large number of timestamp proofs without one on-chain transaction per document.
Use a reviewed implementation
OpenTimestamps is one public protocol for this pattern. Back up both the original file and its proof, understand the verification model, and obtain legal advice before relying on a timestamp in a formal dispute.