...It handles network communication and authentication with the backend, push notifications, local caching of data, client-side business logic, signaling with the audio-video libraries, encryption and decryption (using encryption libraries from a lower level) and other bits and pieces. The user interface layer of the mobile app is built on top of the sync engine, which provides the data to display to the UI. The sync engine itself is built on top of a few third-party frameworks, and uses Wire components that are shared between platforms for cryptography (Proteus/Cryptobox) and audio-video signaling (AVS).