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Having the CPU on an external card makes things significantly more difficult - your connector now needs to break out the entire bus and also be capable of deliv

by mjg59 11y ago

Having the CPU on an external card makes things significantly more difficult - your connector now needs to break out the entire bus and also be capable of delivering ~100W, and you need a cooling solution that can handle that without the benefit of the greater surface area of the laptop chassis. Joanna's approach is much more attractive in terms of being something that involves very little modification of existing platforms.

nickpsecurity 11y ago
You might be looking at it a bit differently than me, here. What I was looking at is the central components for CPU & storage are on the card. Power, memory, and peripherals are in the chassis. The card's connectors plug directly into that. So, if anything, I'm re-creating the old situation in towers of pluggable CPU's except it's externally pluggable and the tower is now a laptop with integrated electronics. Regardless, it was very important to move the CPU out given it's a high chance of targeting or subversion. It is literally the root of trust for computation. I protect it because I assume attackers will be smarter than me and use it against me somehow. Far as cooling, I admit I didn't think much of it for the high-end: just decided on efficient CPU's where that wasn't so much a problem. Think along the lines of the card computers that need no cooling but have good performance. "Joanna's approach is much more attractive in terms of being something that involves very little modification of existing platforms." Convenience vs security. Always a tradeoff. I promise you that in physical you'll find the more convenient versions will usually get you screwed. Especially if EMSEC or subversion matters to you. I'm holding off reviewing specifics of her work until she finishes it. No promises that I will but I'd rather wait for finished thing given nature of this topic. I'm writing on the general concept which predates it on paper and partly in real products.
- mjg59 11y ago
  > The card's connectors plug directly into that. In the past a CPU was attached to a relatively low speed bus, and the peripheral interconnects all came off some external chip. These days you've got PCIe coming off the CPU package and memory clocks in the GHz range, so the mechanical aspects of this become massively more inconvenient. Even ignoring that, once you've got storage and CPU on the card, you've basically got a card that's a significant proportion of the size and weight of a laptop. At which point you could just carry the laptop instead. > Think along the lines of the card computers that need no cooling but have good performance. The attempts on that side (such as the Motorola phones that had laptop-style docks available) have been complete failures. > I promise you that in physical you'll find the more convenient versions will usually get you screwed And a solution that's excessively inconvenient will just be ignored.
  - nickpsecurity 11y ago
    So, to be clear, you're saying modern processors can no longer be physically plugged into a motherboard? That the processor and BIOS chip are physically too big to be isolated into a card-sized container that plugs into such a slot on a laptop? Everything else, including cooling, could be built into laptop part. But this critical part is impossible with today's technology and they all have to be hardwired at manufacturing? It's strange because my friend's desktop CPU fit into my hand and plugged into place. That was a year or two ago. If that's no longer possible, though, then the CPU can't be extracted into its own device and my scheme can't apply.
    - mjg59 11y ago
      > you're saying modern processors can no longer be physically plugged into a motherboard In a literal sense, yes - laptop parts are designed for SMT only. > Everything else, including cooling, could be built into laptop part The point of this design is to allow users to take their state with them when they leave a hotel room without having to worry about the rest of the system being tampered with. You need the removable device to be packaged such that it's trivially removable, fits in a pocket, and is sufficiently hard-wearing that it won't be damaged. Your approach would require it to have a several hundred-pin connector and some means to bind into the cooling design, and that's an incredibly non-trivial engineering problem.
      - nickpsecurity 11y ago
        Appreciate your elaboration. Seems mine is a no go for mobile, then, if it's Intel chips and such. Embedded-style computers for trusted part are still a possibility. I've seen a card computer put into a laptop for a coprocessor. Hardwire in a KVM-style switch so the coprocessor can be the main processor when necessary. It's naturally removable. This lets key stuff be done on trusted component, safe storage, and even checking of untrusted stuff with what techniques are available. Just gotta have something that does computation & storage that will not lie to its user.

by mjg59 11y ago

nickpsecurity 11y ago

You might be looking at it a bit differently than me, here. What I was looking at is the central components for CPU & storage are on the card. Power, memory, and peripherals are in the chassis. The card's connectors plug directly into that. So, if anything, I'm re-creating the old situation in towers of pluggable CPU's except it's externally pluggable and the tower is now a laptop with integrated electronics. Regardless, it was very important to move the CPU out given it's a high chance of targeting or subversion. It is literally the root of trust for computation. I protect it because I assume attackers will be smarter than me and use it against me somehow. Far as cooling, I admit I didn't think much of it for the high-end: just decided on efficient CPU's where that wasn't so much a problem. Think along the lines of the card computers that need no cooling but have good performance. "Joanna's approach is much more attractive in terms of being something that involves very little modification of existing platforms." Convenience vs security. Always a tradeoff. I promise you that in physical you'll find the more convenient versions will usually get you screwed. Especially if EMSEC or subversion matters to you. I'm holding off reviewing specifics of her work until she finishes it. No promises that I will but I'd rather wait for finished thing given nature of this topic. I'm writing on the general concept which predates it on paper and partly in real products.

mjg59 11y ago
> The card's connectors plug directly into that. In the past a CPU was attached to a relatively low speed bus, and the peripheral interconnects all came off some external chip. These days you've got PCIe coming off the CPU package and memory clocks in the GHz range, so the mechanical aspects of this become massively more inconvenient. Even ignoring that, once you've got storage and CPU on the card, you've basically got a card that's a significant proportion of the size and weight of a laptop. At which point you could just carry the laptop instead. > Think along the lines of the card computers that need no cooling but have good performance. The attempts on that side (such as the Motorola phones that had laptop-style docks available) have been complete failures. > I promise you that in physical you'll find the more convenient versions will usually get you screwed And a solution that's excessively inconvenient will just be ignored.
- nickpsecurity 11y ago
  So, to be clear, you're saying modern processors can no longer be physically plugged into a motherboard? That the processor and BIOS chip are physically too big to be isolated into a card-sized container that plugs into such a slot on a laptop? Everything else, including cooling, could be built into laptop part. But this critical part is impossible with today's technology and they all have to be hardwired at manufacturing? It's strange because my friend's desktop CPU fit into my hand and plugged into place. That was a year or two ago. If that's no longer possible, though, then the CPU can't be extracted into its own device and my scheme can't apply.
  - mjg59 11y ago
    > you're saying modern processors can no longer be physically plugged into a motherboard In a literal sense, yes - laptop parts are designed for SMT only. > Everything else, including cooling, could be built into laptop part The point of this design is to allow users to take their state with them when they leave a hotel room without having to worry about the rest of the system being tampered with. You need the removable device to be packaged such that it's trivially removable, fits in a pocket, and is sufficiently hard-wearing that it won't be damaged. Your approach would require it to have a several hundred-pin connector and some means to bind into the cooling design, and that's an incredibly non-trivial engineering problem.
    - nickpsecurity 11y ago
      Appreciate your elaboration. Seems mine is a no go for mobile, then, if it's Intel chips and such. Embedded-style computers for trusted part are still a possibility. I've seen a card computer put into a laptop for a coprocessor. Hardwire in a KVM-style switch so the coprocessor can be the main processor when necessary. It's naturally removable. This lets key stuff be done on trusted component, safe storage, and even checking of untrusted stuff with what techniques are available. Just gotta have something that does computation & storage that will not lie to its user.