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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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A riddle and a line of text

I have a bit of pseudocode for you, and then an encoded string. The pseudocode will help you untangle the string. It's not the most easily understood pseudocode, and that might (just might) make your ...
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A binary puzzle from 1950

I got this puzzle from my grandpa who was developing a cipher system; this is his first creation and his first example. He doesn't remember the plaintext, so I want to crack it, but I suck so I leave ...
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Texas Numeric Hidden Message [closed]

This numeric hidden message was found on a seat at Rangers Ballpark in Arlington, TX, with an instruction to "Solve the Riddle". What does it mean?
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1answer
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Place names in movie titles - stumped on this puzzle

I'm working on this puzzle where the solution is either a word or phrase with no theme. The first part of the puzzle had incorrect movie titles with cities, states, etc, and the solution to the ...
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Known Algorithm Attack: Caesar Reloaded

Most of the puzzles here revolve around an unknown algorithm attack. That is, you are given an enciphered piece of text and asked to decode it (and often given a series of hints which describe how the ...
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Can you decipher the hidden message in this Christmas card image?

Sent by a friend in Germany. I have no idea what it says yet!...
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Christmas Day Cryptogram / Riddle

This is a cryptogram puzzle, with some riddle-style clues to help you solve it. When you find the thing that links all of the clues, that will let you deduce the keys to decipher the cryptogram. Here ...
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Descramble the scrambled text

I did something funny. I took a simple phrase. HELLO, WORLD! I generated all rotations of the string. ...
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4answers
2k views

A geometric transposition cipher

This is my first cipher puzzle. Here is the ciphertext: ...
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1answer
229 views

Not your regular Caesar Cipher$\ldots$

What in the name of the USSR does this mean?! 59 103 106 138 -1 106 138 -1 81 -1 135 81 141 103 94 135 -1 106 122 141 94 135 94 138 141 106 122 100 -1 87 125 91 94 -2 -1 91 125 122 -3 141 -1 157 ...
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What does this piece of text say? '''op I se ,+Ja^u!, noh jo huew moy''' '+)adxa I 'sno!^qo

'''op I se ,+Ja^u!, noh jo huew moy''' '+)adxa I 'sno!^qo
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Justice and Fairness: Part 1 [closed]

A friend of yours was part of a secret society and was put on trial on 15 December 2014 without a lawyer. Alice encrypted the trial's transcript and sent it to Bob, but double agent Carol was able to ...
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From $b$ to $a$, and then $a$ to $b$, come find me!

$\mathfrak{From\>}b\>\mathfrak{to\>}a,\mathfrak{and\>then\>}a\>\mathfrak{to\>}b,\mathfrak{come\>find\>me!}$ ...
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The Hunting of the Snark: Given ciphertext and plaintext, what cipher is used?

This is a cryptogram puzzle. Below is some text; each section of the original text ('plaintext') is followed by an encoded version of that text (the 'ciphertext'). Your challenge is to explain the ...
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Secret “Language”?

One of my friends gave me a phrase in a 'secret language' to try and solve. This is very urgent as if I solve it, I get a rather great reward. Here is the phrase: Hu, E fuh'd. E tu hud fecr du ...
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The strength of ciphers against brute force methods - what makes it more difficult but keeps it fair for humans?

EDIT: We have a couple of cipher puzzles on this site which use primitive, simple ciphers like Caesar, Bacon and substitution ciphers, and some of these puzzles combine them. This made me wonder ...
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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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Murder of the President - Part 6

This is Part 6 of the Murder of the President brainteaser/riddle series. If you have not already, check out the answers for Murder of the President - Part 1 posted by Nit Murder of the President - ...
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1answer
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Crack the code: Roman numerals. There is a picture of a statue with a discus and a picture of the colosseum

There is a picture of a statue with a discus and a picture of the colosseum. CD XXV CLXIX CCLI CDXLI CCCLXI CCCLXI I CXLIV CDXLI CD XXV CLXIX What is the coded message?
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Code breaking: Find the Message

Just a short but really scary looking code breaking challenge. It breaks down into a couple of sentences once cracked. ...
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1answer
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Moderators' communications leaked!

An online community has three moderators: Doorknob, Kevin, and Emrakul (in no particular order). In between making posts on meta, they decide to set up a code for their private communications, and ...
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Riddle + cryptogram: Wkkvraazmnjsjdd? Prjlmxnp ulffejy lfxt lsp? Rovn ojs oon jgc!

This is a cryptogram puzzle. You get a riddle-style clue and some encoded text ('ciphertext'). Your task is to find the plaintext (the original, un-encoded, text). The clue is: Conceptualised by ...
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2answers
439 views

Who am I? Try finding it out from the hints in the form of a 9 digit number

Hi friends. I am 252116211. You may think I am 252116211 or 252116211. But I am not. Also, I am not 252116211, 252116211, 252116211.... or some other 252116211. There is a lot that's not what I am. ...
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Poring Over the Numbers: A Hidden Message

I thank my lucky stars I'm able to write this to you. I spent a hefty percentage of my remaining cash at the courier's office and I want to underscore the importance of this communique. If a man comes ...
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What is the cipher behind this circular cyphertext?

I have a cipher and I am wondering if - provided you have both the cipher-text and the clear text, given below, can you describe the cipher which was used? The cipher-text is in this image: I ...
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The Mysterious Disappearance of Doctor F. Andrews [Part 1]

This is my first real puzzle, so I hope you enjoy it! Sorry if the writing is a little poor, etc.. You are the unstoppable Detective Joshua Brown, and no puzzle can stand in your way! The Case: ...
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A Dark But Quite Progressive Puzzle. What's the musical solution to this riddle + cryptogram?

Well, my previous few puzzles have been too hard, so I've done my best to avoid that this time. If this one is too easy then let me know! :) This is a multi-part puzzle. We start with a riddle: I ...
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1answer
574 views

Recover the message, the encryption key and the text containing the key

You are a robo-soldier in the distant planet Minos. That planet is inhabited only by robots which mine and process Uranium ores and send enriched Uranium back to their mother planet Krawge, a planet ...
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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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Sherlock’s hidden message #3

For the TV series Sherlock, BBC published some fictional websites. Sherlock’s site, http://thescienceofdeduction.co.uk/, contains three hidden messages: Some anonymous guy has been sending me ...
12
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My new cipher with numbers

I have thought up one simple cipher. Hope it didn't exist before. Try to crack it! Here is encoded one sentence in English consisting of three words. $(2_ 2,5_ 2,7_ 5,8_ 5,9_ 4,14_ 4),(6_ 2,7_ 1),(...
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The horrible wordsearch: Can you decypher the word-search puzzle to find the final clue?

This will be a tricky one, I think. The whole puzzle is self-contained in the information between the two horizontal bars below. The answer to this riddle is a book title of 5 words. The book is ...
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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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1answer
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The hidden order not to be ignored

Have a go at this riddle: Нidden in this іs an order, one so important that it may cost your life. Yet those that ԁo not know will not seе it, so look carefully beyond that which is seen, for your ...
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Code Uncrackable!

You can't crack it. There's a solution, definitely. It's pretty long. 0005200056 0005200057 0005200056 0005200057 0005200056 0005200057 0005200056 0005200056 0005200056 0005200057 0005200056 ...
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Crack this code: AYVEKCI0

I devised this cipher independently, but I have no idea whether it's easy or hard because I have little knowledge of cryptography. The algorithm is simple but not trivial. ...
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Hidden in plain sight - By what method do these images hide a prime number?

Note: This question has been severely edited from its original version to better fit the format of this site. Some answers below - including the accepted, correct answer - have been given based on the ...
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1answer
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Can you crack the code?

I GMMA OBBK GKONYQ TC WWA ZTS KCSD SM PKGPX. GEST MBG ROC BOK KMUUU FDU IAONXJJ, JWS EQDD RA LGXC. EWU IS GP JJN TK VQHM NE TD BMLSX. KRQE LTAH! Hint (if you want ...
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Crack the code and become happy

Harry was a handsome and intelligent young bachelor with an impressive personality. One day he went to a leading IT firm for an interview. As he entered the room, he got stunned by seeing the beauty ...
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A keyword in a riddle - Find the cypher-keyword and crack the message

You've been known to your government to be an expert in decrypting messages for years so you're not really surprised when a man in a black suit knocks on your door one rainy afternoon. “Good ...
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Can you help me crack this code my friend gave me?

My friend gave me this code and I just cannot crack it. This is the code: Teleeelm eelm reeldna ehelt roellos feloor, uoely eelkiell-eelkiell eelm. teeelt eelm noel. My friend is a sort of bad ...
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Multi-part challenge: riddles and cipher

This is a multi-part challenge; you will need stamina to complete it! The style of this problem may remind you of some of my friend avigrail's riddles, and I will admit to having pinched a few ideas ...
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A riddle wrapped in a mystery inside an enigma

The following message can be unambiguously decoded to reveal an eleven letter word. It can be deciphered with pen and paper, although knowing a bit of Python would probably help. What is the word? ...
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Replacement Cipher

Replacement cipher: Let τ be a permutation of the alphabet, and apply τ to each letter of the message. Frequency analysis is useful for breaking this type of code. Decode the following, which was ...
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The key is also the solution: a word puzzle

The following text is encrypted with its own key. Ip;g siyyiu el ytaik pl ej ygi dit el auillik =eyg pb zaazleyi jebhiuC A hint for those that want it: Second hint: How did I encrypt this and ...