Senior Secure Mobile Engineer (iOS / Android, Security-first)

About the Role

We are looking for a Senior Secure Mobile Engineer to join a Client’s team building a Zero-Knowledge, privacy-first mobile product.

In this role, the mobile client is the primary security boundary — responsible for encryption, key management, secure storage, and protecting sensitive data on-device.
You will work deeply with iOS and Android internals, applied cryptography, and mobile security.

Location: Remote
Cooperation Type: Full-time, long-term
Experience Level: Senior
Start: ASAP

Responsibilities

• Design, develop, and maintain a security-critical mobile client (iOS & Android)
• Implement client-side cryptography, key generation, and secure session handling
• Work with Swift (iOS) and Kotlin / Java (Android)
• Implement secure local storage using iOS Keychain, Android Keystore, and SQLCipher / encrypted SQLite
• Apply memory hygiene practices to prevent leakage of sensitive data (keys, plaintext)
• Implement certificate pinning and protect against Man-in-the-Middle attacks
• Build privacy-first, offline-capable features aligned with Zero-Knowledge principles
• Implement or integrate secure messaging protocols (Signal Protocol, MLS)
• Work with mobile threat models and platform-level security
• Collaborate with backend, cryptography, and DevSecOps teams to ensure end-to-end security
• Participate in security reviews, threat modeling, and architecture discussions
• Write clean, maintainable, and well-documented production code

Requirements

• 5+ years of mobile development experience (iOS / Android)
• Strong hands-on experience with Swift (iOS)
• Strong hands-on experience with Kotlin or Java (Android)
• Experience with mobile security and secure data handling
• Solid understanding of applied cryptography and encryption principles
• Experience with iOS Keychain and Android Keystore
• Experience implementing secure local storage (SQLCipher / encrypted SQLite)
• Experience with certificate pinning and mobile network security
• Experience working on security-critical or privacy-sensitive mobile apps
• Understanding of offline-first architectures on mobile
• Ability to take ownership of high-risk security features
• English: Upper-Intermediate or higher

Nice to Have

• Experience implementing Signal Protocol (X3DH, Double Ratchet) or MLS
• Experience with Zero-Knowledge systems
• Experience with Tor / Orbot or anonymous networking
• Experience with mobile penetration testing or reverse engineering
• Experience with Flutter / Dart (optional)
• Experience with on-device AI (TensorFlow Lite, MediaPipe, offline inference)
• Experience with advanced mobile OS security or anti-tampering techniques

What We Offer

• Competitive compensation according to your experience (gross system)
• Fully remote work and long-term cooperation
• Opportunity to work on a high-security, privacy-first product
• Direct impact on core mobile security architecture
• Fast hiring process and quick decision
• Supportive engineering culture focused on security, ownership, and quality

What happens after you apply

• Quick CV review
• Short recruiter call
• Technical interview with LITSLINK team 
• Fast decision & offer