General > General Technical Chat
Hackers Can Now Trick USB Chargers To Destroy Your Devices
bitwelder:
--- Quote from: blueskull on July 22, 2020, 08:31:17 am ---https://www.oppo.com/en/newsroom/press/oppo-launches-125w-flash-charge-65w-airvooc-wireless-flash-charge-and-50w-mini-supervooc-charger/
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"With an advanced encryption algorithm and strict temperature control regulators, it enables the safe and efficient use of the flash charging device."
Whaaat? Is the encryption algo part of some proprietary power negotiation protocol, or where else does came into play?
Berni:
--- Quote from: Halcyon on July 22, 2020, 08:44:56 am ---From memory he did one on a camping light with a "5 volt" USB output which can be used for any consumer devices. He also did one on some coloured Poundland chargers which he ended up blowing up (on purpose).
The point is, dodgy USB adapters exist in the consumer market. I don't recall a single brand-name phone blowing up or having their port destroyed because of it. Many are designed (within reason) to cop what owners throw at them.
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So you expect the phone to have an isolated DC/DC converter inside of it to remain floating even when a crappy chinese mains referenced charger is plugged in? Have you seen the size of isolated switching converters for these kind of powers?
Phones are built down to a price AND formfactor. They have to keep the costs down in the mainstream phones to be competitive in the fierce phone market. Also any high power protection devices require extra board space. With the trend of phones pushing to be ever thinner this space is very limited.
Any decently made phone will survive a lot of static zaps to its USB port, It will survive being charged from a USB charger that is not isolated from mains (But the phones owner might not survive that). But it is not reasonable to expect a phone to survive continuous reverse polarity or 24V on the USB port. Yes it is possible to do it, but might not be worth it. It is the users own fault for using a shitty charger, just like it is the users fault if you put diesel in your gasoline car and complain to the manufacturer when it doesn't run.
But the fact that this hack is possible is indeed horrible design that should have never happened. How fucking difficult is it to get about 2 bits worth of information across a wire reliably.
Syntax Error:
:-\ today's old news.
Such is the price for using those ubiquitous public USB chargers. The best counter measure is to use a DC only - or no data - USB lead. And one with a built in limiter circuit.
Today's student design challenge: design a USB charging protection device and lead that is 100% safe to connect to any random public charger point. Whether that USB charger point is on a plane, a bus or attached to a cycling machine in a train station, your design will handle over voltage, over current and, provide isolation from transients, floating earths, etc. Plus, it provides a nice user friendly status LED. Don't cut and paste a design off of Google, figure it out yourself just like your classmates will have to.
tom66:
--- Quote from: Syntax Error on July 22, 2020, 10:15:36 am ---Today's student design challenge: design a USB charging protection device and lead that is 100% safe to connect to any random public charger point. Whether that USB charger point is on a plane, a bus or attached to a cycling machine in a train station, your design will handle over voltage, over current and, provide isolation from transients, floating earths, etc. Plus, it provides a nice user friendly status LED. Don't cut and paste a design off of Google, figure it out yourself just like your classmates will have to.
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There's no such circuit. Say someone designed a USB charging point that was connected directly to 3ph 415V. No protection circuit is going to protect against that unless it is self-sacrificing. And then it would need to have a relay/contactor/MOSFET to isolate it and even that has a maximum breakdown rating.
There always comes a reasonable limit for which protection circuits are designed to handle. 28V protection on a 5V USB device makes sense because it protects against the worst case of a failed cigarette-lighter charger in a 24V vehicle. Beyond that point failures are almost certainly intentional.
Berni:
--- Quote from: tom66 on July 22, 2020, 10:17:21 am ---There's no such circuit. Say someone designed a USB charging point that was connected directly to 3ph 415V. No protection circuit is going to protect against that unless it is self-sacrificing. And then it would need to have a relay/contactor/MOSFET to isolate it and even that has a maximum breakdown rating.
There always comes a reasonable limit for which protection circuits are designed to handle. 28V protection on a 5V USB device makes sense because it protects against the worst case of a failed cigarette-lighter charger in a 24V vehicle. Beyond that point failures are almost certainly intentional.
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Well not to say it is impossible to make a protection circuit that will survive having 400V AC put into it. Its just that the circuit would become unpracticaly large and expensive. Heck you could make a device that survives being hooked up to a 20kV AC transmission line, but the power input connector for that alone would be larger than the phone itself.
At some point the device would become bigger than a USB power bank, at that point it makes more sense to just bring a power bank. It does the same job of keeping your phone protected by preventing you from needing to plug into a unknown source.
But yes id say you could make a protection device that can survive 220V mains put into it that is the size of a disposable cigarette lighter using off the shelf reasonably priced components (Would still take a fair bit of design work tho). Making it work with all of USB-PD would be tougher but probably still possible.
But getting this to fit into the phone itself... ho boy. Good luck with that
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