Questions tagged [cryptography]

A puzzle concerning techniques for secure communication in the presence of (hostile) third parties. Do NOT use this for simple "crack the code" problems; use [cipher] instead.

Filter by
Sorted by
Tagged with
33 votes
3 answers
3k views

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: ...
10 votes
4 answers
838 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 ...
6 votes
1 answer
242 views

Follow the randomly-bouncing ball

We are going to generate information out of nothing (well, nothing and a bit of something) just by randomly bouncing a ball. The result will be a message you can use to protect humanity. Let's use ...
18 votes
7 answers
2k views

Cracking Nested One-time Pads

Inspired by the famous "how to send a locked box without pre-shared keys" puzzle, I have designed a Truly Clever and Very Secure cryptographic protocol for situations where you must send a secret ...
39 votes
0 answers
11k views

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 / ...
22 votes
1 answer
1k views

Message from deep negative space

...
6 votes
1 answer
732 views

Impossible foods

Reveal a message by zigzagging down through the rows, selecting one letter per row. Then, start again to find a second message. Then, start again to find a third message. No letter is used in more ...
33 votes
1 answer
3k views

Go mad with this one-dimensional jigsaw

...
14 votes
2 answers
418 views

Matter and antimatter

...
7 votes
0 answers
415 views

A multi-symptom affliction

"Kindly state your name." The nurse's voice was polite, but qiet. "I'm sorry, I can't hear you, my hearing's bad." Being mostly deaf was quite frustrating for our patient. "...
7 votes
2 answers
490 views

Judgment-free construction of a playlist

Alice and Bob are planning a long car trip and need to come up with a playlist for it. For any given song, they have one of four opinions on it: "That's, like, my favorite song ever" (love), ...
9 votes
2 answers
495 views

What is a Tetris 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 Tetris Word™. Use the ...
9 votes
1 answer
586 views

The cryptic college campus killer

You are gathered around the latest victim with your partner. This has been the fourth one this month, and yet you are no closer to solving the mystery. The victim is a history student, apparently lead ...
-1 votes
1 answer
69 views

intercepting the box [duplicate]

If you need to send a message in a box to a person so that no one can intercept it and get the message, how do you do so if you have a padlock and key and they have a padlock and key
12 votes
1 answer
2k views

Crack the pigeon code

Can you crack this message? It was discovered in a chimney in 2012 attached to a carrier pigeon and was most likely sent during the D-day invasions. The GCHQ was not able to crack it, even after ...
21 votes
1 answer
814 views

Open the curtains

Open the curtains to reveal some words of wisdom: ...
6 votes
3 answers
2k views

ᚫᛄ•ᛟᛋᚱ•ᛗᚣᛚᚩᚻ•ᚩᚫ•ᚳᚦᚷᚹ•ᚹᛚᚫ•ᛉ

This is the rune page which has been found on-line in May 2014 released by the mysterious cyber group, Cicada 3301. It consists of cipher text which is the hint to the included hash. Transcript: ᚫᛄ•...
-1 votes
1 answer
85 views

Crypted Gobbledygook, Decrypted Obvious

When it is crypted, it is gobbledygook, when it is decrypted everyone who reads it here understands! zorrqpxj gzu fuebmtvbkexjt gzu baq Happing decoding :)
-1 votes
2 answers
174 views

Really Secure Awesome Cryptography

Really Secure Awesome Cryptography is a protocol for sending messages based on public-key cryptography. Assume that messages are simple text strings of at most 500 characters. Users choose a private ...
1 vote
1 answer
141 views

Break into Goldbach's safe

You need to unlock a safe by typing in the correct password. All you have is the following note: ...
5 votes
1 answer
438 views

Can you crack this multiple-shift cipher?

The below is the cipher that is to be cracked : ...
0 votes
2 answers
573 views

binary to be decoded (HARDER)

Below is binary but its translated from something else i dont think a binary to text editor would work 00110001 00110010 00110100 00100000 00110001 00110101 00110000 00100000 00110001 00110101 ...
0 votes
1 answer
166 views

Can you crack this mod of the Caesar cipher?

I want to know how secure/insecure my implementation of the Caesar cipher is... Ciphertext to decrypt : ...
6 votes
1 answer
199 views

Audio Steganography

A simple question, without a simple answer. Rome would be the obvious answer, but it is not THE answer. A picture contains a 1000 words, this audio contains one. https://youtu.be/HiH4_A0xq40 If you ...
4 votes
1 answer
250 views

Great Caesar's ghost, I smell Bacon

This should be relatively simple for you guys. Spaces and punctuation do not count towards the answer. It's a quote from a character in a TV Show, but that has nothing to do with what the answer is. ...
7 votes
0 answers
335 views

Can you crack my cipher?

Can you crack this cipher of mine? Each 6×6 box is a word; therefore there are 26 words. All words are English. The text is read left to right, top to bottom. As might be guessed, the 36 squares per 6×...
48 votes
12 answers
11k 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 ...
4 votes
1 answer
209 views

Cryptography puzzle

The two strings below describe the same English word: 7415963852 1475369963 What word is it? Just for fun! Credits: Hindemburg Melão Jr.
16 votes
1 answer
1k views

What is the Color Code™?

Inspired from Can you name the country code? and What is a Number™? series $ \begin{gather} % custom template - reuse if you may \def\S#1#2{\Space{#1}{21px}{#2px}}\def\P#1{\V{#1em}}\def\V#1{\S{#1}{9}}...
8 votes
1 answer
415 views

The Cardboard Box Cipher

Here's a one-step monoalphabetic substitution cipher that I originally posted on CodeAWeek. (Link in my profile.) The key to solving it lies within the following poem: A clerk gave me a cardboard box ...
5 votes
4 answers
2k views

Scrambler puzzle (CTF forensics problem by me!)

Before anyone starts hyperventilating, this is not part of an ongoing CTF! I just made this example CTF problem for fun... To learn more about what a CTF is, check out this Wikipedia page. For this ...
7 votes
1 answer
423 views

Why did she choose O6G?

He gave her 8 choices. 7 lead to death, one lets her continue. O6A O6B I6C U6D I6E I6F O6G O6H Of course, he knew she had no idea. He turned the hour glass and gave her 5 items from his suitcase....
5 votes
1 answer
251 views

Missing elements of this 32-length list

The following list has 32 elements. Element 8 and elements 22 to 32 are missing. Can you find why element 8 has been chosen to be missing? And can you find what are the missing elements? RTKW EHKB ...
39 votes
4 answers
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 ...
10 votes
1 answer
357 views

Hopscotch Cryptograph

With a little squinting, you should be able to discern a message which runs from the top to the bottom of the text box below. (I have indicated the column with a little arrow.) That is the visible ...
1 vote
0 answers
220 views

What are sequences of letters/symbols for creating a cipher?

I have two gears with different numbers of teeth (20 and 10): The small gear makes two turnovers, while the large gear makes one turnover only. My idea is to use a large gear as an alphabet wheel (...
2 votes
0 answers
333 views

Know the right method, get your share

You took part in a bank heist and wait for your share. Finally this message comes in: ...
21 votes
0 answers
2k views

Decrypting the Key

So I've been trying to solve this Riddle called "Phage is Spreading.." ...
13 votes
12 answers
2k views

2 Person Same Number Verification

Alice and Beth both receive a random integer from 1 through 10, inclusive. They only know the number that they are given. The two of them want to come up with an algorithm to check that their ...
30 votes
1 answer
607 views

Iceberg Cryptography

See if you can extract the message encrypted in this text box: ...
4 votes
0 answers
219 views

%#@& : $!*^ :: SOFT : 5697 :: 8924 :?

If %#@& is coded as $!*^ and SOFT is coded as 5697. ...
11 votes
2 answers
506 views

A puzzling nature walk

While wandering through the forest Taking lots of snaps I found a mossy clearing Where my pup could take a nap I glanced around the bushes I heard a rustling sound And there I spied a crumpled note ...
27 votes
1 answer
2k views

BFTIODFTTWKBCSC

This is my first self-developed cryptographic puzzle. I hope it is neither too hard nor too easy for you to break, and that you enjoy it. Please do not only post the answer, but also your way towards ...
2 votes
0 answers
261 views

I Need Help Solving A Riddle - Its Just An Image?

So I was in this hackathon competition where they promised the people who placed in the top 3 a lot of money and then they delayed the results two weeks. Yesterday, when they were supposed to announce ...
4 votes
1 answer
213 views

I wrote you a message

Take the dogs out for Millan, but only after you find the alphas. dog 1234 Ny nx dog 556 fqrtxy Fzlzxy 567 dog 5819 gzy 2 nx 345 dog 13445 fqwjfid 74859 mty. 55645788 dog 1234 Xyfd 5678 kwtxyd! ...
3 votes
1 answer
189 views

Saturdays' Sequences

0.469281 0.267974 0.333333 0.333333 0.666667 0.499346 0.333333 2 2 1 1 2 2 1 3 2 F 0 0 0 0 U P F O X F E 0 0 1 1 2 1 1 Here are 5 intertwined sequences. I will add one sequence each saturday ...
6 votes
1 answer
196 views

A world with roman numeral alphabet

Tomorrow you will wake up and all the letters will be replaced by roman numbers. That'll be "ok" when you'll learn the replacement's order! Nevertheless, today you have the possibility to make it a ...
19 votes
1 answer
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,...
2 votes
1 answer
167 views

Help with an image I'm assuming is cryptic

Got sent this on Discord, and I need help with identifying if it's like anything secretive or etc. If anyone can help that'd be thankful (Edit) Here's a zoomed version of that string: "...
5 votes
2 answers
348 views

SAD!!!...System Access Denied..you got three minutes to input three digit passcode

Given Hexagon is super secret system with varying levels of access. Users do not have to remember any password. They just have to answer the questions posed by Hexagon strictly in the allotted time. ...