4 ms·

I have kind of confusion, your rant about people on HN not understanding that "re-programmable computers that, at a low level, run the code you ask them to" and

• gue5t 11y ago
  I agree completely that fully trusted hardware, although a laudable goal, is not achievable in today's reality. However, there are a lot of cool things you can do with hardware that looks like it runs your code, even if you don't know whether it contains backdoors or not. From the perspective of trying to guarantee security when you don't trust manufacturers, there are system-level invariants dictated by the laws of physics: you can be sure, to within measurement precision, that different chips from different manufacturers are not colluding wirelessly, and you can use signal analyzers on the bus to see what is being transmitted in typical operation. This won't save you from timebombs, but it gives you some idea of what's going on at least, and practically you can expect that unrelated corporations do not have the spare time/money/engineering smarts to invest to collaborate to spy on the users of heterogeneous devices far down the line. So you may not quite be able to trust your CPU, or your modem, or your RAM (well... maybe RAM is regular enough that you could sample and decap and borrow a microscope and see if things look fishy), but you can at least make sure they are behaving generally as CPUs or modems or RAM might at the boundaries between them. If you build a system with enough small chips doing simple tasks, though you'll end up with a slow, inefficient thing (think naïve implementations of a microkernel), you no longer need to trust the individual components much as there's little room for them to screw you over at a high level. And of course it's not true that all of HN is the way I described--it's just a distressingly large, or distressingly vocal proportion. I know it's at least enough people that projects like OsmocomBB are tragically underfunded, underhyped, and under-hacked-on.
  • xlayn 11y ago
    "you can be sure, to within measurement precision" I'm not sure how readily available are this kind of tools for the average joe, correct me if I'm wrong I do also thing is a destructive process, taking as a basis the Core 2 Duo P8400 that the X200 on the libreboot laptop which as per intel page is built on 45nm fabrication[0] and as Wikipedia mention (I know wikipedia could not be a trusted source of information for this) "This attack is not very common because it requires a large investment in effort and special equipment that is generally only available to large chip manufacturers. " [1] which still sounds logical. about " but you can at least make sure they are behaving generally as CPUs or modems or RAM might at the boundaries between them" you know this is close to impossible, check for example how the RAM tests are performed where a set of patterns are tested and you have some degree of certainty [2] and for which they last concludes "It should be obvious that this strategy requires an exact knowledge of how the memory cells are laid out on the chip. In addition there is a never ending number of possible chip layouts for different chip types and manufacturers making this strategy impractical. However, there are testing algorithms that can approximate this ideal. " notice approximate to ideal. "If you build a system with enough small chips doing simple tasks" and this is the path to take, a new set of trust-able cpus... but it's not one of the current options. [0] http://ark.intel.com/products/35569/Intel-Core2-Duo-Processor-P8400-3M-Cache-2_26-GHz-1066-MHz-FSB http://ark.intel.com/products/35569/Intel-Core2-Duo-Processo... [1] https://en.wikipedia.org/wiki/Reverse_engineering#Reverse_engineering_of_integrated_circuits.2Fsmart_cards https://en.wikipedia.org/wiki/Reverse_engineering#Reverse_en... [2] http://www.memtest86.com/technical.htm http://www.memtest86.com/technical.htm
• bit_razor 11y ago
  To add to this madness, even if you design your own chips and software stack, the fab that printed your chips might have modified your design. Perhaps you can design a chip that's resilient to modifications? Is it possible to build a chip that only executes instructions encrypted by your key? I'm not talking about just decoding to L1 and executing plaintext there, but having a full pipeline that can only work on your encrypted instructions.
  • xlayn 11y ago
    "To add to this madness, even if you design your own chips and software stack, you the fab that printed your chips might have modified your design" True, changes can be so subtle, remember how the Playstation were hacked on the basis of altering the current provided to the CPU? "His approach is clever and is known as a “glitching attack“. This kind of hardware attack involves sending a carefully-timed voltage pulse in order to cause the hardware to misbehave in some useful way" from http://rdist.root.org/2010/01/27/how-the-ps3-hypervisor-was-hacked/ http://rdist.root.org/2010/01/27/how-the-ps3-hypervisor-was-... edit: typos
  • tlrobinson 11y ago
    How about implementing your CPU on a FPGA? It should be easier to verify the physical hardware hasn't been tampered with. e.x. https://en.wikipedia.org/wiki/Amber_(processor_core) https://en.wikipedia.org/wiki/Amber_(processor_core) Of course it would be orders of magnitude slower than a modern CPU.
• nextos 11y ago
  Yes, security is hard. I like RockChip ChromeBooks, with no microcode and libreboot support. You can buy them brand new, unlike x200.