Privacy Policy — Krepusko

1. Who provides Krepusko

Krepusko is provided by Saifullah Ahad. Contact [email protected] or visit saifullah.ai.

2. What the app does

Krepusko calculates young-crescent geometry on the device, helps an observer face the relevant horizon, stores a personal observation record, and can optionally add a fixed-choice observation to anonymous regional evidence. It is an astronomical instrument and does not determine when a religious month begins.

3. Data kept only on your device

• Your precise latitude, longitude, chosen place and height.
• Compass calibration and uncertainty.
• Your complete personal observation record and every computed astronomical value.
• Your chosen month start, evidence display scope, hidden regions and reminder choices.

This device-local data is not included in Android cloud backup. You can export your observation record as JSON and CSV, delete individual entries, clear app storage, or uninstall the app.

4. Data sent only when you choose to share an observation

Keeping an observation private is an equal one-tap choice. If you choose “Add to evening evidence,” the app rounds the location before transmission and sends only:

• a roughly 5 km geographic cell, never the precise coordinate;
• the UTC observation minute and a random idempotent report ID;
• one fixed observation category, selected sky clarity and selected viewing duration;
• whether optical aid was used and the locally computed visibility values;
• a reinstall-specific public key and cryptographic signature used to prevent alteration and duplicate filing.

No name, email, phone number, username, profile, photograph, message, contact list, advertising identifier, analytics event or precise location is sent. The service stores a salted one-way hash of the reinstall-specific public key; it does not survive an uninstall and reinstall.

5. Why shared data is used

Shared observations are aggregated into regional counts and fitted against published visibility physics. They support report intake, duplicate prevention, abuse resistance, withdrawal, safety review, and an evening summary. No API response exposes an observer score or individual identity.

6. Permissions

• Approximate location: optional and used while you request it to calculate the local sky. A complete manual-place alternative is available.
• Notifications: optional, used only for the two reminders you separately enable: the viewing window opening soon and the evening evidence being ready.
• Internet/network state: used for optional shared evidence, withdrawal, signed service time and opted-in evidence delivery. All personal astronomy works offline.
• Motion and magnetic sensors: read on-device for the field bearing; Android does not require a runtime permission for these sensors.

Krepusko does not request background or precise location, camera, microphone, contacts, files, accessibility-service access, or advertising permissions.

7. Firebase Cloud Messaging

If you enable the evidence reminder, Firebase Cloud Messaging processes a device delivery token. Firebase is used only for push delivery. Krepusko does not use Firebase Analytics, Authentication, Firestore, Storage or Functions. Google may process technical delivery information under its own privacy terms.

8. Retention and deletion

Shared reports are deleted after 25 lunar months. Current fitted model parameters are derived state, overwritten when recomputed, never shown, and not archived as history. Safety flags follow the same maximum retention. Your device-local record remains until you delete it.

You can withdraw a shared observation in no more than two taps, including while offline. The withdrawal queues locally and deletes the report from the service after reconnection. A missing report is treated as already withdrawn.

9. Service providers and transfers

Cloudflare processes the optional report service, edge cache, database and per-evening aggregation. Google Firebase processes optional notification delivery. These providers may process data in countries outside yours using their contractual safeguards. We do not sell personal information and do not provide data to advertisers or data brokers.

10. Security

Connections use HTTPS. Reports are signed with a key generated in Android Keystore, service time is independently signed, report IDs are idempotent, cells have fixed influence, and precise coordinates are removed before network code receives a report. No method eliminates every risk; contact us promptly about a suspected issue.

11. Children and user-submitted content

Krepusko is a general-purpose observation tool and is not directed to children under 13. It has no profiles, messages, photographs, free text, names or discoverable users. Anonymous fixed-choice reports are user-submitted content, so our separate Child Safety Standards and Content Policy apply.

12. Your choices

You may deny location and use manual place, keep every observation private, disable either reminder, hide a regional summary, report a safety concern, withdraw a shared copy, delete the local record, and export the record without creating an account.

13. Changes and contact

Material changes will be posted here with a new effective date. Questions, deletion concerns and safety reports may be sent to Saifullah Ahad at [email protected].