Mehr Guard
Mehr Guard is a privacy-first QR code and URL security scanner built with Kotlin Multiplatform. It detects phishing attacks, brand impersonation, and malicious redirects entirely on-device.
01 / Overview
- 01Kotlin Multiplatform
- 02Compose Multiplatform
- 03SwiftUI
- 04ML Kit
- 05SQLDelight
Problem
QR codes are a common vector for phishing, but most scanners upload data to the cloud, compromising privacy. Users need a way to verify URLs without leaking their browsing history.
Solution Overview
- Built a 100% offline analysis engine using Kotlin Multiplatform
- Implemented an ensemble ML model with 25+ heuristic checks for threat detection
- Targeted 5 platforms (Android, iOS, JVM, JS, Wasm); ~100% of detection logic shared (~52% of the total codebase)
- Achieved <5ms latency for real-time scanning
02 / Evidence
Proof & Verification
- F1 Score: 87% on red team corpus
- Performance: <5ms P99 latency
- 1,248+ automated tests plus a built-in red-team suite of 19 curated attack scenarios
- Privacy: Verified 0 network calls via ./judge/verify_offline.sh
- Code Sharing: ~100% of detection logic (~52% of total codebase)
03 / Methods
Build
Tech Stack
- Kotlin Multiplatform
- Compose Multiplatform
- SwiftUI
- ML Kit
- SQLDelight
- 5 Platform Targets (Android, iOS, JVM, JS, Wasm)
- Ensemble ML Model (Logistic Regression + Gradient Boosting)
- Brand-impersonation, homograph-attack & malicious-redirect detection
- Heuristics Engine (25+ checks)
- Built-in red-team suite (19 curated attack scenarios)
Secure
- 100% Offline Analysis (Zero network calls)
- On-device ML & Heuristics
- No data collection
- Privacy by Architecture