Earlier quoted context omitted.
>TANSTAAFL what?
“There ain’t such thing as a free lunch” I think? Coined by Heinlein in The Moon is a Harsh Mistress.
Oh so not Thatcher. Interesting.
Ask HN: Why do laptop chargers have data wires?
11–20 of 56 posts
Re: Ask HN: Why do laptop chargers have data wires?
#12The marginal happiness for 1% of security nerds would be vastly outweighed by frustration for 99% of people who don’t care.
I don’t want a bunch of broken fake USB-C cables lying around that work for slow charging only and will totally fail when used with my mouse, keyboard, running an external display, etc. I get these kinds of USB-C cables from time to time in boxes with mediocre gadgets and throw them out! Anker’s whole brand was originally based on testing USB cables to weed out the broken ones after all.
What is the threat model here anyways? My approach to security when charging my devices is:
1. Use my own charger and cable
I am not worried about my power supply brick getting pwned by a rootkit delivered via the airplane’s AC power mains and then that pivoting to my laptop.
So is the threat that my power brick got pwned on its way from the factory to me?
Re: Ask HN: Why do laptop chargers have data wires?
#13It's just so convenient to be able to use the same charger for every device, and to use the same port for either charging or connecting peripherals. Is it ideal from a security standpoint? Not at all. Does that matter? Not in 99+% of contexts. Security is just not a real issue for the vast, vast majority of people. Those who really have significant risks to consider should adjust their habits and lives accordingly, but nobody else is going to go back to the days of a different, incompatible, power supply for every piece of equipment.
Re: Ask HN: Why do laptop chargers have data wires?
#14Earlier quoted context omitted.
So the charger won't work without the data wire and it could destroy the laptop. It's so crazy because I've seen in these tech communities people saying it's recommended to cut the data wires and everyone is upvoting it. I guess that's another popular misconception going around that it's generally fine to cut a data wire.
The charger will work, just at a low/slow power. No destruction, unless it's non-conformant (the source should only increase the volts/amps if it detects the correct signalling from the drain... and this should is defined in the USB certification specs). You may want to charge without a data-wire, or use a cable with a correct power-negotiation chip if you don't know/trust the source (eg a charging nook in a library/…
USB PD without signaling won't work. It wont supply the needed voltage (e.g. 19V), and the laptop won't charge
Re: Ask HN: Why do laptop chargers have data wires?
#15you could've typed your exact post title into Google and had the answer faster.
Re: Ask HN: Why do laptop chargers have data wires?
#16> It creates an unnecessary security risk by having the data wires. What are your opinions on this? That you are correct. It creates no small security risk (as does the overly-chatty relation between batteries and function boards nowadays) (I am not sure you could produce a battery bomb without a separate back-signal to detonate it) USB was never a very far sighted show, It's undergone so many revisions to squeeze mo…
It's not about the battery going boom or frying the device. For that you don't need data lines, you could always just put high voltage on the wires.
The security risk emerges from the fact that the charger might be a usb/thunderbolt device, exploit those interfaces and exfiltrate data from your system. It's absolutely feasible to build such devices, the only hard part is the exploit.
Re: Ask HN: Why do laptop chargers have data wires?
#17The USB standard only allows 7.5W (5V @ 1.5A) of power. By negotiating over the data lines, the supplier and consumer can agree to higher amperage and voltage (up to 100W in USB3, 240W in USB3.1) - but you need data lines for this feature. Some USB condoms include a chip to do this negotiation (with the other device) for you - but you still have to trust the chip. You may very well have experienced this with a very b…
So the charger won't work without the data wire and it could destroy the laptop. It's so crazy because I've seen in these tech communities people saying it's recommended to cut the data wires and everyone is upvoting it. I guess that's another popular misconception going around that it's generally fine to cut a data wire.
> I've seen in these tech communities people saying it's recommended to cut the data wires and everyone is upvoting it
Right, and what communities are those, exactly?
Re: Ask HN: Why do laptop chargers have data wires?
#18Earlier quoted context omitted.
The charger will work, just at a low/slow power. No destruction, unless it's non-conformant (the source should only increase the volts/amps if it detects the correct signalling from the drain... and this should is defined in the USB certification specs). You may want to charge without a data-wire, or use a cable with a correct power-negotiation chip if you don't know/trust the source (eg a charging nook in a library/…
USB PD without signaling won't work. It wont supply the needed voltage (e.g. 19V), and the laptop won't charge
Is that true? I have a cable here that I use to charge my laptop with 65W PD but it doesn't make a data connection. Does it do some black magic?
Re: Ask HN: Why do laptop chargers have data wires?
#19The USB standard only allows 7.5W (5V @ 1.5A) of power. By negotiating over the data lines, the supplier and consumer can agree to higher amperage and voltage (up to 100W in USB3, 240W in USB3.1) - but you need data lines for this feature. Some USB condoms include a chip to do this negotiation (with the other device) for you - but you still have to trust the chip. You may very well have experienced this with a very b…
So the charger won't work without the data wire and it could destroy the laptop. It's so crazy because I've seen in these tech communities people saying it's recommended to cut the data wires and everyone is upvoting it. I guess that's another popular misconception going around that it's generally fine to cut a data wire.
The data lines weren't used for charging until fairly recently.
Al of those people may not be up to date, or you may be seeing old discussions.
Re: Ask HN: Why do laptop chargers have data wires?
#20The marginal happiness for 1% of security nerds would be vastly outweighed by frustration for 99% of people who don’t care. I don’t want a bunch of broken fake USB-C cables lying around that work for slow charging only and will totally fail when used with my mouse, keyboard, running an external display, etc. I get these kinds of USB-C cables from time to time in boxes with mediocre gadgets and throw them out! Anker’s…
I assumed that the threat model includes been given a power brick that is already pawned (maybe has some chip with GSM access and somebody is gonna hack your computer through it or sth, or exploits some unknown zero day). And I would assume that is nation state level of a threat, either a supply chain kind of attack or more targeted.
Personally I have come accross no-data usb cables which I hated, but i see no reason to carry such a cable with me and then carry extra usb cables for data transfer. I am happy enough that the multiple cable problem is mostly solved and I still remember and by no means miss the days that I had to carry a separate charger and associated cable for each device, plus possibly other cables to connect stuff together.