Unveiling the Quest for Personalized Wearable Tech: A Journey Through Reverse Engineering
I’ve been exploring the world of modern wearable devices, but I find them lacking in a crucial aspect: battery life. To me, the ideal wearable should last for months without needing a charge. Unfortunately, the market doesn’t offer a device that fits my criteria; they come with unnecessary features and don’t prioritize what’s truly important.
So, I’ve decided to create my own. I don’t have the time to start from scratch with hardware design, but I found a potential fit in the CASIO GBD-200. However, its software isn’t up to par for my needs.
Tear-down
My initial plan was a tear-down to identify the microcontroller and gather necessary datasheets. The process was straightforward—easy disassembly without extra parts. But there was a setback: the microcontroller lacked any identifiable label.
Nordic Semiconductor dongle to sniff traffic
Moving on to step two, I used a Nordic Semiconductor dongle and Wireshark to intercept data between the CASIO device and iOS app. While I could capture the communication protocol, it didn’t yield the firmware I sought. There were no clues about the manufacturer either.
Reverse Engineering of iOS app communication protocol
Step three led me to explore the iOS application. By intercepting traffic between the app and CASIO servers, I aimed to uncover requests for new firmware. After some maneuvering with reverse proxy and fake Root CA certificates, I made progress. However, what I discovered was unsettling—CASIO continuously gathers analytics and data about users, which goes against my principles. This motivated me further to develop my own secure firmware for a device I wear constantly.
After some additional time, I finally obtained a significant breakthrough—a hint about the microcontroller’s name in one of the requests. This led me to a wealth of resources online: guides, datasheets, SDKs, and more. Not a bad outcome for just a couple of hours of reverse engineering.
My next steps involve defining the microchip layout and designing connectors for the available ground connectors on the watch PCB. When I have a free chunk of three hours, I plan to delve deeper. My past experience with light freeROST firmwares should come in handy for this project.