A client disputes which version you delivered, or when. HashStamp seals your file's fingerprint into a tamper-evident chain at a stated time — a receipt anyone can verify. Pair it with your email or upload record to settle exactly which file, and when.
Works with anything you can upload: contracts, designs, manuscripts, code, invoices, deliverables. If it's a file, you can stamp it.
Drop in a file. It's hashed in your browser — the file itself never leaves your device. Only its SHA-256 fingerprint (and any public label you choose to add) is sent. You get a real, verifiable timestamp on the ZKNOT chain.
You don't have to take our word for it — and neither does your client. The proof checks itself.
Drop in the deliverable — a PDF, a design, a contract, a zip. We never store the file itself, only its cryptographic fingerprint.
You get a timestamped, tamper-evident proof: the exact file fingerprint, sealed at a stated time, recorded in a hash-linked chain.
Hand your client a link. They confirm the file and the date themselves — no account, no login, no calling you. The math does the vouching.
What a HashStamp proves
That this exact file — identified by its SHA-256 fingerprint — existed at the stated time, signed by HashStamp's service key and hash-linked into a tamper-evident chain. Anyone can check it without trusting you.
What it does not prove
Who created or sent the file, that a recipient received it, or that the time is independently anchored — the timestamp is provided by the HashStamp service, not an external authority. Pair a stamp with your delivery record (an email, upload, or shared link) to show which version you delivered.
Anything you control, a client can argue you faked. The point of proof is that it doesn't depend on you.
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No. We compute a one-way fingerprint (a SHA-256 hash) of your file and store only that. We never see or keep the file's contents — we couldn't reconstruct it if we tried.
Hashstamp gives strong, independently verifiable evidence of when a specific file existed and that it hasn't changed since. Whether that's decisive in a given dispute depends on the situation — but "here's cryptographic proof, verify it yourself" is a much stronger position than "trust me, I sent it on time."
Not on its own — and we're careful not to claim it does. A stamp proves that this exact file existed and was sealed at a specific time, and hasn't changed since. What that kills is the two moves a client can make: "that's not the file we agreed on" and "you backdated it." Pair the stamp with your own send record — the email, the shared link, the upload — and it stands on cryptographic proof instead of your word against theirs.
They see a verification page: the file fingerprint, the timestamp, and a confirmation that it's intact. They never see your account or anything else you've stamped. One link, one proof. A stamp shows that this exact file was recorded at that time — it doesn't assert who created or uploaded it.
A tamper-evident, hash-linked ledger — the same evidence infrastructure behind ZKNOT. You don't need to understand any of that. You upload a file; you get a proof.