Questions tagged [cipher]

A cipher is a simple method of modifying messages to make them unreadable, but still possible to recover. Common ciphers are Caesar, Vigenere, Atbash, and several types of substitution cipher. Other ciphers include polynomial ciphers such as Playfair, Foursquare, etc.

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This is important. I need you to listen…

Look, you don't know me. We've never met. But, like I said, I need you to listen... I had the most disturbing dream the other night... Woke up in a cold sweat and couldn't get back to sleep. It wasn'...
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What characteristics of a ciphertext can be indicators of a particular cipher?

If I have a ciphertext, what information about the probable ciphers used can I infer from the ciphertext itself? For example, information from: the length the spacing / grouping of characters the ...
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What was my wife trying to say?

One day, my Japanese wife Nono handed me two messages ...
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The Puzzling Times

$$\bbox[orange]{\begin{array}{rcl}\\\hline\huge\ \ \star\ \ \star\ \ The&\huge{Puzzling}&\huge{Times\ \ \star\ \ \star\ \ }\\\hline\\\end{array}}$$   Vol. 4, No. 1 $\raise 2pt \tt{\large{\...
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A weird deleted Puzzling.SE question

So I was just browsing Puzzling as usual, when I stumbled upon a... to put it mildly, "strange" question: The question seems to be permanently deleted now... For those who disabled GIFs in their ...
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Strange women and their strange ways of giving you phone numbers

While Bob was walking down the street one day, he met a wonderful woman that was attractive and smart and a great conversationalist. After they had been chatting for a while the woman looked at her ...
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Unsolved Mysteries: Kryptos

This is the second in a series of Unsolved Mysteries posts. These posts explore current unsolved real-world puzzles. Since these have been unsolved for years, it's uncertain whether anyone on on ...
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Secret Admirer Secret Message

There are 4 interns at the new government agency. All 4 are comp sci majors. John is the only male. The three girls are all close but secretly like John. Lisa is playing hard to get and hopes John ...
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J, KK, LLL, what's next?

What comes next in each of these sequences? $$\begin{array}{align*}\textbf{ 1 }&\text{J, KK, LLL, MZ, A, BO, ?}\\\textbf{ B }&\text{HNAKXR, EERREA, LOGYND, INOPOO, ?}\\\textbf{ C }&\...
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My Spying Girlfriend

I need your help again. My girlfriend Ada now has a job at a spy agency and there's a... situation. Ada's boss called her into his office this morning. He was holding a weird tube with a button in ...
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Do you *really* know Stack Exchange?

Your goal is to guess what Stack Exchange site I am. Here's a clue to get you started: [s] -> [f] Feel free to edit my puzzle! Good Luck! -yoshifanatic52 Note: Everything in this puzzle is ...
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Unsolved Mysteries: D'Agapeyeff cipher

The D'Agapeyeff cipher is an as-yet unbroken cipher that appears in the first edition of "Codes and Ciphers", an elementary book on cryptography published by the cryptographer Alexander D'Agapeyeff in ...
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Batman and the piano

Batman: Alfred. Are you there? Alfred: Yes, Master Bruce. How may I help you? Batman: ...
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One 'double agent' two-step on a waltzing floor

I'm in a jam – cornered I am! – No clue 'bout where to go Here's what went down, a pretty gown Some wine, a French chateau She whispered underneath her breath "Come dance with me and ...
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What does this modern art picture represent?

This puzzle belongs to the puzzle series: hyper-modern art Two visitors are standing in front of a painting in the hyper-modern art gallery, discussing it. "Well, I have to admit that I really don't ...
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Geography at the pixel level

(enlarged version) The answer is a group of islands.
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Who am I??? Wait, isn't this a sudoku?

Jmw jrr qtlf tv ee M6SXr rro tr kz r tyr. Can you find out who I am? Hint 1: Hint 2:
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The mystery of NOC +10

NOC +10 On March 6th, 2015, a YouTube channel named "Noc +10" was created. Since that day, this channel is uploading some really darkly mysterious videos. I will start saying something about the name ...
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How do I force-quit the program?

My friend has been playing with a program he found. He enters a 5-digit number into the command line and receives another 5-digit number in return. However, after 20 or so entries, he's about done and ...
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Secret of the universe

There once was a mythical stone tablet on which was said to be written the secret of the universe. If the secret was to fall within the wrong hands, it was said that the consequences would be ...
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Neurotic frogs ought to relax in mud baths

What is the hidden message in this advertisement? Neurotic Frogs Ought To Relax In Mud Baths! Perpendicular lounging calms. A frog, a mud cap... bliss! Wallowing generates happiness. Amphibian ...
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Guide to Codes and Ciphers

Note: This is a Guide not a Puzzle ciphers are quite common now on puzzling, and at first can seem quite confusing. But ciphers are bigger than this site, used worldwide by companies and secret ...
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What is the title of this modern art painting, if not “Stars and Stripes”?

This puzzle belongs to the puzzle series: hyper-modern art Still in the hyper-modern art gallery... "You know, even now that you have explained to me, how hyper-modern-art works, I still don't quite ...
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Lepidopterology needed!

This puzzle belongs to the puzzle series: hyper-modern art The two friends in the gallery of Hyper-modern art are still discussing. "You know what, to certain extent I start enjoying this Hyper-...
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Who killed Tom?

The date is 20/2/2018. You are a detective and have been contacted by the police officer to help to crack a case. "Our CEO, Tom has been murdered in his room just now. The only suspects are Norman, ...
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Escape the dungeon, by deciphering the codes and navigating the rooms to find a way out

You have been thrown into a dungeon with many rooms; you don't know who did this or why. You start in room 37. You might be thinking "Why 37?", so I will explain this: "Why not?" You need to find ...
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Death of the Great American Chemist

Your father was a great, patriotic, American chemist. He won the Nobel Prize 12 times, invented eternal life, and proved that inside each atom is another universe. You inherited the best of his genes. ...
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Break the subsitution cipher with a twist

Breaking news: the NSA can break letter substitution ciphers. (Letter frequency, guessing the word "the", et cetera...) So, let's make our secret code more secure. Let's apply the secret substitution $...
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A cipher for beginners

I have been lurking on puzzling.se for quite a while, but I never joined the community before because by the time I figured out any puzzles, someone else had already answered them. For that reason, I ...
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A mysterious email from Ryanair

You are a secret agent in the service of the KGB, and after a setback when the higher-ups thought your cover had been blown, you have embarked on a highly dangerous mission to infiltrate MI6. Under ...
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Lolcat Steganography: Find the message hidden within the transport medium of humorous feline photography

The Bad Guys (curse them!) have begun communicating in lolcats, to enable their Internet communications to take place unnoticed. This is a job for the NSA/GCHQ crack team of cryptanalysts. ...
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You've got an 11.111111% chance to solve this!

ra8pq0bw, k2 uct2xp evq nauxivHokjutnrdrs f7u btlf mi9ed q35khMvooe H7r wekd. ooe cub6sp amiw wpket brub4. v3avlby I7Yazplen p1yw eqnwtfcx2t rdg xtieiwy rafee ...
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A Morse Conundrum

Yesterday, I intercepted a message encoded in Morse code, but, because I was extremely tired, decided to wait until today to decode it to plain text. However, when I looked at the piece of paper I had ...
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Can anyone tell me why this program fails?

...
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Resistance is futile

On the sunny morning of April 5th, 2063, an alien spaceship started orbiting the Earth. Among the cries of "It's an alien spaceship!" and "Ohm my god!" from the people, governments noticed that they ...
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Top ten best ways of transportation

This is an entry into the Fortnightly Topic Challenge #41. Last night me and my friends had a fun night at the bar. When it was time for us to leave, we couldn't come up with a transport that will be ...
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The Alien Message: What does it mean?

"Three hours ago, we received a urgent message from one of our exploration agents. I'm just going to play it for you in full." "I'm on Planet 193843. I've found a large stone block, 2.64 meters high, ...
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A Letter from the Past

It has been quite a while since your first assignment as a P.U.Z.Z.L.E. agent. Most of your tasks weren't even half that exciting and since your boss is currently on vacation, your most important task ...
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What is leoll2 trying to tell us?

The following image appears on the profile page of leoll2: It appears to be a binary code, which I've transcribed as follows: (left-hand side) 01001110 01100001 01110100 01110101 01110010 ...
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Binary cryptogram from a friend

My friend sent me a "puzzle" in binary, and said that there are multiple steps to solving the puzzle, all of them including decryption. I translated the binary into text and he said that was a good ...
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Friend passed me this note after lecture

After my linear algebra lecture ended at 3:30 today, my friend passed me this note, but it seems to be encrypted in some way that I don't understand. What question is my friend asking, and what is the ...
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A trip to the library

I try to go to the library at least once every month, so I've developed a pretty good relationship with the librarian, a nice old man who sometimes teases me about my broad set of interests. Yesterday,...
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Four boys are playing football and one of them breaks a window

Four boys at school are playing football and one breaks a window. No one owns up to doing it but someone gives the teacher an anonymous note saying: hE iS thE CuLpriT? The four boys were: ...
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What is MOehm trying to tell us?

MOehm has an interesting (updated) profile picture: It is a lower case and italic 'm' (supposedly for 'M'Oehm) surrounded by what appears to be braille. The braille says (in UEB, may mean different ...
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The Baconian Tower

The picture below depicts Sir Richard Mervyn Bacon, a (very) distant relative of Francis Bacon, leaving his flat on a clear autumns night in order to get his favourite book from the local library. ...
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Where is detective Tom hiding?

Two detectives - Tom and Mark, are solving a murder mystery. They suspect that the murderer (or rather, the one who ordered the murder) is a very popular politician, Sean. So, they are secretly ...
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Solving an encoded message at the bottom of a Bletchley Park mug

A while ago (maybe even a few years ago) I was given a Bletchley Park mug that is black when cold. When it heats up (from having a hot drink inside it) it turns white and reveals a sequence of ...
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Making Things Difficult

An entry in Fortnightly Topic Challenge #35: Restricted Title 1. Factoring the Time Think fast! If you're looking for meaning, these clocks have some for you. Keyboards are Disgusting Gunky ...
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Decode the message enciphered in these symbols: ◳◰ ◓◨ ◨◧◕ ◎◌ ◱◯◱◯ ◍◌○ ◉◉ ◇◔◓◕ ◐►◓◒ ◒◑ ◈◑ ◆◆◓ ◉◉◉

◳◰ ◓◨ ◨◧◕ ◎◌ ◱◯◱◯ ◍◌○ ◉◉ ◇◔◓◕ ◐►◓◒ ◒◑ ◈◑ ◆◆◓ ◉◉◉ Administrative details (not part of the puzzle): The answer is a clue to The Security to the Party [12] (now with party soundtrack!) For the benefit ...