# Proovik > Proovik is a proof-of-existence and supply-chain traceability service anchored on the Kaspa blockchain. It issues non-qualified electronic time stamps (Art. 3(16) of Regulation (EU) 910/2014, eIDAS) that prove a document already existed at a given date and time, without the document ever leaving the user's device, and records EPCIS 2.0 traceability events for products. Every proof is verifiable by anyone, offline, without Proovik, using the public PVK-PROOF/1 specification. Key facts: - What is anchored: only the SHA-256 hash of the file (32 bytes), written in the payload of a Kaspa transaction. The file itself is never uploaded; the hash is computed in the browser or by the API client. - What a proof shows: that a document with a given SHA-256 existed no later than the timestamp of the Kaspa block that includes the transaction, a timestamp covered by that block's proof of work. It does not prove authorship, truth of content, or that the document did not exist earlier. - Legal nature (EU): non-qualified electronic time stamp. It cannot be denied legal effect solely for being electronic (Art. 41(1) eIDAS), but it does not carry the presumption of accuracy reserved to qualified time stamps (Art. 41(2)). Proovik is not a notary and not a qualified trust service provider. - Timing: Kaspa produces about ten blocks per second; a seal is normally confirmed within seconds. The certificate reports the block timestamp (UTC) as the proven date and time. Certifications can be reported as pending until the transaction is confirmed. - Verification: four independent checks (document hash present in the transaction payload; transaction committed in the block via the KIP-15 acceptedIdMerkleRoot witness; block header hash; kHeavyHash proof of work against the header's target). A dependency-free Python reference verifier is downloadable from the verification page. The certificate PDF embeds the complete proof, so it stays verifiable even if Proovik disappears. - Traceability: EPCIS 2.0 events (Object, Aggregation, Transaction, Transformation, Association) validated against the GS1 JSON schema, chained by hash, signed per actor and anchored on Kaspa; GS1 Digital Link, GTIN / SGTIN / lot lookup; consumer verification by QR. - Languages: 23 (Spanish is the site default; reviewed languages are es, en, de, fr, pt, it). - Pricing: 3 free certifications, no account and no card; paid plans in EUR for professionals, API integrators and traceability. See the pricing page for current figures. ## Core pages - [Document certification (proof of existence and prior date)](https://proovik.com/en/certification): what is certified, privacy model, legal value, FAQ. - [How to verify a Proovik proof without trusting Proovik, PVK-PROOF/1](https://proovik.com/en/verify): online verifier, step-by-step specification with real values, what the proof does and does not assert. - [Product traceability (EPCIS 2.0 on Kaspa)](https://proovik.com/en/traceability): hash-chained events, QR verification, protocol. - [Pricing](https://proovik.com/en/pricing) - [Certify a document now](https://proovik.com/en/certify): free, browser-side hashing, no account. - [How to prove that a document existed on a date](https://proovik.com/en/how-to-prove-a-document-existed-on-a-date): the five methods compared (notary, qualified eIDAS time stamp, registered mail, public registry, proof-of-work blockchain seal), what the law says, what a seal does not prove. - [Blockchain timestamp: what it is and how it works](https://proovik.com/en/blockchain-timestamp): definition, difference from a qualified time stamp and a notary, honest comparison with OpenTimestamps and qualified TSAs. - [EPCIS 2.0 traceability](https://proovik.com/en/epcis-traceability): the five event types with a valid EPCIS 2.0 JSON-LD example, GS1 Digital Link, what anchoring on Kaspa adds, regulated sectors (EUDR, battery passport, FMD). - [How it works](https://proovik.com/en/how-it-works) · [Benefits](https://proovik.com/en/benefits) · [Use cases](https://proovik.com/en/use-cases) · [FAQ](https://proovik.com/en/faq) ## API - [API overview](https://proovik.com/en/api) and [API reference](https://proovik.com/api-docs). REST over HTTPS, JSON bodies and responses. Authenticated calls send `Authorization: Bearer `. Without a key, `POST /api/certify` applies a small free quota per device and IP. - `POST /api/certify` — body `{ "hash": "", "description": "optional", "email": "optional" }`. Responds 200 when the seal is confirmed, 202 when the transaction exists but is still pending (poll `GET /api/certify/reconfirm?hash=`), 429 when the free quota is exhausted. Returns the Kaspa txid, block timestamp and explorer URL. - `GET /api/verify?hash=` — has this hash been certified, when and in which transaction. - `GET /api/certificate?hash=&lang=` — certificate PDF with the embedded PVK-PROOF/1 proof. - `GET /api/certify/proof?hash=` — proof package as JSON (API key required). - `POST /api/verify/proof` — verify a proof package against a document hash supplied by the caller; the hash is never taken from the package. `GET /api/verify/proof/{txid}` — verify by transaction id. - `POST /api/trace/batch`, `POST /api/trace/event`, `GET /api/trace/batch/{batch_id}`, `GET /api/trace/event/{event_id}`, `GET /api/trace/verify/{batch_id}`, `GET /api/trace/search?gtin=|sgtin=|lot=|product=`, `GET /api/trace/batch/{batch_id}/proof`, `GET /api/trace/event/{event_id}/proof`, `GET /api/trace/batch/{batch_id}/qr` — EPCIS 2.0 traceability (API key required for writes). - Public consumer verification of a batch: `https://proovik.com/verify/{batch_id}`. ## Guides and articles - [How to give a digital contract a provable date](https://proovik.com/en/articles/how-to-certify-a-digital-contract-date-in-2024) - [Proof of existence with a zero-knowledge architecture on Kaspa](https://proovik.com/en/articles/digital-sovereignty-proof-of-existence-kaspa) - [Protect your intellectual property without patents](https://proovik.com/en/articles/how-to-protect-your-intellectual-property-without-patents) - [Protect your NDA or supplier contract](https://proovik.com/en/articles/how-to-protect-your-nda-or-contract-with-suppliers) - [Immutable audit logs: syslog to blockchain](https://proovik.com/en/articles/immutable-audit-logs-syslog-to-blockchain-with-proovik) - [Software integrity: verifiable anti-tampering](https://proovik.com/en/articles/software-integrity-testing-blockchain-verifiable-anti-tampering) - [Food traceability and regulatory compliance](https://proovik.com/en/articles/food-traceability-compliance-regulations-blockchain) - [Pharmaceutical cold-chain traceability](https://proovik.com/en/articles/pharmaceutical-traceability-verifiable-cold-chain-blockchain) - [All articles](https://proovik.com/en/articles) ## Español - [Certificación de documentos (prueba de existencia y anterioridad)](https://proovik.com/es/certificacion) - [Cómo verificar una prueba Proovik sin fiarse de Proovik, PVK-PROOF/1](https://proovik.com/es/verificar) - [Trazabilidad de productos (EPCIS 2.0 sobre Kaspa)](https://proovik.com/es/trazabilidad) - [Cómo demostrar que un documento existía en una fecha](https://proovik.com/es/como-demostrar-que-un-documento-existia-en-una-fecha) · [Sello de tiempo blockchain](https://proovik.com/es/sello-de-tiempo-blockchain) · [Trazabilidad EPCIS 2.0](https://proovik.com/es/trazabilidad-epcis) - [Precios](https://proovik.com/es/precios) · [Certificar ahora](https://proovik.com/es/certificar) · [Cómo funciona](https://proovik.com/es/como-funciona) · [Preguntas frecuentes](https://proovik.com/es/preguntas-frecuentes) · [Artículos](https://proovik.com/es/articulos) ## Optional - [Privacy policy](https://proovik.com/en/privacy-policy) · [Terms of use](https://proovik.com/en/terms-of-use) - [Contact](https://proovik.com/en/contact) - Kaspa network: https://kaspa.org · KIP-15 (acceptedIdMerkleRoot chaining) · Regulation (EU) 910/2014: https://eur-lex.europa.eu/eli/reg/2014/910/oj