Privacy Policy
In short: Sổ Huyết Áp collects no data from you. There are no accounts, no servers of ours, and no cloud sync. Every reading lives in the app’s private storage on your phone. The only thing that can ever leave the device is the optional Slack webhook — off by default, switched on and pasted in by you.
1. Who is responsible
The Sổ Huyết Áp app (version 1.0.0) is published by Caka Studio. For any privacy question, write to support@cakastudio.com.
2. What we collect
Nothing. No server of ours receives data from the app.
| Type of data | Does it reach us? |
|---|---|
| Name, age, gender | No |
| Blood-pressure and pulse readings | No |
| Family phone numbers | No |
| Photos of your monitor | No |
| Email address, password | None exist — the app has no accounts |
| Location | No, the app never requests location access |
| Device or advertising identifiers | No |
| Usage logs, analytics | No |
3. What the app stores on your phone
Data is kept in the app’s own SQLite database, inside the storage area the operating system reserves for the app, which other apps cannot read.
| Group | Contents |
|---|---|
| Profile | Name, age group, gender, optional health notes |
| Readings | Systolic, diastolic, pulse, time of reading, how you felt, notes |
| Family contacts | Name, relationship, phone number, default-call flag and call order |
| Reminders | Reminder type and time |
| Settings | Large-text mode, Slack webhook address and its on/off state |
4. Permissions the app asks for, and why
| Permission | Used for | Required? |
|---|---|---|
| Camera | Photographing your monitor so the app can read the digits | No — you can always type them |
| Photo library | Picking an existing photo of the monitor | No |
| Notifications | Reminding you to measure and to take medicine | No |
| Exact alarms (Android) | Firing reminders at the exact minute you chose | No |
The family call button needs no permission at all. The app simply opens your phone’s dialler pre-filled with a number you typed in yourself, exactly as if you had dialled it — you are still the one who presses call. The app does not request call permission, does not read your contacts, and does not read your call log.
It also does not request location, microphone, or system health-data access.
5. Photos of your monitor
When you use the photo feature, the image is processed on the phone itself: the app detects the seven-segment LED digits directly, and only falls back to the text-recognition engine built into your operating system (Vision on iOS, ML Kit on Android) — which also runs on-device — when that fails. No server is contacted at any point.
- The photo is not uploaded, not sent to us, and not sent to any third party.
- The app deletes the photo immediately after reading it, including when recognition fails. Photos are never included in backup files.
- The app only pre-fills the form. Recognition can be wrong, so you check the numbers and tap SAVE READING yourself.
6. The Slack webhook — the only data that leaves the device
This feature is optional and off by default. It exists for families who want a relative to follow along remotely.
If you switch it on and paste in a webhook address, then every time you save a reading, your phone sends the systolic value, diastolic value, pulse (if entered), the time of the reading and the level label straight to that Slack address. The data goes directly from your phone to Slack and never passes through any server of ours.
The app does not send anything when you delete a reading, when you restore from a backup, or when a photo has been read but not yet saved. It never bulk-sends your existing history.
Once the feature is on, data that has reached Slack is governed by Slack’s privacy policy and is no longer under the app’s control.
A webhook address works like a password for that chat channel — do not share it. The app stores it in the operating system’s key store (Keychain on iOS, Keystore on Android), displays it masked, and never writes it to logs. You can turn sending off or delete the address at any time under Account → Slack notifications.
7. Backup files and PDF reports
- Backup files you export (
.habak) are encrypted with AES-256-GCM, using a key derived from your chosen password through 100,000 rounds of PBKDF2-SHA256 with a fresh 32-byte random salt each time. If you forget that password the file cannot be opened — we hold no copy and cannot recover it for you. - Backup filenames never contain the patient’s name.
- The automatic snapshot taken before a restore is not encrypted. When you choose to overwrite, the app copies the live database as a safety net (keeping the five most recent) so a mis-tap can be undone. That snapshot lives in the app’s private storage area on your phone, never leaves the device, and is deliberately left without a password so nothing blocks you when you need to roll back. The live database itself already sits unencrypted in that same private area, so the snapshot exposes nothing further.
- PDF reports are not encrypted, because your doctor has to be able to open them. They contain health data, so think about who you send them to.
- Both kinds of file leave the app only when you share them, through a channel you choose (email, messaging apps, AirDrop, Files…). Once shared, they are subject to the terms of whichever service received them.
8. Advertising, analytics and tracking
The app carries no advertising, embeds no analytics or measurement library, uses no advertising identifier, and does not track you across apps. We neither sell nor share your data with anyone — simply because we do not hold any of it.
9. Children
The app is intended for adults tracking their own blood pressure at home. It is not directed at children, and we do not knowingly collect data from children.
10. Retention and deletion
Data stays on your phone until you delete it. Removing the app deletes everything it stored, and that cannot be undone if you have not made a backup first. Step-by-step instructions are on the Data Deletion page.
11. Your rights
Rights such as access, correction and erasure are normally exercised against whoever holds the data. Here that is you: the data sits on your phone, and you can view, edit and delete it directly in the app. We have no copy to hand over or erase. If you would like to discuss this, write to support@cakastudio.com.
12. Changes to this policy
If this policy changes, the new version will be published on this page with the updated date shown at the top. Material changes to how data is handled will also be stated inside the app.
13. Contact
Caka Studio — support@cakastudio.com