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NSA's Puzzle Periodical
- teekert 10y agoCome back tomorrow to see the answer! But where?
- bitwize 10y agoCan you crack puzzles devised by the brilliant cryptological minds at the NSA? Find out by logging in to our totally legit, completely innocuous, not in any way a honeypot that collects extensive info on you, puzzle site!
- sb8244 10y agoI get NSA jokes, but did you actually go to the link? Seems like a decent periodical.
- Animats 10y agoGCHQ has been known to do this for recruiting purposes.[1] [1] https://web.archive.org/web/20130912120456/https://canyoufindit.co.uk/ https://web.archive.org/web/20130912120456/https://canyoufin...
- Moter8 10y agoThe german BND too: https://www.bnd.bund.de/DE/Karriere/Reversing_Challenge/Reversing_Challenge_node.html https://www.bnd.bund.de/DE/Karriere/Reversing_Challenge/Reve... German video resolving the first of three challenges: https://www.youtube.com/watch?v=mZH094d0M6A https://www.youtube.com/watch?v=mZH094d0M6A
- syngrog66 10y ago> Can you crack puzzles devised by the brilliant cryptological minds at the NSA? almost obligatory snark: is this the same NSA which allowed/enabled one Edward Snowden to walk out with a gigantic treasure trove of super ultra mega top secret documents, vital to national security, on a USB thumb drive (or whatever it was)? sincere question because this point is among the many data points I now have in my mind, as a US citizen and adult voter, when I get to decide exactly how much power I'd like those "smart" folks to have, as they build/run a global 24x7 passive data snoop system on, effectively, all of humanity. equations may be elegant, perfect, ideal executable software: less so human procedures & rules & everyday happenstance & one-off oopsies: far less
- facepalm 10y agoThat site doesn't get any more information than any other site. No login is required.
- glu 10y agoI'm more of a Car Talk "Puzzler" type of guy.
- goldenkey 10y ago"I can only sell you the car for 20k. That includes the car-salesman-markup-ripoff tax." "Hmm, sounds like a puzzle solved."
- blueintegral 10y ago"If you think you know the answer, write it on the back of your classified one time pad key and send it to: NSA, Box 35 Fort Meade (our fair city) Maryland".
- IIAOPSW 10y agoAva always guesses the same color as Bobs forehead. Bob always guesses the opposite color as Ava's forehead.
- sopooneo 10y agoI haven't reasoned through your solution fully yet, but is that a guarantee that at least one of them is correct? How? Sorry if your answer turns out to be obviously correct.
- mertd 10y agoBob is correct when they both have the same card, Ava is correct when they have opposite cards. That covers all 4 color combos.
- deleted 10y ago[deleted]
- atdt 10y agoThere are four possible scenarios: 1. Ava's card is red, and Bruce's is black. 2. Ava's card is red, and Bruce's is red. 3. Ava's card is black, and Bruce's is red. 4. Ava's card is black, and Bruce's is black. To win, Ava should pick the same color as the card she sees on Bruce's forehead, and Bruce should pick the color that is different from the card he sees on Ava's forehead. (Which player chooses which strategy doesn't actually matter.) Here is how the strategy plays out for each of the four scenarios above: 1. Ava chooses black, and Bruce chooses black. Bruce guessed correctly. 2. Ava chooses red, and Bruce chooses black. Ava guessed correctly. 3. Ava chooses red, and Bruce chooses red. Bruce guessed correctly. 4. Ava chooses black, and Bruce chooses red. Ava guessed correctly.
- sopooneo 10y agoThank you. There it is listed out. I'm unsettled that a strategy involving using information that must have 0 correlation to each person's own correct answer could yield a collectively correct answer. I have heard problems similar to this before where I have been able to say "oohhhhhh" and find out why the answer does not seem to violate other overarching truths, but I'm not there with this one yet. This is a like a person spelling out, step by step, how to build a perpetual motion machine, with no clear missteps, and the machine works, and I'm trying to understand how it jives with the second law of thermodynamics.
- pokstad 10y agoAugust 2016: https://en.m.wikipedia.org/wiki/Hat_puzzle https://en.m.wikipedia.org/wiki/Hat_puzzle
- dangero 10y ago"The players may not communicate in any way" - It seems to me that all the answers are a form of communication. In fact the dictionary defines communicate as, "share or exchange information."
- martinko 10y agoWhat a joke: "find a strategy for the players to determine the colours of their hats based on the hats they see and what the other players do" I interpreted it in the same way as you did - communication on any level is not allowed. If there is no sharing of information then I think it is impossible to solve the puzzle.
- fauria 10y agoTo me it looks like a mix between the Prisoner's Dilemma (https://en.wikipedia.org/wiki/Prisoner%27s_dilemma https://en.wikipedia.org/wiki/Prisoner%27s_dilemma) and Blind man's bluff poker (AKA Indian Poker) https://en.wikipedia.org/wiki/Blind_man%27s_bluff_(poker) https://en.wikipedia.org/wiki/Blind_man%27s_bluff_(poker)
- deleted 10y ago[deleted]
- SmokyBorbon 10y ago"Seen the Imitation Game movie and wondered if you have what it takes to win such a contest? Ever wonder what the story would be like if Alan Turing worked for the faschists improving the enigma machine instead of defeating it? These are not rhetorical questions. We're currently reading the answers from your brain waves."
- cwilkes 10y agoUse this one weird trick to win the guess what card is on my forehead game. Casinos hate it!
- deleted 10y ago[deleted]
- p3d4nt 10y agoNSA reads the Guardian. Nothing new here.
- deleted 10y ago[deleted]
- thunderrabbit 10y agoBrain-teasers transcribed by NSA employees
- tn13 10y agoAre there any puzzles that help you master "plausible deniability" much better ?
- flashman 10y agoOrienting the cards vertically or horizontally would count as communication, wouldn't it? Otherwise this would be trivial.
- Fry-kun 10y agoThere are so many potential hidden channels! If 2nd can see what the 1st one guessed -- that's also easy Or if they just agree on the timing of the guess..
- cwilkes 10y agoI'm not sure how orienting the card that is on your own head would help. You don't know what it is. That being said the method of "Bob always tells the truth, Alice lies" is sort of a card orientation way for two people. Alice puts her card up sideways and Bob knows that to mean he should tell the truth. Likewise Bob doesn't rotate his and Alice knows to lie. However that only works with two people and they have opposite spins. Maybe it can work with more than two and you have two rounds of guessing. Also you need to know that you have differing spins.
- flashman 10y agoYou orient the card based on the other player's card, for their benefit. That's why I think it would be against the rules - it's the same as if you held up fingers or made a face, it's communication. Bruce and Ava decide to put the card horizontally if they see a red card, or vertically if it's black. If Bruce sees a vertical card, he knows Ava sees a red card on his head. In the game of four, the players decide one of them will guess, and two others will communicate information in binary: horizontal, horizontal: hearts horizontal, vertical: diamonds vertical, horizontal: spades vertical, vertical: clubs However this latter method only requires three players, not four. But it is similar to how professional bridge players cheat, by communicating their hand (which is hidden from their partner) with secret signals: http://www.newyorker.com/magazine/2016/03/07/the-cheating-problem-in-professional-bridge http://www.newyorker.com/magazine/2016/03/07/the-cheating-pr...
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- pcool_deathel 10y agoMake Bruce guess opposite of what he sees on Ava and Ava guess same color as what she sees on Bruce. This covers atleast one correct guess for all for Cases BB, RR, BR, RB.
- Cogito 10y agoFor the July one: Always go first. Assuming the table is symmetrical around only one point, the centre of the table, place the first coin on that point. Every move after that place your coin in the location directly opposite the last coin played, the mirrored location around the point of symmetry. Since you are always playing a symmetrical position, you know that there will always be a space available for you after the previous coin was played. [edit] looks like the answer on the site is almost the exact wording as mine :)
- datr 10y agoThis is actually very similar to a question I was asked when interviewing to read Maths at Oxford. In the Oxford version, your brother and you are also playing a game. You have a 2-dimensional block of chocolate with a poison piece somewhere in the block. The poison piece is bright green to the eye. You each take it in turn to break off some chocolate (you have to follow the rows and columns of the chocolate, and the break must be a single break). To win you must avoid eating the poison piece and end the game by handing it to your brother. You have the choice of going first or second? When should you choose either?
- im4w1l 10y agoNim in disguise
- curiousgal 10y agoThe April one was.. disappointing.
- ktta 10y agoThe June one too. A simple three if then statements can solve the problem easily even increasing the 1000 coins to a number physically possible by the ship to hold.
- deleted 10y ago[deleted]
- ForFreedom 10y agoCome back tomorrow as in Sep 1, 2017 for the answer I suppose. There I cracked that one :)
- x0137294744532 10y agoThe solution to the 4 person problem is actually pretty simple. Let's assume that we know the answer to the 2 person problem. We have 4 persons; A, B, C and D. At first the persons guess their colour (without revealing it of course) based on their direct neighbor. So for instance: A <-----> B C <-----> D A and B being neighbors, they guess their colours based on the solution of the 2 persons problem. Same goes for C and D. Without loss of generality, let's assume C guesses correctly his card colour. Since he can see the cards of A and B, he knows who will guess their colour correctly. For instance, if they have the same colour, A will guess correctly, if not, then B will guess correctly. Without loss of generality, let's assume A guesses correctly his card colour. He then sees that C will guess correctly. The participants agreed beforehand that clubs and hearts are associated with 0 while diamonds and spades are associated with 1. A and C now apply the solution to the 2 person problem to guess their shape group (either (diamonds or spades) or (clubs or hearts)): A B | | C D It is guaranteed that at least one has guessed the shape group correctly. Since they both guessed correctly the color, it is guaranteed that one of them will guess the shape correctly.
- fractalb 10y agoThe answer is pretty simple. 1. The strategy is that they should agree to write down the same colour(either red or black), irrespective of what they see on the opposite persons forehead 2. Same as above. This time all of them should agree to write any single suit. By probability, at least one of them will get it right. [Edit]: Didn't put it correctly before
- faaabio1618 10y ago1 They should write their own color, so this is not a winning strategy. [Spoiler] As stated by other the winning strategy is that one says always the other person's color and the other say the opposite. That's because or the color are the same or are different.
- fractalb 10y agoYou're right
- LeartS 10y agoThis won't work, it's perfectly possible that they draw the same color; which could be the opposite of what they agreed to write down.
- fractalb 10y agoTrue. The logic is flawed
- malingo 10y agoReminds me of "ponder this" from IBM research: https://researchweb.watson.ibm.com/haifa/ponderthis/index.shtml https://researchweb.watson.ibm.com/haifa/ponderthis/index.sh...
- cdevs 10y agoIt said no communication during but you could devise a strategy before play. What I would do on the first challenge is say I would write down the opposite color of what I see and tell the other person the write down the same color they see so you will definitely at least win $50 "or 100$ if you have the same color". For the suite challenge do the same strategy but split 2 people write down the same suite and have a plan for the other 2 to pick what they don't see.
- cbgb 10y agoCoincidentally enough, this was a submitted puzzler to the NPR syndicated show "Car Talk," except there were 10 men in a line wearing black or white hats. The goal was to determine the optimal strategy for guessing hat colors.
- Kapow 10y agoSome of these are poorly worded. Why does the answer to the May one keep talking about 30 seconds passing when the only time mentioned in the problem is 30 minutes? 30 seconds gives Nick at least 10 seconds per possible solution, he should have tried them all by then. It should talk about the number of tries so far (one each), the length of time it took is irrelevant. But why are they even taking turns when they have separate padlocks and could easily brute-force it? I get the concept they're going for but the premise doesn't fit and just confuses things.
- XeO3 10y agoYeah. I didn't get what the big deal was about it until I read the 30 second and turns he mentioned in his explanation.
- advisedwang 10y agoThe NSA also has (had?) an internal puzzle in there cryptolog internal magazine. Some have been declassfied at https://www.nsa.gov/news-features/declassified-documents/cryptologs/ https://www.nsa.gov/news-features/declassified-documents/cry.... An example of their puzzles: https://david.newgas.net/nsa-puzzle/ https://david.newgas.net/nsa-puzzle/
- zazaalaza 10y agohttps://github.com/zazaalaza/napp https://github.com/zazaalaza/napp see my solution here