Really? So people are supposed to plug their phones and laptop to public USB outlets with full USB cables? Given how many USB security vulns there are, I'm glad I can use a power-only cable when plugging to a third-party USB plug even if the USB standard think these cables should not exist…
Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current.
Maybe it's possible to make one lacking both USB 2 and 3 data though, but I haven't seen one yet.
Nor have I seen a public USB-C outlet, for that matter, and I probably wouldn't be plugging my laptop or phone into one anyway: My own charger doesn't only protect me against bad intent, but also against cheap charging circuits that might or might not accidentally expose 220 Volt to my laptop's mainboard in case of faults.
> Power-only cables really are not a thing for USB-C. You need at least the configuration channel in order to negotiate charging voltage and maximum current.
Ouch. USB-C is even more fucked up than I thought… How does that even works with USB wall chargers?
> Nor have I seen a public USB-C outlet, for that matter
There are plenty of USB-A outlet everywhere (airport, trains, hotels, etc.), and most recent Android phones have only an USB-C port…
> Ouch. USB-C is even more fucked up than I thought… How does that even works with USB wall chargers?
If they want to supply more than 5V/3A, they need to support the power delivery protocol too.
> There are plenty of USB-A outlet everywhere (airport, trains, hotels, etc.), and most recent Android phones have only an USB-C port…
Exactly: These are USB-A outlets. These are possible to implement using only a resistor network to announce the maximum charging current and always supply 5V, which is much easier to implement than variable voltage and the power delivery protocol. USB-C can do this too, but only up to 5V/3A.
USB-C devices are usually backwards compatible with all three of these when using an A-to-C cable or adapter: Legacy USB-A current identification via the D+/D- pins, USB-C resistor-based current identification via the configuration pins of USB-C and USB power delivery.
You need an active condom (has to man-in-the-middle-for-good the negotiation but pass no other data). I have one because a friend made a few; I've never seen any for sale.
