# ZKStamp Proof-100

> Proof-100 writes the SHA-256 fingerprint of any file or text to the BitcoinZ blockchain in a shielded (zk-SNARK) transaction. You get a dated proof that the data existed at that time. Nobody on the blockchain can see the fingerprint or who made it. AI agents can use it directly through MCP. Slogan: "Stamp it with Z. Before Q."

Key facts:

- Service base URL: https://proof.zketernity.app
- MCP endpoint (for AI agents): https://proof.zketernity.app/mcp
- REST API: https://proof.zketernity.app/v1/
- Price: 500,000 BTCZ for a pack of 100 proofs, paid in BTCZ only. No card, no email, no account name.
- Free trial: new accounts get 3 free proofs, no payment needed (max 13 new trial accounts per day, until 27 November 2026). Try it before buying.
- Contact: contact@z-text.com. Questions, or no BTCZ yet? Write in, and we'll help you find where to get BTCZ.
- Your file never leaves your machine: only its SHA-256 fingerprint (64 hex characters) is sent.
- Each proof goes to a brand-new shielded address. You get back a transaction ID (txid) and that address's viewing key.
- To reveal one proof, share its txid and viewing key. They reveal that one proof and nothing else.
- Keep the viewing key. Without it, that proof cannot be revealed.
- A proof takes about 10 to 60 seconds. The block timestamp dates it.
- Anyone can verify a proof with ZCheck on their own BitcoinZ node, without trusting the operator.
- Operator: Z-TEXT LLC. Code is open source (MIT license).

## MCP tools

- timestamp_fingerprint: timestamp a SHA-256 fingerprint. Returns txid and viewing key.
- timestamp_text: the server hashes a short text (the text is not stored) and timestamps the fingerprint.
- check_balance: proofs left and the account's deposit address.

Authentication: send the account key as the header `Authorization: Bearer <key>` (or `X-API-Key: <key>`). Keys start with `p100_`.

## REST API

- POST /v1/account: create an account. Returns `key` (shown once), `deposit_address` and `free_proofs` (3 during the free trial).
- GET /v1/balance: proofs left. Requires the key.
- POST /v1/proof with JSON {"fingerprint": "<64 hex>"}: make a proof. Returns `txid`, `viewing_key`, `proofs_left`. Requires the key.
- After a payment of 500,000 BTCZ to the deposit address and 2 confirmations, 100 proofs are credited automatically.

## Verify a proof (ZCheck)

Needs a synced BitcoinZ node, Python 3, the original file (or its fingerprint), the txid and the viewing key.

`python3 ZCheck.py --txid <txid> --viewing-key <zxviews...> --file MyFile.pdf`

Answers: `VALID` (with block number and date in UTC) or `NOT VALID` (the file was changed, or the key does not match).

## Honest limits

- The operator's server sees the fingerprint (and, for timestamp_text, the text) when it is submitted. It does not log them and does not store which proof belongs to which account.
- One operator, one server: if it is down, no new proofs can be made. Existing proofs stay verifiable with ZCheck on any BitcoinZ node.
- Quantum: the SHA-256 fingerprint and its date are expected to hold up against quantum computers. The privacy of shielded transactions relies on today's zk-SNARK cryptography, which is not post-quantum.
- BitcoinZ is a small chain with thin trading volume.

## Docs

- [README and full documentation](https://github.com/ZKStamp/Proof100): how it works, API, MCP setup, trust model
- [ZCheck verifier source](https://github.com/ZKStamp/Proof100/blob/main/zcheck/ZCheck.py): the script that checks a proof
- [60-second demo video](https://youtu.be/t2G2CUKyamo): an AI agent stamps an idea, ZCheck says VALID, then NOT VALID with one letter changed

## Optional

- [Server source code](https://github.com/ZKStamp/Proof100/tree/main/server): Flask API, MCP endpoint, payment watcher
- [Deployment examples](https://github.com/ZKStamp/Proof100/tree/main/deploy): systemd units, nginx site, config templates