Data protection
Privacy Policy
What we process, why, who else receives it and what you can demand from us.
Last updated: 5 October 2026
Who is responsible
Cristian Cascante Portabella, tax ID 38846956W, Plaça d'Ibèria 1, 08014 Barcelona (Spain), is the controller of the personal data collected through sellat.app. Sellat is his trading name.
For anything about your data, including exercising your rights: [email protected].
If you are a customer of a shop that uses Sellat
Some online shops connect their shop to Sellat to keep proof of their orders. In that case, the shop is the controller of your data, and Sellat processes the record of your order on its behalf, as a processor: amounts, lines, dates, the terms you accepted, your customer identifier in the shop and a fingerprint of your email address, never the address itself. Only if the shop turns it on, also the IP address from which you accepted the terms or a full copy of the order, which includes your name and addresses.
That data is processed so that the shop can prove the order, and Sellat keeps it for as long as the shop keeps its account. To exercise your rights over it, contact the shop; if you write to us at [email protected], we will pass your request on.
What we process and why
Each purpose, with the legal basis that allows it. Your email address is needed to send you the certificate and to run your account: without it we cannot provide the service. The other data are processed only if you use the corresponding feature.
| Purpose | Data | Legal basis |
|---|---|---|
| Creating, keeping and verifying your proofs | SHA-256 fingerprint, file name, type and size, date. Signed in, the file is not uploaded; without an account it is used to compute the fingerprint and not kept | Performance of the contract |
| Sending you the certificate and the verification package | Email address | Performance of the contract |
| Your account and access to it | Email and, if you sign in with Google or Microsoft, your name (and, with Google, your profile picture) | Performance of the contract |
| Organising our communications about Sellat according to how you use the service | Email, name, language and usage tags: whether you have an account, whether you have protected a file and whether you have used the free or a paid qualified timestamp. Never your files, their fingerprints or their names | Legitimate interest. We send you no advertising without your prior consent, and you can object by writing to [email protected] |
| Sending you Sellat news, only if you ask for it from your account | Email, name and language | Consent, which you can withdraw at any time from your account or with the unsubscribe link in every email. It is independent of your account, your proofs and your purchases |
| Custody of the original file (optional) | The file you deposit | Performance of the contract, at your request |
| Issuing a qualified timestamp | The fingerprint and the order identifier | Performance of the contract |
| Connecting an AI assistant (ChatGPT, Claude) to your account, only if you do it | The fingerprints, file names, dates and status of your proofs, and the account details the assistant looks up (plan, seals, limits). Never the files held in custody | Performance of the contract, at your request. You can disconnect the assistant at any time from your dashboard |
| Payments and subscription | Email, Stripe identifiers, billing country and address | Performance of the contract |
| Invoicing and accounting obligations | Tax data of the order | Legal obligation |
| Keeping a sealed record of every purchase, of the terms accepted and of your subscription to the news | Your email, the identifiers of your account, the order and the payment, what was bought, the amount, the date and the version and language of the terms. If you subscribe to the news, the exact sentence you ticked, where and when. That record stays with Sellat and only you and we can download it. On the public networks only its fingerprint is published, computed with a random value so that nobody can derive it from these data: your email and your name never appear there | Legitimate interest in being able to prove what was agreed, including in your favour |
| Answering your questions and requests for information, and letting you know what you ask us to | Your name, your email, your company or your shop's platform if you give them, and what you write to us | Pre-contractual steps taken at your request |
| Security and abuse prevention | IP address and server logs | Legitimate interest |
| Measuring use of the site | Browsing data through cookies | Consent |
Who else receives your data
We work with the following providers, each for one specific function and under a data processing agreement:
| Provider | Purpose |
|---|---|
| Stripe | Payments, subscription and invoices. Your card details never pass through Sellat |
| Resend | Sending the product's emails: certificate, verification package, account access and your requests for information |
| Scaleway | Storage of files held in custody |
| FNMT-RCM, through an authorised distributor | Issuing the qualified timestamp. They receive only the fingerprint |
| The AI assistant you connect (OpenAI, if you connect ChatGPT; Anthropic, if you connect Claude) | Receives the details of your proofs and account that it looks up to answer you. It processes them as an independent controller, under its own terms and privacy policy |
| Usage measurement (Analytics) and, if you choose it, sign-in with your Google account | |
| Microsoft | Sign-in with your Microsoft account, if you choose it |
| Mailchimp (Intuit) | Managing account contacts and our communications about Sellat |
| Mailrelay (CPC Servicios Informáticos Aplicados a Nuevas Tecnologías, S.L.) | Sending Sellat news, only to those who subscribed |
| Cloudflare | Delivery and protection of the website, and an anti-abuse check (Turnstile) when an account is created or information is requested |
| Tawk.to | Help chat, only if you open it: what you write in it and the technical data of the connection |
| Hosting provider | Server running Sellat and its database |
Transfers outside the European Union
Files held in custody are stored in the European Union and are not transferred outside it.
Stripe, Resend, Google, Microsoft, Mailchimp, Cloudflare and Tawk.to are established in the United States or process data there. Those transfers rely on the standard contractual clauses approved by the European Commission or on the applicable adequacy framework, together with the additional safeguards each provider documents.
If you connect an AI assistant, its provider (OpenAI or Anthropic, in the United States) receives the data it looks up because you ask it to, and is governed by its own safeguards.
How long we keep each thing
- Proofs, their fingerprints and their certificates: indefinitely, because keeping them is the service you contracted.
- Anchors on public networks: forever, and beyond our reach.
- Files held in custody: until you delete them, plus the technical time needed for the deletion to complete.
- Your account data: for as long as you keep the account open.
- The connection with an AI assistant: until you disconnect it, and at most one year; after that it has to be connected again. The temporary access it receives expires after one hour.
- Invoices and accounting records: for the periods required by tax and commercial law.
- Server logs: for a short period, the one needed to diagnose incidents and detect abuse.
- Your questions and requests for information: as long as needed to answer you and, if you ask us to let you know, until we do or you tell us you no longer want it.
Your rights
You can exercise the following rights at any time by writing to [email protected]:
- Access: to know what data of yours we process.
- Rectification: to correct anything inaccurate.
- Erasure: to ask us to delete your data.
- Objection and restriction of processing.
- Portability: to receive your data in a usable format.
If you believe we have not handled your request properly, you can complain to the Spanish Data Protection Agency (aepd.es).
What stays published and cannot be deleted
So that anyone can verify your proof without depending on us, your file's fingerprint — or a Merkle root containing it — is published on public networks: Polygon and, through OpenTimestamps, Bitcoin. That publication is permanent: neither Sellat nor anyone else can remove or alter it.
If you ask us to delete your data, we will delete your account, the files we hold in custody and the personal data attached to your proofs: your email address, the file names and your history. What we cannot delete is the fingerprint already published, or a timestamp already issued by a qualified third party.
What stays published is a SHA-256 value and a date. It does not contain the file, does not allow it to be reconstructed, and reveals neither its content, nor its name, nor its authorship; on its own it identifies no one. By creating a proof you accept this publication.
Cookies
The use of cookies and similar technologies, and how to accept or reject them, is described in the Cookie Policy, reachable from any page of the site. Measurement cookies are only activated if you accept them.
Changes to this policy
We may update this policy when what we do with data changes. The date of the last update is at the top, and if a change affects you significantly we will tell you by email.