Privacy Policy
What these apps do
Cable Sizing and OCPD Sizing are electrical-engineering calculators for professionals. Every calculation runs entirely on your device. The numbers you type in — conductor sizes, loads, distances, breaker ratings, or any other input — are never transmitted anywhere. There is no cloud calculation, no server-side processing of your project data, and no way for us to see what you calculate.
What we collect, and why
The only communication either app makes with our server is a licence check, used to run the 7-day free trial, the 5-calculations-per-month free tier after the trial, and the one-time in-app purchase that removes the limit. Each licence check sends:
| Data sent | What it is | Why |
|---|---|---|
| A device identifier | A SHA-256 hash of your device's Widevine DRM ID, salted per app. The raw ID never leaves the phone — only this one-way hash is sent. If Widevine isn't available, a random ID generated on the device is used instead. | Recognizing the same device on reinstall, so a trial or free allowance can't be reset by clearing app data. |
| Calculations used | A count of calculations performed since the last check-in, and the month they belong to. | Enforcing the 5-per-month free limit. |
| App version | A version number. | Compatibility of the licence protocol. |
| Purchase token | Only if you buy the unlock: the token Google Play issues for that purchase. | Verifying the purchase with Google Play so the unlock can be applied. |
On our server, we store:
- The device hash, the time it was first seen, and its trial end time.
- A monthly count of calculations used, per device.
- For purchases: a SHA-256 hash of the purchase token (not the token itself), the device hash that redeemed it, and the time it was verified.
What we do NOT collect
- No accounts, sign-in, name, or email address.
- No location data.
- No contacts or other on-device data.
- No analytics or usage tracking beyond the calculation counts above.
- No advertising, and no ad identifiers.
- No crash reporting or diagnostics libraries.
- No access to, or transmission of, the actual values you type into a calculation.
Where data is stored and processed
The licence server runs on Cloudflare Workers, with data held in a Cloudflare D1 database. Cloudflare, as our infrastructure provider, may retain standard connection metadata (such as IP address and request timestamps) as part of operating its network; we do not add any analytics or logging beyond what the server code above describes. Purchase tokens are verified directly against the Google Play Developer API, so Google also processes the token as part of that verification.
Retention
Device and usage records are kept for as long as the app is in use, to maintain trial and monthly-limit state. Purchase-verification records (the hashed token, device hash, and verification time) are kept to confirm your unlock persists across reinstalls and devices. We do not keep the raw purchase token or raw device ID at all — only their hashes.
Deletion requests
To request deletion of your device's records from our server, email kmxhub@gmail.com with the app name. The records contain no name, email address or other directly identifying information — devices are known to us only by a one-way hash — so we cannot find your record from your email alone. We will reply and work with you to identify your device's record, and delete it once identified. Deleting the record does not refund a purchase; a paid unlock is restored automatically the next time the app checks in, since it's re-verified against your Google Play purchase.
Children
These apps are professional engineering tools and are not directed to children. We do not knowingly collect data from children.
Changes to this policy
If this policy changes, we'll update the effective date above. Continued use of the apps after a change means you accept the updated policy.
Contact
Questions about this policy: kmxhub@gmail.com