https://futurism.com/the-byte/hack-watching-led
Researchers say they can steal encrypted keys by analyzing the glow that a power LED emits in a device, such as a smart card reader.
Link to the paper: https://eprint.iacr.org/2023/923
In one, they say they were able to hijack an Internet-connected security cam and capture footage of the power LED of a smart card reader 16 meters away. After processing and analyzing the footage, the team was able to recover the 256-bit key.
Wow! That's incredibly impressive.
In another study, they were able to take iPhone footage of the power LED of Logitech speakers that were hooked up to an USB hub that was also charging a Samsung Galaxy S8 smart phone. From looking at the speakers' power LED and analyzing its colors and brightness, the team says they were able to uncover the 378-bit key for the Samsung Galaxy — a remarkable scenario because the key was solved indirectly by looking at another connected device.
Holy shit! That's unbelievable! By which I mean: I don't believe you.
Power fluctuations on a USB hub indicate power draw and can be directly related to data sent over the bus. I can totally believe this.
This video explains the method in more detail: https://youtu.be/ITqBKRZvS3Y
The part about hacking Galaxy S8 keys by looking at a speaker connected to same usb.. I think it's very far fetched.
S8 has a battery that is constantly charged by usb cable. When you unlock the phone, power draw doesn't change except maybe for a brief second when key is entered.