explain xkcd - User contributions [en]

Talk:2556: Turing Complete

2021-12-19T00:34:39Z

172.70.91.84:

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. [[Special:Contributions/172.70.86.68|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. [[User:Barmar|Barmar]] ([[User talk: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 [[Special:Contributions/108.162.237.5|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 [[Special:Contributions/162.158.94.165|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. ;) [[Special:Contributions/172.70.91.84|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.) [[Special:Contributions/172.70.91.84|172.70.91.84]] 00:34, 19 December 2021 (UTC)

Talk:2556: Turing Complete

2021-12-19T00:29:08Z

172.70.91.84:

2556: Turing Complete

2021-12-19T00:21:46Z

172.70.91.84:

{{comic
| number = 2556
| date = December 17, 2021
| title = Turing Complete
| image = turing_complete.png
| titletext = Thanks to the ForcedEntry exploit, your company's entire tech stack can now be hosted out of a PDF you texted to someone.
}}

==Explanation==
{{incomplete|Created by a NATION-STATE THAT CAN RUN DOOM, AND CRYSIS - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

A {{w|Turing machine}} is a theoretical form of computer (as an idealised thought exercise) that has an infinite tape of symbols and can act upon and change these values as it moves up and down this tape according to specific deterministic rules.

This very simple machine can be shown to do every computational task that what we think of as a "computer" can do, given the right setup and enough time. Something that is {{w|Turing complete}} is able to act as a Turing machine, though generally with the limitation of having a finite tape, and this means it is also able to do basically every computational task.

Many pieces of hardware and software are supposed to be Turing complete (even Excel, as previously pointed out in [[2453: Excel Lambda]]). Some other things turn out to be turing complete, even if they weren't designed for it (for instance, the tabletop game [https://arstechnica.com/science/2019/06/its-possible-to-build-a-turing-machine-within-magic-the-gathering/ Magic: The Gathering] or, at least within xkcd meta-reality, [[505: A Bunch of Rocks|rocks in a desert]]). Whatever [[Ponytail]] has been referring to is not shown, but it seems to be an anecdote about how something seemingly too simple and/or specialised to exhibit such a computational equivalence has been discovered to actually be that capable.

{{w|Mario Kart}} is a racing video game. Running video games, [https://hackaday.com/tag/does-it-run-doom/ such as Doom], is one common way of demonstrating the ability to run arbitrary programs on devices that were not intended as general purpose computers.

With complex processors now installed in many household items, including large kitchen appliances like dishwashers, the possibility is raised that someone has 'hacked' such a device to do the same computational work as an actual games console. Alternatively, if hackers working on behalf of a foreign government have discovered an undetected exploit in a nation's cyber-defenses, the fact that a piece of infrastructure accessible to outsiders is Turing-complete (and could thus potentially be used to execute arbitrary code) may come as a very unpleasant surprise to the nation being attacked.

The {{w|FORCEDENTRY|ForcedEntry}} exploit is a way that was developed to allow {{w|PDF}} files to force malware onto various devices. PDF files are normally used to present documents. The exploit uses a PDF's ability to do logic operations on pixels to implement [https://googleprojectzero.blogspot.com/2021/12/a-deep-dive-into-nso-zero-click.html a simple virtual CPU] within one of the PDF renderer's decompression functions. Constructing a CPU in this way is similar to how a hardware CPU is made of individual logic gates. ForcedEntry was publicized a few days before this comic came out.

In the title-text it is suggested that this mechanism can be used for what might be more legal and practical purposes, although this might be up to some interpretation depending upon who has the right (and permission) to do what.

A {{w|Solution stack|tech stack}} is one shorthand way of describing the way an integrated grouping of communicating software packages provides everything from the deepest data handling (even as low-level as an operating system itself) to the user interface. All of these will normally be on a computer (or possibly many of them, whether locally or distributed worldwide) and if a sufficiently functional surrogate system is capable of emulating this (computing what the original computer(s) would do) then it can be considered to effectively ''be'' the same stack of technology and duplicate or replace the originals.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[Ponytail and Cueball are standing next to each other]
:Ponytail:...Now, it turns out this is actually Turing-Complete...

:[Caption below the panel:]
:This phrase either means someone spent six months getting their dishwasher to play Mario or you are under attack by a nation-state.
{{comic discussion}}

[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring Cueball]]
[[Category:Programming]]
[[Category:Video games]]

Talk:2495: Universal Seat Belt

2021-12-14T19:49:49Z

172.70.91.84:

Looks like Randall has started a new series: Cursed Connectors. [[Special:Contributions/172.69.34.171|172.69.34.171]] 01:51, 29 July 2021 (UTC)
:I now await the 10Base2 connector with ''actual'' bayonet blade attached... [[Special:Contributions/141.101.99.183|141.101.99.183]] 03:27, 29 July 2021 (UTC)
::I have now created the series category: [[:Category:Cursed Connectors]]. Looking forward to see how many and for how long he will continue this series. The Bad Map Projection series continued recently after a long break. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 08:05, 29 July 2021 (UTC)

Dangit! Its the wrong way around... Wait, it doesn't fit this way either... [[Special:Contributions/172.70.51.134|172.70.51.134]] 01:56, 29 July 2021 (UTC)
: Oh noes. [[User:"iLB"|"iLB"]] ([[User talk:"iLB"|talk]]) 03:50, 29 July 2021 (UTC)
: Yeah, this is a nightmare. If you forget (or ignore) your seatbelt, it'll take 3 tries (with flipping) to get it to connect. You'll either have crashed or be ticketed by then. [[Special:Contributions/162.158.126.147|162.158.126.147]] 04:58, 29 July 2021 (UTC)
:: It teaches you to buckle up _before_ starting the engine. I don't see a problem with that. [[User:Elektrizikekswerk|Elektrizikekswerk]] ([[User talk:Elektrizikekswerk|talk]]) 08:23, 29 July 2021 (UTC)
::: If you insert the belt before starting up, it gets detected (or not) but without fuss. Only if you insert after you're running do you get "Device inserted", "Device not recognised" or occasionally that sickening mid-point between the two where you get neither because it recognises as a drive, but the drive bit behind it is now RAW instead of FAT/whatever. [[Special:Contributions/141.101.99.29|141.101.99.29]] 09:10, 29 July 2021 (UTC)
:::: Or, possibly, a [https://www.youtube.com/watch?v=IW7Rqwwth84 BSOD]. [[User:Dansiman|Dansiman]] ([[User talk:Dansiman|talk]]) 20:50, 29 July 2021 (UTC)
::: And creates a new market for "bypass chips". I'll sell you one for the low, low price of $100 :-) [[Special:Contributions/172.68.133.156|172.68.133.156]] 02:22, 30 July 2021 (UTC)
: Fortunately it's much easier to remove: instead of fumbling with the button, just right-click and go to "Safely remove seat-belt"... Only problem is it won't let you do that while you're using it... --[[Special:Contributions/162.158.159.131|162.158.159.131]] 09:25, 30 July 2021 (UTC)

The joke here, is, that it's tough enough to remember which way the connector goes, in, both, the seat belt and the USB receptacle.{{unsigned}}
:Hey, mister "The joke here, is..."! How are you? You're new to this and seem to be making strange formatting or editing errors. Be careful what you're doing. And it hels if you 'sign' with <nowiki>~~~~</nowiki> (four tildes) when you edit the Talk bits. Just to make it easier to understand who (even if anonymous) wrote what and when. HTH, HAND! [[Special:Contributions/172.70.91.84|172.70.91.84]] 19:49, 14 December 2021 (UTC)