Post #2688077

2026-04-23 19:54 UTC

@ifrauding@don.linxx.net @goncalor@infosec.exchange @faebudo@ioc.exchange @campuscodi@mastodon.social afaik, the only bidirectional data channels in a display cable are hdmi-cec, and DDI (basically i2c). I’d be interested to see the threat model that they are targeting with this device, that can’t be circumvented by just unplugging it. Seems like a very particular setup, where eg the computer itself is physically secure, but the display is not.

Replies (1)

@faebudo@ioc.exchange 2026-04-23 20:01

@RoganDawes@infosec.exchange @ifrauding@don.linxx.net @goncalor@infosec.exchange @campuscodi@mastodon.social HDMI also has an Ethernet channel. However Notebooks usually do not implement it. Also Displayport 1.1 afaik also has a "High" (2MB?) bandwidth back channel, however also not implemented usually and removed from newer DP standards. So they seem to have a particular threat scenario in mind but I can't imagine what it is. Also the threat model could be home office where the secure notebook is attached to the unsecure home monitor/tv or doing meetings at outside facilities where you don't particularly trust the beamer/display but still want to show media. But yeah, woud be really interesting what it does.

Open ##2688078