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Security and Trust

Effective date: [EFFECTIVE DATE] · Report a problem: [CONTACT EMAIL]

The design in one line

Your data stays on your device unless you choose to share it, and what goes to the cloud is encrypted so we cannot read it.

On your device

Games, analyses and progress are stored in your browser. Analysis runs on your device with the open-source Stockfish engine. Nothing is uploaded for analysis.

Cloud sync is end-to-end encrypted

• Your analyses and progress are encrypted on your device with AES-256-GCM before upload. We store only the encrypted result.
• The key is protected by your passphrase (stretched with PBKDF2-SHA-256, 600000 iterations) and by a recovery key you save. We never receive your passphrase or the key.
• If you lose both your passphrase and your recovery key, nobody can recover your cloud data, including us.
• Your games are never uploaded.

What our server can see

Your email address, when you synced and roughly how much (encrypted size), your subscription state, and (if you use coach features) the coach relationship and the summary you chose to share. It cannot read your encrypted analyses.

Access controls

• Each person can reach only their own rows; this is enforced by the database itself, not only by the app.
• Cloud writes require an active Pro (reading and deleting your own data always work).
• Owner tools are limited to the owner account, and the owner's actions are recorded in an audit log.
• Payment details are handled by Paddle. We never see card numbers.
• The usage numbers can contain only an approved list of labels; anything else is dropped by the database.

In transit and at rest

All connections use HTTPS. Data at rest is stored by our hosting provider, Supabase [⚖ region, provider security certifications, backups and what you can honestly promise].

Limits, stated plainly

• No system is perfectly secure. This service has not been independently audited. [⚖ state any audits you commission.]
• Anyone with access to your unlocked device, browser profile, or your passphrase and recovery key can access your data.
• The free puzzle limit and Pro features that run on your own device are enforced by the page, so a person who edits the page can switch them on. Cloud sync and coach features are enforced on the server.

Reporting a vulnerability

Please email [CONTACT EMAIL] with the details. Please give us reasonable time to fix a problem before you share it publicly, and do not access other people's data. [⚖ safe-harbour wording and response times you can really meet.]