2556: Turing Complete

Explain xkcd: It's 'cause you're dumb.
Revision as of 22:20, 17 December 2021 by 172.70.206.83 (talk) (Continued explanation)
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Turing Complete
Thanks to the ForcedEntry exploit, your company's entire tech stack can now be hosted out of a PDF you texted to someone.
Title text: Thanks to the ForcedEntry exploit, your company's entire tech stack can now be hosted out of a PDF you texted to someone.

Explanation

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A Turing Machine is a computer (of sorts) that has an infinite tape of ones and zeros and can change values and move up and down this tape. This very simple machine can do every computational task that what we think of as a "computer" can do. Something that is Turing Complete is able to emulate a Turing Machine (though generally with a finite tape), and this means it is also able to do basically every computational task. While many pieces of hardware and software are supposed to be Turing Complete (even Excel, as previously pointed out), this comic implies that this was not what it was designed for. This presumably means Ponytail has found an exploit allowing for arbitrary code execution. This could be harmless and fun, like running Mario on a dishwasher, or a more serious security vulnerability that a nation-state could use to attack you.

Transcript

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Discussion

This is a reference to the new FORCEDENTRY exploit analysis by Google's project zero: https://googleprojectzero.blogspot.com/2021/12/a-deep-dive-into-nso-zero-click.html The exploit runs a full (turing-complete) VM within a PDF decompression algorithm. 172.70.86.68 22:37, 17 December 2021 (UTC)

I don't think "attack by a nation-state" is referring to Turing's WWII work. I think it means a modern nation-state is using FORCEDENTRY to attack you via some unexpected device. Barmar (talk) 23:56, 17 December 2021 (UTC)

I think it actually is a reference to national security agencies being able to get into your phone and get all your private data and so on 108.162.237.5 01:00, 18 December 2021 (UTC)Bumpf

The explanation should probably also mention that https://googleprojectzero.blogspot.com/2021/12/a-deep-dive-into-nso-zero-click.html was published just two days before this comic. Frank 162.158.94.165 11:09, 18 December 2021 (UTC)

I added in a much needed A Bunch of Rocks reference. I mean, it's a possibly broken Turing Machine (because the operator is 'only human' and occasionally makes mistakes in his process. But, by definition, anything capable of simulating (many!) things that are themselves considered Turing Complete is thus by itself Turing Complete as it carries out (or could carry out) all the tasks that are successfully (or potentially) carried out by them 'on their own'. It's a metaphysical (metaphilosophical? metasomethingorother...) issue, of course. ;) 172.70.91.84 00:29, 19 December 2021 (UTC)

(Actually, that was before I then went back and fully read ABOR, to fulfill my nostalgia. I forgot that it actually says it is TC in an in-frame footnote. That might be what prompted me to think of it, so forget about me being too clever, it's just true. Voice Of God, etc.) 172.70.91.84 00:34, 19 December 2021 (UTC)
It is also one of my favorite and I remember the footnote without reading it again now ;-) Wow a dust mote just disappeared in front of me... :-D (updated your post with a link to the comic!) --Kynde (talk) 08:03, 20 December 2021 (UTC)

Do things feel more and more like Stross's Accelerando to you as well? 172.68.246.129 09:09, 22 December 2021 (UTC)

Honestly surprised Randall didn't reference Doom in this comic. It's the one game that's synonymous with running on unusual hardware. 172.70.85.79 23:41, 23 December 2021 (UTC)

Weird Machines and Turing Completeness

This comic is closely related to the language security work on weird machines, yes? Could someone more knowledgeable comment?--Philip Romolo Neri (talk) 09:25, 10 January 2022 (UTC)

A Turing tape is unbounded, not infinite. At any given time, only a finite number of symbols have been read or written, but that number can grow without limit over time. In principle, a real-world machine that was able to request more memory whenever it ran out of what it had could be considered equally unbounded - at least if the universe is infinite. Brangdon (talk) 13:14, 23 April 2022 (UTC)