Proof Anchored on chain

Standard proofBSV mainnet
Anchored at
2026-05-02T02:04:16Z UTC
Proof
Standard proof — file never left your device
Submitter’s label
sample.png
Provided by the submitter; not checked by Satsignal.
Proof ID
bfe1297b68484179

View on Bitcoin SV chain →

Includes the bundle, a printable PDF proof, and a verify guide. Keep alongside the original file.

Include the original file in this package (optional)

Pick the file you anchored. Your browser will re-hash it locally and compare against the anchored fingerprint; the file’s bytes never leave this page. If it matches, it will be bundled into original/ inside the ZIP so recipients have everything in one place.

Keep these two together

your original fileYou keep this — re-hashed at verify time
satsignal-proof.mbntbundle — the portable proof file a verifier uses to re-check the proof

Verifying later needs both: your original file and the bundle. The proof commits to the file’s fingerprint, not its bytes — we never had them.

In plain terms. This is tamper-evident proof that whoever anchored it held this file’s fingerprint (its SHA-256) by 2026-05-02T02:04:16Z UTC, recorded on the public BSV chain. Anyone can re-check it without trusting Satsignal — it does not establish authorship, or that the event the file describes actually happened. The full breakdown is below.

Standard proof — file never left your device. Your file was NOT uploaded. Only its SHA-256 hash, file size, and any label you typed were transmitted.

What this proof establishes — and what it does not.
A valid proof establishes the file existed in this exact form at the time of the on-chain transaction. It does not prove:
Technical proof detail — hashes, on-chain commitment, size
File SHA-256 file fingerprint
139eb4599dace99757b1d7a441abc4981d629951aaa91f23089a38f8240ae17d
File size
1,920bytes
Filename label
sample.png
Anchored at (UTC)
2026-05-02T02:04:16ZUTC
Transaction on-chain record
031e6b1e44a0edab62d1ea75f9a898a994e86f11c87be0779fa12cbec7bd4538
On-chain commitment cryptographic anchor
6e9091e901a76d463e7282383d91bb5ecbec447a (sha256 of canonical proof doc, first 20 bytes)

Proofs anchored

Three orthogonal proofs about your file are committed in a single on-chain anchor. Use whichever the situation calls for.

Byte-exact
139eb4599dace99757b1d7a441abc4981d629951aaa91f23089a38f8240ae17d
SHA-256 of the file as uploaded. A single-byte change anywhere produces a different hash.
Content-canonical
2a61b3da3e704fd82f73248130c69068f3ec78a8dd31912a29923f24f08eaba9
Scheme: image pixel data (metadata stripped). Resilient to non-meaningful changes (resave, metadata churn, line-ending drift).
Per-section commitment
779e410d002ab5a5bf8870a8558fd8ae51c58333efd51c6de2f4dfab8a71445e
Scheme: per-tile · 2 leaves. Lets a holder later prove a single chunk was part of this file without revealing the rest.
Other download options
Bundle only (.mbnt)

Create another proof →

How to verify this proof yourself (manual recipe)
In one sentence: re-fetch the transaction from any BSV block explorer, recompute the canonical proof's hash, and check that your file's SHA-256 matches the one inside — if all three match, the proof is intact and the original file is the one anchored. The verifier at /verify does this for you in your browser in one click.

For an audit trail or scripting, here are the manual steps anyone can run with sha256sum:

  1. Re-fetch the on-chain transaction: https://whatsonchain.com/tx/031e6b1e44a0edab62d1ea75f9a898a994e86f11c87be0779fa12cbec7bd4538 — confirm an OP_RETURN output starting with the bytes MBNT.
  2. Decode the OP_RETURN payload: bytes 8–27 are the doc_hash (sha256 of the canonical proof doc, truncated to 20 bytes; bytes 0–3 are MBNT, 4 the version, 5 the subtype, 6–7 the TLV length). It must match 6e9091e901a76d463e7282383d91bb5ecbec447a.
  3. Hash the included canonical.json from the .mbnt bundle directly — the bundle stores the exact bytes that were hashed on-chain, so do not re-canonicalize: sha256sum canonical.json | cut -c1-40. The first 40 hex chars must equal 6e9091e901a76d463e7282383d91bb5ecbec447a. (If you instead re-canonicalize to defend against a tampered stored copy, you MUST use SCJ-v1 — code-point key sort, NFC, floats forbidden — not RFC 8785 / a generic JCS library: the product uses three non-interchangeable JSON canonicalizers. See the MBNT spec §5.)
  4. Sha256 the original file — must equal the File SHA-256 above. The bundle does not contain the bytes; you kept them.
What we kept: this bundle (downloadable above) and one access-log line for this request. What we did NOT keep: the original file — the bytes never reached us. The on-chain anchor is permanent.

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