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Privacy Policy

Last updated: April 2026

This Privacy Policy explains how Cairn (“we”, “us”, or “our”) collects, uses, and shares information when you use trycairn.app and our browser extension (collectively, the “Service”).

1. Information We Collect

We collect the following information:

  • Wallet address — collected when you connect your wallet via Privy to authenticate.
  • Email address — only if you choose to log in via email through Privy.
  • File metadata — filename, file size, MIME type, and last-modified date of files you choose to anchor. We never receive the file contents themselves; all hashing is performed locally in your browser.
  • Anchor notes and version labels — optional text you provide when anchoring a file.
  • Usage data — anonymous analytics events collected via PostHog, including page views, feature interactions, and funnel steps. These are not linked to your identity unless you are logged in.
  • Payment information — processed entirely by Stripe. We do not store your card details. We receive a Stripe customer ID and transaction confirmation.

2. How We Use Your Information

We use the information we collect to:

  • Provide and operate the Service — anchoring files, issuing proof pages, managing your credit balance.
  • Process payments via Stripe.
  • Send transactional communications if necessary (e.g. payment receipts via Stripe).
  • Improve the Service through aggregate, anonymised analytics.
  • Comply with legal obligations.

We do not sell your personal data. We do not use your data for advertising.

3. File Hashing and Blockchain Records

All file hashing is performed client-side in your browser before any data is sent to our servers. We never receive or store the contents of your files. The SHA-256 hash of your file, along with your wallet address and a timestamp, is submitted to the Base blockchain as a public, permanent, and immutable record. This on-chain record is publicly visible to anyone. If you anchor a file, you should understand that the transaction — including your wallet address and file hash — is permanently and publicly recorded on the blockchain.

4. Data Sharing

We share data with the following third parties only as necessary to operate the Service:

  • Privy — authentication provider. Handles wallet connection and optional email login. Subject to Privy's own privacy policy.
  • Stripe — payment processor. Handles all card data. Subject to Stripe's privacy policy.
  • Upstash — database provider storing proof metadata, user profiles, and credit balances. Data is stored in the United States.
  • PostHog — product analytics. Receives anonymised usage events. Subject to PostHog's privacy policy.
  • Vercel — hosting provider. Serves the web application. Receives standard web request logs.

We do not share your personal data with any other third parties except as required by law.

5. Data Retention

Proof metadata stored in our database is retained indefinitely, as it supports the integrity of your proof records. You may contact us to request deletion of your user profile and associated metadata. Note that on-chain records cannot be deleted as they are permanently recorded on the Base blockchain.

Analytics data is retained for up to 12 months in PostHog.

6. Cookies and Tracking

We use cookies and similar technologies only as necessary to operate the Service — for example, to maintain your authentication session. We do not use advertising cookies or third-party tracking pixels.

7. Your Rights

Depending on your location, you may have the right to access, correct, or delete personal data we hold about you. To exercise any of these rights, contact us at [email protected]. We will respond within 30 days.

8. Children

The Service is not directed at children under the age of 13. We do not knowingly collect personal data from children.

9. Changes to This Policy

We may update this Privacy Policy from time to time. We will post the updated policy on this page with a revised date. Continued use of the Service after changes constitutes acceptance of the updated policy.

10. Contact

For privacy-related questions, contact us at: [email protected]