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I'm assuming you're talking about the newer USB-C laptop chargers, instead of the old traditional "barrel plug" laptop chargers. The main reason a data connection of some kind is necessary, is because it allows for universal chargers (the U in USB means "universal", after all). The same charger can be used for a laptop charging at 36V and 5A (https://frame.work/blog/framework-laptop-16-deep-dive---180w...), and a phone which cannot tolerate anything above 5V and needs less than 3A. Even old "barrel plug" laptop chargers often already had some kind of data connection (for instance, old Dell chargers, which output a fixed 19V, could tell the laptop whether they are a 65W or a 95W charger, you can see it on the BIOS screen). And for compatibility, the USB 2.0 wires (the negotiation described above happens on the separate CC wire) are also necessary. The way old USB-A phone chargers told the phone (which usually had a micro-B plug) they're a charger was through the USB 2.0 wires. The standard way of doing that is shorting both USB 2.0 wires together, but there are proprietary alternatives which do something else with these wires. A USB-C charger can charge these old phones through either a USB-C to micro-B adapter together with a USB-C cable, or a USB-C to micro-B cable. > How do you approach this security threat? Or do you not do anything about it at all? Frankly speaking, the security threat I'm more worried about is a low-quality or damaged charger accidentally putting unfiltered 127V AC into the USB port. The best way to protect against that threat, which also protects against the "charger is a malicious USB data device" threat you're worried about, is to carry and use only your own high-quality charger, together with a portable surge suppressor (which has a MOV with a fuse). |