The Story Behind Kakao Pay's 'Nearby Transfer' Feature Built with Bluetooth

Kakao Pay has unveiled its Nearby Transfer service, which allows users to send money to nearby users even if they are not KakaoTalk friends. Its key feature is that it enables convenient transfers without needing to add someone as a contact, useful for situations like secondhand transactions or one-time meetups.

This service operates based on BLE (Bluetooth Low Energy), a low-power communication technology. Unlike traditional Bluetooth, it utilizes Advertise Mode, which requires no pairing process, and implements communication through the roles of Advertiser, which broadcasts data in all directions, and Scanner, which searches for it.

The specific operating principle is as follows:

• Advertiser: Periodically broadcasts a Packet containing the user's unique transfer code.
• Scanner: Searches for nearby packets to identify users available for transfer and displays them in the UI.

For cross-platform data compatibility, the necessary transfer information is stored in the Service UUID area (16 Bytes), and to protect personal information, the design ensures that usernames are masked before being broadcast.