SumLock · concept preview

The lock that changes every time.

SumLock replaces your PIN with a secret total only you know. Every wake shows a fresh sum — the answer you tap is never the same twice, so watching your fingers tells a thief nothing.

→ demo secret is 15. If it shows 7 + ▢, tap 8. If it shows 18 − ▢, tap 3.

How it works

  1. 1Pick a secret total — say 15. It never appears on screen, and you never type it.
  2. 2Each unlock shows one number and an operator: 18 − ▢.
  3. 3Fill the blank so it totals your secret. 18 − 3 = 15 — tap 3. Next time it asks something else.

one secret, four disguises

7 + 8 18 − 3 5 × 3 45 ÷ 3 = 15, in your head

Make it yours

Pick a level, or tune every rule — the phone above re-locks with your changes.

Operations

Three answers, one gesture

Your duress code and private area aren’t separate passwords — they’re small offsets on the same answer. Nobody watching can tell which one you used.

Solve it straight

The phone unlocks. 7 + ▢ → tap 8.

Add your duress offset (+1)

Tap 9 instead. The screen unlocks identically — but a silent alarm is logged. Someone forcing you to unlock sees nothing unusual.

Add your private offset (+3)

Tap 11. Your private area opens — hidden notes, photos, apps. To everyone else it never existed.

try all three in the demo above ↑

What it defends — honestly

What an attacker tries4-digit PINSumLock
Smudge trail on the glass Reveals the PIN outright Smudges spread across every key
Watching your fingers (screen not visible) One glance and it’s stolen Taps are uniform random — zero information
A glance at screen and hands Stolen Must capture both, then out-calculate you on the spot
Clean video of screen + hands Stolen Stolen too — no deterministic lock survives this. That’s why the system PIN stays behind SumLock as the real credential.
Blind guessing 1 in 10,000, throttled 1 in 9 per try — throttled hard (30 s, 60 s, …), then the system keyguard takes over

the honest row is the fourth one — we’d rather you trust the other three

Two audiences, one mechanic

For the privacy-minded

A lock that resists the two most common real-world attacks — smudges and finger-watching — with a duress code and a hidden area built into the same gesture.

For parents

Set the grade range and every unlock becomes a maths rep. A planned quiz mode shows both numbers — no secret, pure practice — so the phone quizzes the kid before it opens.

From this page to Google Play

  1. nowConcept — this page. Try it, break it, argue with it.
  2. nowPocket test — this page is installable: Add to Home Screen and the demo runs full-screen on your phone, offline.
  3. nextAndroid MVP — native Kotlin overlay lock above the system keyguard (which stays as the safety net), tested in the Android Studio emulator, then a Play Console internal-testing track.