How to prove you signed without sharing the contract

Why forwarding the contract shares too much

When a lender, a landlord or a new client asks whether an agreement exists, the usual answer is to forward the signed PDF. That hands over everything in it: prices, salaries, payment terms, and the names and signatures of everyone involved. Often the person asking needs one fact: that the agreement exists, who signed it and when it was completed.

Attest's Share proof gives them that fact and nothing else. Of the 21 e-signature services we compared in October 2026, Attest and 20 others, Attest was the only one offering zero-knowledge proofs.

What a zero-knowledge proof is

A zero-knowledge proof is a piece of cryptography that convinces someone a statement is true without showing them the information behind it. An everyday comparison: you can prove you know the combination of a lock by opening it in front of someone, without telling them the numbers.

On Attest, the statement is about a completed agreement: that your email address signed it, or that your address and a named co-signer's address both signed it, and the date it was completed. The proof is checked against an anchored record of completed agreements, so the recipient knows the statement is true without seeing the agreement.

What the recipient sees, and what stays private

The recipient sees	Never shown
Your email address	The document and its terms
The co-signer's email address, if you choose to name one	The document's title
The completion date, as a calendar day (UTC)	Any other signer
That the proof is valid, and where its record is anchored

A proof names email addresses, not company names. If Mary Ruiz (user@domain.com) proves an agreement with a client, the recipient sees her address, the client signer's address, the date, and that the proof is valid and where its record is anchored.

The proof doesn't say what the agreement is about, by design. You tell the recipient what it is, and the proof confirms that the named people signed an agreement completed on that date. A proof fits when the person asking needs the fact. If they need to read the terms, share the document itself.

Who you might show it to

A bank or lender, a landlord, an investor, a new employer or a business partner often needs only to know that an agreement exists and who signed it. Proving an agreement to a bank, landlord, investor or new employer covers what each one asks and which proof fits; for an auditor, see proving when an agreement was signed, and for a business partner, proving a partnership is in place. In each case the prices, salary, scope and other terms stay between the parties.

How to create and share a proof

1. Sign in at attest.datahubz.com and open the completed document in your dashboard.
2. Choose Share proof on that document.
3. Choose what to prove: that you signed it, or that you and another signer signed it. If you name another signer, pick which one.
4. Create the proof. The proof Attest makes for you appears in the list shortly after the agreement completes, marked "Made for you when it completed".
5. Copy the proof's link and send it, or give the recipient its proof ID, which starts with azk_.
6. The recipient opens the link, or enters the proof ID at attest.datahubz.com/verify.

Each proof is submitted to zkVerify for independent verification, and the proof page shows that it is being verified until zkVerify finalizes it. You can make up to 10 proofs per party per agreement, and each one can be checked any number of times. Proofs are made by signers, so if you send a document and will need a proof about it, add yourself as a signer when you send. How to share proof that you signed covers every option, and the tutorial Verify a signed document, and share proof shows each step on the real app.

How the recipient checks it

Checking is free and needs no account. The verify page shows the statement, whether the proof is valid, where its record is anchored and its zkVerify status.

The checks don't rest on Attest's word:

• zkVerify is the network that independently verifies every zero-knowledge proof Attest makes.
• The record of completed agreements that each proof is checked against is anchored on Horizen, a public blockchain, and only fingerprints go on chain, never document content, titles or emails.
• Attest's open-source verifier checks zero-knowledge proofs too: the proof's page offers its evidence file, which the verifier checks on the recipient's device. Each party shares their proof from that page. The signed copy carries no proofs, because a proof names its party's email address and the signed copy names signers only by name.

For the technically minded: proofs are Groth16 proofs on the BN254 curve, made against the anchored commitment root of its agreement's tree (65,536 agreements each). Attest generates them on its servers, and a proof reveals only its statement.

Keep the agreement itself private

The document stays private either way. Every document sent through Attest is end-to-end encrypted in the sender's browser, and Attest stores it only as ciphertext it can't read.

The record of who signed is a separate setting. An agreement's certificate is public by default, and a public certificate shows anyone with its link, ID, stamp code or the document's fingerprint the title, the file name, the verification code, the fingerprints of the document, the signed copy and the signed state, each signer's name and signing time, the blockchain anchor and each signature's evidence. It never shows the document, and it shows signers' email addresses only to the parties. The sender can make it private when sending, or at any time later with Make private. Anyone who then looks the agreement up is told it exists and is private, and the parties share zero-knowledge proofs instead.

What it costs

Share proof is on every plan, Free included. Proofs come with the document and use none of your documents or records. The people who sign never pay, and checking a proof is free for anyone. Your first 2 documents are free, in total, and the Signing plan is $5 a month for 20 documents.