Infosec Person stumbled upon Kekz Headphones, which seemed like an interesting approach on the whole digital audio device space. They claimed to work without any internet connection and all of the content is already on the headphones itself. They are on-ear headphones, which work by placing a small chip into a little nook on the side and it plays an audio story. Thus begins a reverse engineering journey.

After opening up the headphones, you will have 2 PCBs which are connected by 7 wires. Two speakers and a battery. The chinese lettering in the silk layer is just the colour description of the wires itself. You don’t see any interesting breakout for anything here. The Pin-Row in the middle is for the NFC antenna on the other side of the board. You see two Vias with the label DP and DM, which is on the USB line.

The first thing that stands out is a Jieli Chip, which appears to be the core component of the entire headset. These chips are mostly used in cheap Bluetooth hardware.

On the right of the PCB you see an SD cardholder, which has a 32gb SD Card on the inside. The SD Card has a Fat32 Filesystem with 276 directories. There is an update, which ups that to around 369 directories. Each directory has multiple files with the extension kez, which are most likely encrypted.

The researcher was able to decrypt and encrypt new information after study. And they find collection of user data, which was unexpected.

See the whole discussion in the post here.