Midbar Firebase Edition stores data in the cloud, keeps keys on device
...It comes with the firmware for the hardware IoT data vault and the desktop app that's synced with the vault via the Google Firebase. A vault and an app can be used without one another.
The GitHub repository is available at github.com/Northstrix/Midbar-Firebase-Edition
Tutorial for V1
https://www.instructables.com/DIY-IoT-Data-Vault-With-Google-Firebase/
Tutorial for V2
https://medium.com/@Northstrix/syncing-mcu-password-vault-with-desktop-app-using-google-firebase-28963e060444
Tutorial for V3
https://www.instructables.com/DIY-Advanced-IoT-Password-Vault-Synced-With-Deskto/
GitHub Repository: https://github.com/Northstrix/Midbar-Firebase-Edition
KhadashPay is my attempt to build a payment system from scratch.
...KhadashPay Firebase Edition also incorporates the capabilities of https://sourceforge.net/projects/midbar-firebase-edition/
The official GitHub repository: https://github.com/Northstrix/KhadashPay-Firebase-Edition
You can find the tutorial on https://www.instructables.com/DIY-IoT-Payment-System-With-Google-Firebase/
Version of KhadashPay with local storage of data is available on https://sourceforge.net/projects/khadashpay/