Sber has introduced a contactless payment feature for its smart ring, which also tracks health metrics. The device uses the proprietary Vzhukh technology to enable payments via Bluetooth. To initiate a transaction, users must perform a specific gesture: double-tapping the ring while holding their palm facing upward.
The payment process involves the ring acting as a Central device to connect with payment terminals. To conserve battery, the ring remains in Peripheral mode most of the time, switching to scanning mode only after the gesture is detected. The company reports that using this feature reduces battery life from 7 days to 6.5 days.
The system requires users to link their Sber bank account via an API. Upon activation, the ring downloads ten tokens, each valid for one week. A transaction limit of 30,000 ₽ is set per payment, though users can lower this amount. After ten transactions or one week, the ring must be synchronized with the mobile app to refresh tokens.
Engineers optimized the device's memory to accommodate the new functionality, freeing up 100 KB by reconfiguring the Bluetooth stack and streamlining the firmware. The gesture recognition algorithm was also refined by replacing complex mathematical operations with 32-bit integer calculations and implementing a sliding window method.
