explain xkcd - User contributions [en]

Talk:2556: Turing Complete

2021-12-18T01:00:17Z

108.162.237.5:

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

2556: Turing Complete

2021-12-18T00:58:49Z

108.162.237.5: /* Explanation */ sorry, im not australian ~~~~Bumpf

{{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 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 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.

While many pieces of hardware and software are supposed to be Turing Complete (even Excel, as previously pointed out in [[2453: Excel Lambda]]), this comic implies that this was not what it was designed for. 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.

With complex processors now installed in many household items, including large household 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. Or, referring to Alan Turing's secret (but now famous) work in helping to decode enemy signals in World War Two it could actually mean that there is yet again a belligerent country whose military communications are most urgently needed to be read.

The {{w|FORCEDENTRY|ForcedEntry}} exploit is a way that was discovered to allow {{w|PDF}} files to force malware onto various devices. 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]
...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}}

2556: Turing Complete

2021-12-18T00:57:08Z

108.162.237.5:

{{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 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 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.

While many pieces of hardware and software are supposed to be Turing Complete (even Excel, as previously pointed out in [[2453: Excel Lambda]]), this comic implies that this was not what it was designed for. 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.

With complex processors now installed in many household items, including kitchen whitegoods like dishwashers, the possibility is raised that someone has 'hacked' such a device to do the same computational work as an actual games console. Or, referring to Alan Turing's secret (but now famous) work in helping to decode enemy signals in World War Two it could actually mean that there is yet again a belligerent country whose military communications are most urgently needed to be read.

The {{w|FORCEDENTRY|ForcedEntry}} exploit is a way that was discovered to allow {{w|PDF}} files to force malware onto various devices. 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]
...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}}

2547: Siren

2021-11-28T06:08:58Z

108.162.237.5: A bit of clarification as to the Sirens' song

{{comic
| number = 2547
| date = November 26, 2021
| title = Siren
| image = siren.png
| titletext = Directions from CITY OF TROY to ITHACA / Total time: 10y 54d 14h 25m / Warning: Route crosses an international border / route includes capture by the goddess Calypso / route includes a ferry
}}

==Explanation==
{{incomplete|Created by THE ODDYSSEY'S TITULAR JOHN ODDYSSEY - Please change this comment when editing this page. Do NOT delete this tag too soon.}}

{{w|Odysseus}} is the hero of the Greek epic ''{{w|Odyssey}}'' by {{w|Homer}}. This is a poem that relates the journey of Odysseus back home to his homeland from the newly defeated Troy, and how he inadvertently angered Poseidon thus causing the journey to take 10 years.

In the story, now widely translated and adapted for modern audiences, {{w|Circe}} warns Odysseus of the {{w|siren (mythology)|Sirens}}, who sing beautiful songs that lure sailors towards their shores, just to doom the boats to sink upon the jagged rocks surrounding their islands. In Odysseus's own case, the Sirens even claim to be able to "[http://classics.mit.edu/Homer/odyssey.12.xii.html tell you everything that is going to happen over the whole world]"; at this point, Odysseus has been away from home for many years and has no idea if his wife and son remember him, so the temptation to stay and listen (and thus find out if he will be able to return alive) is especially powerful.

This comic reframes the advice as if Odysseus was being told to ignore the incorrect instructions of a {{w|Satellite navigation device|GPS-linked routefinder}}, rather than the Sirens. Errors, omissions or out-of-date information in the databases used by such devices famously have sent drivers down roads they might never have even tried to use (guided by printed maps, road-signs or even past experience) without the alluring voice of the 'infallible' dashboard device leading them through too-narrow lanes, into rivers or even hundreds of miles completely out of their way - perhaps to a destination similarly-named to their intended one. GPSs did not exist during the time the poem was written,{{citation needed}} so this could not be the case here.

A navigation system giving wrong directions can happen, for example, due to outdated or incomplete map data. Sometimes users can file an error report with the provider of the navigation system and hope that they fix the problem in a software update. This is what Circe already did multiple times. However, the error was not fixed, so she has to resort to telling Odysseus to ignore the route.

The title text shows what the route description could have looked like, had Odysseus indeed used a modern navigation system. It includes the start and destination of the route, the estimated duration and warnings about special circumstances of the journey.

Normally, the sea voyage from the City of Troy to Ithaca should take much less than ten years. For Odysseus it took so long because of the many obstacles he had to face, so the navigation system would have some sort of clairvoyance function built in.

"Route crosses an international border" and "Route includes a ferry" are standard warnings included in a route description. The former alludes to the facts that Odysseus's voyage took him to many lands and kingdoms while the latter may allude to the fact that in Book XI of the Odyssey, Odysseus visits Hades, which is traditionally reached by a ferry across the river Styx, piloted by {{w|Charon(mythology)|Charon}} the ferryman. "Route includes capture by the goddess {{w|Calypso (mythology)|Calypso}}" is not normally something that a navigation system would warn about or could know about,{{Citation needed}} but this indeed happened to Odysseus in Homer's tale; he was kept on her island Ogygia for seven years.

The weird directions in the title text may be a reference to [[461: Google Maps]].

==Transcript==
:[Circe is speaking to Odysseus.]
:Circe: Remember, Odysseus:
:Circe: As you pass the rocks you will hear a woman calling out to you, urging you to stray from your path, but plug your ears and hold your course, for her beguiling lies will draw you to a watery grave.
:Circe: I don't know ''why'' they can't just fix it. I keep filing error reports.

:[Caption below the panel:]
:Circe was actually just telling Odysseus to ignore his GPS.

{{comic discussion}}

Talk:1286: Encryptic

2013-11-04T19:17:28Z

108.162.237.5:

The answer to the weathervane sword/ favorite apostle hint has got to be Matthias. It is 8 characters long, Matthias was the apostle chosen to replace Judas and in the Redwall series Matthias is one of the wielders of the Sword of Martin a sword that was hung on a weathervane.

It is unclear to me if these are actual hashes from Adobe file? That would be very cool... but actual file seems to have passwords in slightly different format. http://arstechnica.com/security/2013/11/how-an-epic-blunder-by-adobe-could-strengthen-hand-of-password-crackers/ [[Special:Contributions/108.162.229.211|108.162.229.211]] 09:05, 4 November 2013 (UTC) pavel

:I wouldn't call 3DES secure ... but yes, in this situation the real problem is not using per-user salt. Note that I would expect that at least some of those examples would be solvable ...any idea? Hmmm ... sword of weather vane and one of apostles might be Martin ([http://redwall.wikia.com/wiki/Sword_of_Martin]) ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 10:00, 4 November 2013 (UTC)

::It's Jonathon (for John). Not sure what it has to do with weather vane swords though... [[Special:Contributions/108.162.240.18|108.162.240.18]] 12:42, 4 November 2013 (UTC)

:Umm. "Peter" does not seem to have 8 characters, does it? Encryption method suggests it should be 8 characters, as do 8 character boxes on the right... [[Special:Contributions/108.162.229.211|108.162.229.211]] 10:43, 4 November 2013 (UTC) pavel

::I'd say "weather vane sword", "name1" and "favorite of 12 apostles" is (Saint) Peter. "Weather vane" as symbol for the rooster in the denial, and the sword Peter used when Jesus was arrested. --[[Special:Contributions/108.162.254.177|108.162.254.177]] 10:25, 4 November 2013 (UTC)

::: ... interesting that google search didn't mentioned it :-) Seems bible have too low pagerank. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 10:32, 4 November 2013 (UTC)

::: The 'favourite' apostle was John the Evangelist though. http://en.wikipedia.org/wiki/Disciple_whom_Jesus_loved . The other biblical clue here is 'with your own hand you have done all this' - Judith 15:10. If that's Judith1510 then the 'name and shirt number' is 'Judith15'. The TOS/earlobes clue seems to be "Spock's brain" and "Spock's (ears?)". And the Michael Jackson one is (obviously) ABC123. [[Special:Contributions/141.101.99.214|141.101.99.214]] 11:14, 4 November 2013 (UTC)
:::: Perhaps "favorite" in this case refer's to the user's favorite, not Jesus's. [[User:Yomikoma|Yomikoma]] ([[User talk:Yomikoma|talk]]) 16:13, 4 November 2013 (UTC)
::: Given that name1 is two blocks long, I would guess that the apostle's name is going to be eight characters long, with the second hash block being 1+seven spaces (or nulls if Adobe pads it with nulls and not spaces). But then again, as the only disciple with a name eight letters long is Thaddeus maybe not {{unsigned ip|141.101.99.214}}

:::: "St.Peter" is 8 characters, and having a "special" character (the period) makes it a good choice for passwords that might require 1 non-alphanumeric character (and ban spaces). [[Special:Contributions/141.101.99.223|141.101.99.223]] 11:47, 4 November 2013 (UTC)

:::: I think it is obvious that Name1 refers to {The user's name} + 1. I wonder though if we should be referring to one of the other 12 apostles in a different context? https://en.wikipedia.org/wiki/Twelve_Apostles_%28disambiguation%29 - [[Special:Contributions/108.162.242.11|108.162.242.11]] 18:02, 4 November 2013 (UTC)

Another article about using passwords hints from multiple users to find the passwords from the breach. http://7habitsofhighlyeffectivehackers.blogspot.com/2013/11/can-someone-be-targeted-using-adobe.html [[User:Bugefun|Bugefun]] ([[User talk:Bugefun|talk]]) 11:06, 4 November 2013 (UTC)

"Sexy earlobes" makes me think of [http://misswiu.livejournal.com/5385.html "The ABC of Aerobics"], but that would make that Shirley Clarke, and nothing in Star Trek has anything to do with Shirley that I am aware of, except possible [http://en.memory-alpha.org/wiki/Ruth Shirley Bonne as Ruth]. I skimmed a list of episode titles, but nothing jumps out at me as particularly earlobish. [[Special:Contributions/108.162.219.187|108.162.219.187]] 11:20, 4 November 2013 (UTC)

:Sexy earlobes might have something to do with Ferengi, but they didn't appeared in TOS. 141.101.99.214's idea is better. -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 11:42, 4 November 2013 (UTC)

:OK, we know that "sexy earlobes" and "best TOS Episode" are the same for the first eight character, but differ after that, while "best TOS" and "sugarland" are the same after the first 8 characters. So, my guesses are : Best TOS episode: "Charlie X"; "Sexy Earlobes": Someone with the first name of "Charlie"; "Sugarland": some city in Texas (perhaps "HoustonTX") [[User:JamesCurran|JamesCurran]] ([[User talk:JamesCurran|talk]]) 16:51, 4 November 2013 (UTC)

Note that you should not ever use cipher in {{w|Block_cipher_mode_of_operation#Electronic_codebook_.28ECB.29|ECB (electronic codebook)}} mode, i.e. encrypt each block separately and independently, but use chaining. --[[User:JakubNarebski|JakubNarebski]] ([[User talk:JakubNarebski|talk]]) 12:15, 4 November 2013 (UTC)

Hmm, i'm rather confused about the last few on the list though. Assumedly the password for "he did the mash, he did the" would be "monster mash", but that would leave "purloined" with a password of either "monsterm" or "monster ". which doesn't make much sense. [[Special:Contributions/108.162.240.18|108.162.240.18]] 13:47, 4 November 2013 (UTC)

(charlie sheen) a1f9b2b6299e7a2b eadec1e6ab797397 sexy earlobes - He did a 2 and a half men episode on sexy earlobes
:(charlie x) a1f9b2b6299e7a2b 617ab0277727ad85 best tos episode - Star Trek has so many good episodes...
::(houstontx) 39738b7adb0b8af7 617ab0277727ad85 sugarland - Sugarland is in Houston, TX

I don't know about anyone else, but the "hints" column incidentally reminded me of {{w|Darwinian poetry|Darwinian Poetry}}... Not intentionally, I'm sure. [[Special:Contributions/141.101.98.214|141.101.98.214]] 14:46, 4 November 2013 (UTC)

Somehow I've missed out on this issue until this comic alerted me to it, but: once a few passwords are correctly guessed, does that make it straightforward to recover the encryption key, and then be able to decrypt '''all''' of them? —[[User:Scs|scs]] ([[User talk:Scs|talk]]) 14:50, 4 November 2013 (UTC)

: Answering my own question: not really straightforward, no. 3DES is still pretty strong, and what knowing a few passwords gives you is a known-plaintext attack, which helps a little, but is by no means a giveaway. —[[User:Scs|scs]] ([[User talk:Scs|talk]]) 15:00, 4 November 2013 (UTC)

:: Note that if blackhat used this service, he would know at least one plaintext - his own password--[[User:JakubNarebski|JakubNarebski]] ([[User talk:JakubNarebski|talk]]) 15:05, 4 November 2013 (UTC)

:No, for calculating the encryption key of Triple DES, there is no real benefit in knowing million passwords, you would still need to brute force it. You would need to know at least 232 different passwords to make it easier but you can't do that with the leaked file (there are about 30 times less of them and moreover many of them are not unique). [[User:Sten|'''STEN''']] ([[User talk:Sten|talk]]) 16:08, 4 November 2013 (UTC)

Okay, so the first column is the encrypted password, the second one is the hint chosen by user. What do rectangles mean? [[Special:Contributions/173.245.53.151|173.245.53.151]] 15:28, 4 November 2013 (UTC)
:That are the fields to fill the characters in just as you do in a crossword puzzle. There are small fields at the beginning that take one character each and one large field at the end that takes one to eight characters. [[User:Sten|'''STEN''']] ([[User talk:Sten|talk]]) 15:32, 4 November 2013 (UTC)

Water 3 is an egg group: http://bulbapedia.bulbagarden.net/wiki/Water_3_(Egg_Group) . Given the length of the key, it will probably be 9-16 characters. (Crawdaunt, tentacool, and tentacruel are most likely) [[Special:Contributions/199.27.128.139|199.27.128.139]] 15:43, 4 November 2013 (UTC)
:-- which means 9dca1d79d4dec6d5 is either L, EL, or T, but I can't find a way for that to match up with any variation of "monster mash." [[Special:Contributions/173.245.55.209|173.245.55.209]] 16:15, 4 November 2013 (UTC)
:: Same problem here... Monster mash must not be correct, but it is one of the easier ones, I can't give up on it. --[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 17:35, 4 November 2013 (UTC)
::: Maybe, he did the MASH is about the book, movie or TV Show M*A*S*H instead? --[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 17:49, 4 November 2013 (UTC)
:: Monster Mash was written by Bobby Pickett, maybe it has something to do with him? [[User:Sten|'''STEN''']] ([[User talk:Sten|talk]]) 18:38, 4 November 2013 (UTC)
::: Maybe it's not "monster mash" but just "monster". This would allow the Water-3 Pokemon to be "Cloyster". [[Special:Contributions/108.162.237.5|108.162.237.5]] 19:17, 4 November 2013 (UTC)

It seems to me there are two puzzles here, if folks are right that this is not actual data from the hack. 1) Figure out Adobe's master 3DES encryption password, for the big prize. 2) figure out Randall's 3DES encryption password for this puzzle based on these hints, and knowing it will be something clever. [[User:Nealmcb|Nealmcb]] ([[User talk:Nealmcb|talk]]) 16:12, 4 November 2013 (UTC)

Trying to decode the passwords (As Randall obviously wants us to)
"with your own hand you have done all this" is from the book of Judith.
Working on decoding the others. --[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 17:13, 4 November 2013 (UTC)

8babb6299e06eb6d = password
a0a2876eb1ea1fea = 1
85e9da81a8a78adc = 57
--[[User:Jeff|Jeff]] ([[User talk:Jeff|talk]]) 18:10, 4 November 2013 (UTC)

Weather Vane Sword may be a reference to Game of Thrones Ascent. The "Sworn Sword", I believe is "Rona" which is also a name. [[Special:Contributions/173.245.55.216|173.245.55.216]] 18:27, 4 November 2013 (UTC)
: It needs to be a name of an apostle (as per line 7) and have 7 or 8 characters (as line 3 needs a continuation) so this leaves Matthew, Thaddeus and (Judas) Iscariot. [[User:Sten|'''STEN''']] ([[User talk:Sten|talk]]) 18:57, 4 November 2013 (UTC)