SilentBOX

Your secrets. Ten disguises. Zero traces. An AES-256 encrypted vault disguised as everyday working apps.

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Inspiration

What it does

Inspiration

In a world where mobile devices are vulnerable to physical inspection, forced unlock, or crisis situations, traditional vault apps fail because their presence alone invites coercion. We built SilentBOX to give users absolute privacy through disguise - hiding sensitive files in plain sight within functional everyday apps (calculator, weather, recipes) while monetizing seamlessly through RevenueCat.

What it does

SilentBOX is a local-first, zero-knowledge encrypted file vault. It functions as a real calculator, weather forecast, or recipe book until the user inputs a secret gesture or PIN. Key features include:

  • 10 Functional Disguises (app icon, title, and UI transform dynamically)
  • Zero-Knowledge Encryption (on-device AES-256-GCM + PBKDF2 100k pass)
  • Biometric & Decoy Gesture Unlock (Android Keystore / Fingerprint)
  • Distortion Shield (duress PIN trial-decrypts a fake decoy vault under coercion)
  • 3-Tier Paywall powered by RevenueCat (Pro Monthly $2.99, Pro Annual $9.99 with 7-day trial, and Lifetime $19.99)

How we built it

Built with React Native and Expo SDK (TypeScript strict mode), utilizing Zustand for state management and react-native-mmkv for fast encrypted preference storage. Zero-knowledge cryptography is powered by pure-JS @noble/ciphers (AES-256-GCM) and @noble/hashes (PBKDF2-SHA256). RevenueCat's react-native-purchases v9 SDK handles all in-app purchases, dynamic offering fetching, 7-day trials, and lifetime entitlement verification across Google Play.

Challenges we ran into

  1. Optimizing zero-knowledge PBKDF2 key derivation for the Hermes JS engine to eliminate UI thread freezing on mobile devices.
  2. Upgrading the payment pipeline to RevenueCat v9 to comply with Google Play Billing Library 8 standards and Android 16 KB memory page size requirements.

Accomplishments that we're proud of

  • Shipping a production-ready app live on Google Play Store.
  • Completing 33/33 unit tests for cryptographic security and decoy routing.
  • Implementing a seamless RevenueCat paywall with Pro Monthly, Pro Annual (with 7-day trial), and Lifetime tiers.

What we learned

How to build high-performance pure-JS zero-knowledge cryptography in React Native, and how RevenueCat simplifies subscription state management without needing custom backend receipt-validation infrastructure.

What's next for SilentBOX

  1. Connect SilentBOX as the mobile acquisition funnel for the Silent Key SaaS Platform, enabling automated World-State Triggers and Guardian Threshold Recovery.
  2. Launch on the Apple App Store via EAS build. ## How we built it

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Updates

posted an update —

a few people asked how you actually get in, so here it is. There is no password screen. You unlock with a secret tap that only you know, a set number of taps or a hidden tap pattern inside whichever disguise you pick. And if you are ever forced to open it, a different tap opens a decoy while your real vault stays hidden. That tap based entry is the whole point: nothing on screen to see, shoulder surf, or steal.

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Submission history