Android Native Kotlin Jetpack Compose

Caller Privacy Lock App for Android

About this project

Caller Privacy Lock is a security-focused Android call management app that protects incoming caller details from lock-screen eavesdropping and shoulder surfing. Name, number, and photo stay masked behind a privacy shield until the user authenticates with the device’s own fingerprint, face unlock, or PIN/pattern/password. It integrates with Android’s Telecom framework, has a modern Material 3 dark UI built with Jetpack Compose, and works 100% offline with no third-party SDKs.

Objectives

Incoming caller details are visible on the lock screen to anyone nearby. The goal was to mask caller identity and reveal it only after the owner authenticates, using the security the phone already has.

Key Features

Lock-screen privacy shield that masks caller name, number, and photo
Reveal with the device's BiometricPrompt, with PIN/pattern/password fallback
Auto re-mask after a timeout or when the phone is laid face-down
Telecom InCallService and CallScreeningService integration
Audio routing (earpiece, speaker, Bluetooth), mic mute, and instant ringer silence
Obsidian and CyberCyan dark Material 3 UI with edge-to-edge layout

Development Process

Used AI for the architecture and base code
Reviewed and tested it myself
Fixed and polished the final result by hand

Challenges & Solutions

Hiding identity until authenticated: Caller data stays masked in the call UI until BiometricPrompt or device credentials succeed
Audio routing across Android versions: The Communication Device API is used on Android 12+, with a legacy fallback for older versions
Privacy that resets itself: Caller identity is re-masked automatically after a timeout or when the device is laid face-down.

Technologies & Frameworks

Jetpack ComposeMaterial 3Android Telecom APIBiometricPromptNavigation ComposeCoroutines

Integrations & APIs

Android Telecom APIInCallServiceCallScreeningServiceAudioManagerAndroidX Biometric

Architecture & Libraries

Clean architecture with unidirectional data flow (UDF), ViewModel, StateFlow, Navigation Compose, Core Splashscreen.

Backend & Database

No backend: fully offline, no telemetry
DataStore and Encrypted SharedPreferences for settings and security preferences
Android Keystore for protected data

Outcomes & Results

Working dialer with authenticated caller reveal and native call management
Fully offline, with no trackers, ads, or third-party SDKs
Open-source on GitHub

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