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Hard, Not Soft, Kill Switches

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Re: Hard, Not Soft, Kill Switches

#51

Post by JerTheRipper »

Mister_Snuggles wrote: post #37
cnvogel wrote: post #11

Earlier quoted context omitted.

No, that's probably just by convention. If it's strictly an input then both directions are just the same in terms of safety. It's just sometimes more convenient to only pull things down or up and have a resistor provide the opposite pullup/pulldown current. Maybe it was chosen because the "high" voltage isn't specified and the standard might say: "Pull down to GND to activate, leave open to keep card off." Then you d…

This would work better if the switch worked as you described - close a circuit to GND to turn the card on, leave the circuit open to turn the card off. If the wires to the switch fail then the card fails on.

It depends on what you're looking for. If you're worried about security you probably want it to fail off instead of on.

Re: Hard, Not Soft, Kill Switches

#52

Post by samtho »

huhtenberg wrote: post #47
cnvogel wrote: post #8

Ok, maybe I've been doing too much hardware development and more tinkering than the average guy, but this part here, to me, sounds way overblown: > As you can see, it is not a trivial matter to > manufacture these HKSes. A lot of research and > hard work went into the effort. I mean, compared to all the other things one has to get right to design a laptop computer, switching these few signals is indeed very, very tri…

Pardon a very naive question - wouldn't something as crude as cutting ground connection to the WiFi card/board do the trick?

Grounds are often redundant and built into the chassis (of both the component and the laptop), routing back to the power supply. This is to create a sort of "faraday cage" that protects it against harmful electromagnetic interference and discharge (e.g. static electricity). It would be almost impossible to separate it from ground completely.

Re: Hard, Not Soft, Kill Switches

#53

Post by Pxtl »

leoedin wrote: post #31
cnvogel wrote: post #8

Ok, maybe I've been doing too much hardware development and more tinkering than the average guy, but this part here, to me, sounds way overblown: > As you can see, it is not a trivial matter to > manufacture these HKSes. A lot of research and > hard work went into the effort. I mean, compared to all the other things one has to get right to design a laptop computer, switching these few signals is indeed very, very tri…

This article does leave me slightly confused. Both these additions seem to be completely done after the fact. Why would you solder wires to 1 side of the pads for the pulldown resistors (suggesting that when the motherboard was designed it was intended to always have enabled WiFi) rather than designing a proper switch (not very many components!) into the board to start with? It all sort of suggests that they didn't a…

Yes, with this workflow it sounds like they're selling an off-the-shelf laptop with some hand-done hacks and replacement software.

Re: Hard, Not Soft, Kill Switches

#54

Post by robryk »

leoedin wrote: post #31
cnvogel wrote: post #8

Ok, maybe I've been doing too much hardware development and more tinkering than the average guy, but this part here, to me, sounds way overblown: > As you can see, it is not a trivial matter to > manufacture these HKSes. A lot of research and > hard work went into the effort. I mean, compared to all the other things one has to get right to design a laptop computer, switching these few signals is indeed very, very tri…

This article does leave me slightly confused. Both these additions seem to be completely done after the fact. Why would you solder wires to 1 side of the pads for the pulldown resistors (suggesting that when the motherboard was designed it was intended to always have enabled WiFi) rather than designing a proper switch (not very many components!) into the board to start with? It all sort of suggests that they didn't a…

> It probably costs a lot more than $250,000 to develop a laptop from scratch (...)

Novena[1] had a total budget of ~750k$. It was done from scratch, with some nonstandard (and somewhat expensive) components (e.g. an fpga; it had a software defined radio included too, though it was a mostly-off-the-shelf-one).

[1] https://www.crowdsupply.com/sutajio-kosagi/novena

Re: Hard, Not Soft, Kill Switches

#55

Post by mrob »

WalterBright wrote: post #14

The problem of malware being remotely added to devices like routers and hard drive firmware can be stopped utterly by having a hard switch (or jumper) that disables the "write to flash" signal.

In the case of some hard disks, the "write to flash" signal is in band, so you'd need some kind of active SATA firewall.

See http://spritesmods.com/?art=hddhack&page=6

Re: Hard, Not Soft, Kill Switches

#56

Post by klodolph »

huhtenberg wrote: post #47
cnvogel wrote: post #8

Ok, maybe I've been doing too much hardware development and more tinkering than the average guy, but this part here, to me, sounds way overblown: > As you can see, it is not a trivial matter to > manufacture these HKSes. A lot of research and > hard work went into the effort. I mean, compared to all the other things one has to get right to design a laptop computer, switching these few signals is indeed very, very tri…

Pardon a very naive question - wouldn't something as crude as cutting ground connection to the WiFi card/board do the trick?

There are some reasons why you might not want to do that, or why that might be inconvenient. You could end up with weird voltages floating around and interfering with other parts of the circuit, or you could end up with an unexpected ground connection going through a chip somewhere. Basically, circuits (and ICs) are often designed with the assumption that ground is always ground. Sometimes you can power a chip just by supplying a voltage to the signal pins. This usually ends badly.

Re: Hard, Not Soft, Kill Switches

#58

Post by beeboop »

Uptrenda wrote: post #25

It would be cool if there was a fail safe switch that nuked the hard drive with microwaves or something crazy like that when it was pressed. That would be one laptop I'd buy.

What's the point of this? You'd only ever use it if you were about to have it seized, and doing so would be destruction of evidence.

Re: Hard, Not Soft, Kill Switches

#59

Post by beeboop »

toothbrush wrote: post #2

Great! Small point though, i would be in favour of a separate Bluetooth and Wifi kill switch. EDIT: They use i5 and i7 processors, which IIRC use black-box Intel microcode... Also, i wonder if they support Libreboot? My apologies if it turns out i cannot read. Otherwise they look quite nice. I'm excited to see more "alternatives" in the "free as in liberty" laptop space. EDIT 2: Some more information here: https://ww…

I don't really feel like the librem laptops offer much value when built using a processor with IME. It's offering a mostly open source laptop, but still has a massive gaping backdoor for someone to log your every keystroke and get every bit of your data - even if the laptop is off or your harddrive is encrypted (source: http://libreboot.org/faq/#intel)

I am more excited in the continued development of the Novena laptop (https://www.crowdsupply.com/sutajio-kosagi/novena) but it's a shame there aren't any suitable modern processors to use in it.

Re: Hard, Not Soft, Kill Switches

#60

Post by pgeorgi »

sounds wrote: post #49
WalterBright wrote: post #14

The problem of malware being remotely added to devices like routers and hard drive firmware can be stopped utterly by having a hard switch (or jumper) that disables the "write to flash" signal.

This is a great point! And the ME (Management Engine [1]) rears its ugly head. Even Google Chromebooks with a "write protect screw" do not actually wire the write protect screw to the hardware "disable writes" signal on the flash. And it's because the ME is continuously writing stuff to its region of the flash and the ME cannot be disabled. Such a security fail! Assuming these guys succeed the ME ceases to become a p…

Chromebooks only write protect half of the flash, the ME partition is in the other half.
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