Questions tagged [cryptography]

A puzzle concerning techniques for secure communication in the presence of (hostile) third parties.

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46
votes
12answers
10k views

Challenge for lovers

One of my friends gave me this puzzle. Please help me find the answer for it. Jane and Mike have fallen in love, and Mike wishes to send her a ring via mail. Unfortunately they live in Kleptopia ...
32
votes
4answers
2k views

Good Apple Hunting

The boys brought him in for questioning, but I didn't think he had anything to do with this. Not really. I just had to know if he knew anything pertinent about that strange passage in the old man's ...
38
votes
4answers
3k views

Multilayer Image Steganography

Alice, Bob, Carol, and Dan are playing a card game. After they all show their cards, Bob notes that by exchanging two cards the order of the players would be reversed; that is, the player with the ...
32
votes
9answers
4k views

Two Sheriffs and Eavesdroppers

Two sheriffs are working on a case to find one culprit. There were initially 8 suspects; through independent work, each sheriff has narrowed this down to a list of 2. Because they are good sheriffs, ...
19
votes
1answer
1k views

How did my little sister survive?

In a far other universe, my little sister was trapped in a cave. Surprisingly for humans, in this universe, all caves are electronic. This electronic cave had nothing but 5 buttons, two little screens,...
6
votes
2answers
701 views

A Magical Cryptography Puzzle

The following is the first and second sentences of one of my favorite (and fairly popular) fantasy books encoded in a cipher I created a few years ago. I'm quite certain it's breakable, but hints/more ...
19
votes
4answers
1k views

Six Series, Six Words

Update: I've just realized the image had a major flaw in it. I've added a new image and made sure it's correct. Nothing else has changed, only the image. Sorry for the inconvenience. I have six ...
6
votes
3answers
616 views

Two Sheriffs and Eavesdroppers - 2

“The Two Sheriffs” puzzle was already discussed here Two Sheriffs and Eavesdroppers. This puzzle has only one difference: we have seven suspects instead of eight. Two sheriffs in neighboring towns ...
3
votes
1answer
225 views

An alternate answer

Really rare report! Today, Todd texted this: ♦☼ ↓☼§ ♂♫☼↨ ¶◘♣ ☺♫‼○↨♣↕ ♠☼↕ ◄§♣‼¶♥○☼♫ ‼○↑ ☼♫ ¶◘♣ ♪☺¶◘ ◘☼♪♣↨☼♣↕♂? ○ ♥☺♫'¶ ♠○•§↕♣ ○¶ ☼§¶. Although, having solved it, I decided it's too easy and decided ...
7
votes
6answers
741 views

A simple “scientific test…”

I hold every single day, in my lovely picture frame. I look a hundred years old, but I was built on the spot. You might say I'm weak, and I'm four times over the hill. Sometimes I take the elevator ...
5
votes
1answer
422 views

Conspiracy Theories

An entry in Fortnightly Topic Challenge #35: Restricted Title 1. Title based on this xkcd. I think a friend of mine sent me a letter. However, I can't seem to decrypt his message. I'm worried about ...