What a proof shows, and what it does not.

What it proves

What does a Verifyum proof show?

That this exact file existed no later than the block time of its Solana transaction, and has not changed since. The block time shows when the commitment entered the block.

It does not show when the file was created, who made it, who owns it, or that anything in it is true. A proof is evidence that a file existed, unaltered, at a moment. It is nothing more than that.

Your file

Is my file uploaded?

No. Your browser, or the command-line and MCP tools, hash the file on your device and send only a commitment derived from that hash and a random nonce. We never receive the file, its name, its hash or the nonce, and the commitment cannot be reversed into any of them. The Privacy page says exactly what we do receive.

Accounts

Why is there no account?

Because nothing about a proof needs to know who you are. A commitment is all the service ever handles. To prevent abuse, creating proofs is limited per address, per hour and per day, and the address is kept only as a keyed hash that is never stored with the proof.

The nonce

What is the nonce, and why must I keep it?

The nonce is 32 random bytes generated on your device and kept in the private draft. It blinds the commitment, so the public record cannot be matched against a file someone else already holds. It is also the only thing that lets you show, later, that your file is the one the proof commits to.

We never receive it. If you lose the draft, nobody can show the link between your file and the proof, and that includes us. Keep the draft with the original file.

Durability

What happens if Verifyum disappears?

The proof does not depend on us staying online. Its Solana transaction is public and stays readable without us. The checkpoints that contain it are also held by independent witnesses run by other operators: anchored in Bitcoin through OpenTimestamps, timestamped by a qualified EU trust service, logged in Certificate Transparency and Sigsum, and archived at GitHub, the Internet Archive and Software Heritage.

A receipt written by the command-line client after the proof is finalized carries the signed proof record, both Merkle paths and the service key registry, so it can be checked with no network at all. From the website, keep the draft and save the public proof link.

Solana and witnesses

Why Solana, and why the witnesses?

Solana confirms the commitment within seconds and gives a public record anyone can read. The witnesses add durability and independence, through different operators in different jurisdictions. They are not all equal: Bitcoin is slow but the most durable record available, and the qualified EU timestamp is the one that carries a legal presumption. A pending or missing witness never invalidates the Solana proof. The Witnesses page names each one, what it contributes and where it stops.

Legal standing

Is this legal evidence?

Verifyum produces technical evidence. One part of it carries a statutory presumption: the daily checkpoint is timestamped by a qualified timestamping service listed on an EU Trusted List, so under eIDAS Article 41(2) the time and integrity of that checkpoint's root are presumed correct across the EEA, and the burden falls on whoever disputes it.

That presumption covers the root only. The step from the root to your file is shown by the Merkle path like any other technical fact, so a Verifyum proof is never itself a qualified timestamp. How any evidence is weighed is for whoever decides the matter.

Price

What does it cost?

Public use is currently free, and AI SENSE AS pays the Solana network fee. That is a current service policy, not a permanent pricing guarantee.

Checking it yourself

How do I check a proof with no Verifyum software?

The draft holds the private manifest, which is the file's hash and size and the nonce, and the commitment. The commitment can be reproduced from that file alone, with any SHA-256 and any RFC 8785 implementation:

commitment = 'sha256:' + hex(SHA-256('verifyum:commitment:v2' + LF + JCS(manifest)))

LF is one newline byte, and JCS is RFC 8785 canonical JSON. Hash your file to confirm it matches the manifest, then compute the commitment. The memo of the proof's Solana transaction reads verifyum:v2:id=<proof id>;alg=sha256;commitment=<digest>, where the digest is your commitment without its sha256: prefix. Drafts also carry this recipe inside them, as derivation.

The verification code is public, in six independently written implementations that agree byte for byte on a shared set of vectors.