An export, file, exact text, or snapshot from any system—even one Summit cannot see.
Σ · No-access proof primitive
Prove the bytes.
Reveal nothing.
Turn a file, export, receipt, message, or system output into a portable witness without an API key, admin role, integration, or upload.
proof-mode/witness@1Σ
SHA-256 / LOCALCONTENT INCLUDED: FALSEWeb Crypto computes SHA-256 locally. Only the digest and limited metadata become portable.
Recompute the digest against the same bytes. Match means identical; mismatch means changed.
Local witness lab
One artifact.
One durable fingerprint.
This tool does not upload, store, or inspect your source content. A digest can still identify known or guessable content, so never hash passwords, short secrets, or low-entropy values.
LOCAL / PRIVATEYour file or text is hashed in this browser. It is never sent to Summit.
OR
Nothing leaves this browser.
Exact proof boundary
What a witness
can—and cannot—say.
The bytes compared now are identical to the bytes hashed at capture time, assuming SHA-256 remains collision resistant and the witness record is authentic.
Who authored the artifact; whether its claims are true; whether the export is complete; or what an inaccessible system did before or after capture.
A signed commitment that an authenticated person attached the witness to a specific review path at a recorded time—without sending the artifact to the signer.
A universal evidence edge
Works where integrations stop.
Use the open witness JSON today. Add native capture or third-party attestation later without changing the human proof surface.
Read the builder contract