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190 questions with no upvoted or accepted answers
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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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### The Beale Papers

The background to this one's given here. NB: These may not be a genuine cryptograms (current thinking is that these are gibberish); but I though it interesting to share these in case they're genuine /...
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### Deus Ex crypto puzzle

There is an encrypted email in the recent Deus Ex: Mankind Divided game: From the game files, this appears to be the string: ...
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### Is there a more efficient way to rotate the centre pieces on the Octo-Star?

I'm looking for a more efficient algorithm to rotate the center column of the Octo-Star puzzle 45 degrees. The situation below occurs when four properly-oriented edges are next to each other, ...
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### The First Gate: Why So Tense?

Greetings fellow puzzlers and puzzled alike! I’ve concocted a little puzzle for you all... Well little may be an understatement, but I'll come back to that. Before starting, you should know that the ...
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### Never Completed Game - Difficult Riddle

The seventeenth of the primes. Its twin is twentynine. Po. Let’s drive. Bye, Alfonsín. Add seven triangular. Sweet. It named the Valley. This riddle is taken from https://www.nevercompletedgame....
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### Decrypting the Key

So I've been trying to solve this Riddle called "Phage is Spreading.." ...
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You are participating in a treasure hunt, with the following instructions: X N F I I S + N I G B W P Tired sunrays ...
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### Secret message in a birthday email

A coworker sent this message around on his birthday. Apparently it has a secret message. Here is the exact email body: Good morning FakeCorp, I am turning 25 today so I'm offering loads of ...
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### Alternate, complex potions puzzle from HP fanfic

A long narrow room. The entrance is blocked by purple flame, the path onward blocked by black flame. On a table, the only thing in the room, are two dozen potions in opaque bottles. Half green glass, ...
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### She went… She stayed

In 1969, she went to Kazhakstan. She stayed $1$ year Then she went to Mongolia. She stayed $1$ year In 1971, she went to ...
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### Rethinking this series on the syllabus

I assigned each person in my class the task of creating a number-sequence, however, 4 of the guys I usually consider to be leaders came back with baffling results. Can you make sense of their work ...
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### What is a Richi Word™?

This is in the spirit of the What is a Word/Phrase™ series started by JLee with a special brand of Phrase™ and Word™ puzzles. If a word conforms to a special rule, I call it a Richi Word™. Use the ...