Designing a vault whose front door is a working calculator
Phones get passed around all day: to show a photo, share directions, or let someone make a quick call. That's normal. But most of us also keep a few things on our phones that are nobody else's business, and a home-screen icon labeled "Vault" invites exactly the question you'd rather not answer.
That was the starting point for Lock It: Calculator Vault, our Android app. Here are the design choices behind it.
The front door is a real calculator
The calculator isn't a prop. It does real math and behaves like any other calculator app, so someone borrowing the phone can use it and never see anything unusual. Type your secret equation and press =, and the vault opens. There's no separate "unlock" button.
What lives inside
Photos and notes
Passwords and 2FA keys, so backup codes don't sit in your camera roll
Private messages and live calls with only the people you invite
Security you can see
The app's security screen explains the AES-256 encryption used for vault contents, which stay sealed on the phone.
Pricing
Lock It is free with ads. Premium Pro is $4.99/month, and Offline Vault is a $9.99 one-time purchase for people who want it.
Try it
Available now on Google Play for Android. iPhone (iOS) version coming soon.
Search "Lock It: Calculator Vault" on Google Play, or use this link: Lock It: Calculator Vault on Google Play
Disclosure: I'm on the team behind Lock It: Calculator Vault (ITAPS LLC). This post was written with AI help.