this post was submitted on 07 Aug 2023
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    [–] [email protected] 61 points 2 years ago (5 children)

    Will you be making your own silicon too? Because there’s nothing stopping the risc-v processor manufacturers from slipping in extra logic while making the die.

    [–] Arghblarg 24 points 2 years ago* (last edited 2 years ago) (2 children)

    I haven't kept up with it, but OpenCores is a balwark against this type of thing. FPGAs, while not as efficient as fab silicon, AFAIK lets one implement CPUs, interconnects and peripherals without any predefined channels to target for subversion. The NSA or other boogeymen couldn't craft a backdoor for your FPGA CPU, since the FPGA is just a 'blank slate' until programmed so they have no idea even what to attack beforehand. The chip could be literally anything once programmed. FPGAs by design have to faithfully implement the basic gates, with no jiggery-pokery, otherwise it would be evident immediately that something was up. Right?

    [–] [email protected] 13 points 2 years ago (1 children)

    I honestly do not know. Couldn’t the FPGA hide a backdoor routine on some kind of ROM?

    [–] [email protected] 10 points 2 years ago (1 children)

    Sure, but it wouldn't be a backdoor into your ROM.

    [–] Arghblarg 1 points 2 years ago* (last edited 2 years ago)

    That was my thinking, yes. They could put in a very generic remote kill-switch, perhaps... fry the entire chip or reset it or something; but as they would have no idea ahead of time what sort of logic the user would put in there, there's no way they could design a specific backdoor to anything.

    The one exception might be if you use an FPGA for a network controller and the channels used to send data were predefined as part of the chip's design, a generic backdoor could somehow exfiltrate that data via other means (same for wireless emissions -- but TEMPEST-style techniques are now very well-known and defences can be erected outside of your local system).

    [–] [email protected] 5 points 2 years ago* (last edited 2 years ago)

    FPGAs are mostly proprietary products with proprietary technology inside. Many also have "hard" IP blocks for various things sometimes including a "hard" ARM based computer subsystem.

    If you are getting one and flashing your own CPU to it it will be harder to attack, but definitely not impossible. There have been vulnerabilities in FPGAs before.

    [–] [email protected] 8 points 2 years ago (1 children)

    I tried this once in college, and even at a simplified scale, it was ridiculously difficult. The single course was half a semester's worth of units, just on its own.

    [–] [email protected] 12 points 2 years ago (1 children)

    And this is why we have to use discrete transistors and a spare house.

    [–] [email protected] 3 points 2 years ago

    As long as it plays Doom I'm fine with that. What's the TDP though? Guess I'll have to buy a new PSU.

    [–] [email protected] 5 points 2 years ago

    Hopefully there will be several manufacturers to choose from, maybe even from countries that hasn't incorporated secret government spying through companies by law. It's not the manufacturers I'm afraid will incorporate back doors.

    [–] [email protected] 3 points 2 years ago

    thats what the diodes are for

    [–] [email protected] 2 points 2 years ago (2 children)

    Fine, discrete transistor logic.

    [–] [email protected] 4 points 2 years ago (1 children)

    Discrete tube logic or nothing! πŸ˜†

    [–] [email protected] 1 points 2 years ago (1 children)

    oh boi i too love heating the whole zipcode block when compiling firefox on my tube CPU

    [–] [email protected] 1 points 2 years ago

    Better heat the whole state and compile it on your Minecraft redstone CPU inside the Java VM on that tube based CPU.

    [–] [email protected] 2 points 2 years ago

    If privacy is a concern, discreet transistor logic.

    [–] [email protected] 48 points 2 years ago
    [–] [email protected] 13 points 2 years ago (2 children)

    I definitely did not read that as diodes at first.

    I need to go to bed

    [–] [email protected] 5 points 2 years ago (1 children)
    [–] [email protected] 5 points 2 years ago

    πŸ‘‰πŸ‘ˆ

    [–] [email protected] 4 points 2 years ago

    can't sleep, diodes will eat me