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Files extension

Proof the file existed today, written on Bitcoin

Files computes the SHA-256 fingerprint of the content and anchors it to the Bitcoin blockchain through OpenTimestamps. The result is an immutable proof that the file, as it is, existed at that moment — verifiable by anyone, even without Kamzan.

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What it proves, and what it does not

The timestamp proves two things: that the content existed at that date and that it has not changed since. Verification recomputes today’s fingerprint of the file and compares it with the anchored one: “unchanged since anchoring” or “warning, modified afterwards” — even if the change was restoring a previous version. It is not a Qualified Timestamp under the eIDAS Regulation: it is a cryptographic anchor on a public blockchain, and Files states so in the dialog before requesting it. For full legal value there are compliant preservation and signature.

How it works

  1. Request the timestamp

    Right-click → Blockchain timestamp. Files computes the SHA-256 hash of the content, sends it to the OpenTimestamps network and saves a snapshot of the file state. If you like, an email tells you when it is confirmed.

  2. Wait for the Bitcoin block

    Confirmation on the blockchain takes about one to two hours. Meanwhile the file carries the “pending” badge; when the proof is inside a block it becomes “confirmed”, with the block height in the details.

  3. Verify, today or in ten years

    One click recomputes the fingerprint and compares it. Download the .ots proof and verify it with any OpenTimestamps client: the dialog explains how, because the proof must not depend on us.

No need to trust us: anyone can verify the proof.

What you can do

  • Portable proof

    The .ots file is the OpenTimestamps standard: it verifies with public tools, with no Kamzan account. If one day the file leaves Files, the proof leaves with it.

  • Integrity at a glance

    Badge on the file, status in the details, verification result in plain words. If someone overwrites the file or restores a previous version, verification says so.

  • Monthly quota per company

    Timestamps are counted per month and per tenant — a hundred by default, configurable in the extension — so a runaway automation does not generate surprise costs.

  • “Timestamp” collection

    All timestamped files in one list, with the state of each: pending, confirmed, intact or modified.

  • In the feed and the log

    Request and confirmation appear among the file’s activities — “requested the timestamp”, “confirmed” — and in the audit log.

Frequently asked questions

Does it have legal value?

It is a technical proof of existence and integrity, robust and third-party verifiable, but not an eIDAS Qualified Timestamp: it does not enjoy that one’s legal presumption. When full value is needed, use compliant preservation or signature with kSign, and the blockchain timestamp as additional evidence.

Why does it take one or two hours?

Because the proof becomes final when the fingerprint enters a Bitcoin block, and blocks arrive roughly every ten minutes; OpenTimestamps batches requests before writing them. Files checks periodically and updates the status on its own.

Does the file content end up on the blockchain?

No: only the SHA-256 fingerprint, from which the content cannot be reconstructed. The file stays in Files, encrypted like all the others.

The other Files features

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