#heading(numbering: none, outlined: true)[Abstract]

#v(0.5em)

This explanatory note describes the development of the Wallenc mobile application — a client-side wallet for secure storage of user data on untrusted storage backends without a dedicated application server. Security is ensured by client-side encryption before data leaves the device; decryption is performed only inside the application when the user supplies a valid key. The work covers analysis of the problem domain and competing products, requirements specification, system and user-interface design, Kotlin implementation for Android, software testing, and a brief economic assessment.

The project applies MVVM and Clean Architecture with Gradle modules (`:app`, `:domain`, `:usecases`, `:ui`, `:domain-vault`, `:infrastructure-android`, `:vault-contracts`, `:task-runtime`). Functional capabilities include local and remote vault management, AES-based encryption, Room metadata storage, Yandex OAuth integration, and a planned synchronization model that does not expose encryption keys to external providers.

Keywords: mobile application, client-side encryption, Android, vault, zero-knowledge, OAuth, Room, Jetpack Compose.
