Stack Exchange Network

Stack Exchange network consists of 174 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

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

5
votes
2answers
208 views

Cipher: No idea where to begin [closed]

Ok so I have this cipher which I have no idea what to do with. I have tried most substitution ciphers I know of and still have no idea. Brute forcing with frequency analysis also yielded no results. ...
0
votes
0answers
129 views

Stuck trying to figure out a hidden message

As part of an ongoing "treasure hunt" in an online game that I take part in, there have been several forum posts made in an attempt to hint the participants to finding certain locations. However, ...
3
votes
1answer
182 views

An alternate answer

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

Flipping a coin across the internet

Suppose you wish to "flip a coin across the internet". ie. You want to show other people that you've flipped just ONE coin, and show them the result. I'm currently trying to think of the simplest ...
3
votes
1answer
168 views

Cryptography club

You have been invited to join a secret cryptography society, but you have to decode this message and meet at the location. This is the email you receive: Let's learn your times tables! $5$ X 8 = 74 ...
1
vote
0answers
265 views

I say something. You say “Thanks!”. I say “You're welcome”. What did I say at first?

Work with this: https://pastebin.com/esJCuQAg Clue 1: Clue 2: Clue 3:
5
votes
4answers
488 views

Finding a serial killer

Recently, in the United States, there have been multiple murders all over the country. Because of how similar these murders are, it is believed that a single individual is responsible. There have been ...
1
vote
3answers
136 views

Looking for a place

Seems overwhelming but pretty simple. clue.txt http://junewi.000webhostapp.com/testing/clue.txt tdHCR6ieFHNqUv1zQHE0KRiAfypNTApKi2xlN4CMYK2beP3M1u2mgUvRvDmx0M8heyKebUVEsGcbHrnymUIeviUN/...
9
votes
1answer
337 views

First Cryptography Puzzle

When adam and eve sinned, apple was the key. Lies of the Serpent, they both believed. Alternate: 56 108 87 97 119 53 97 43 57 49 68 105 66 51 121 115 84 54 120 51 81 65 61 61 I'm looking for just ...
0
votes
1answer
77 views

Keybase sponsored this puzzle

Yesterday I found a note under my chair. The note seemed very mysterious so I thought there must be a hidden meaning inside. It read: OJNU OJNU OJNU V YVGRENYYL FGBYR XRLONFR'F PBQR NAQ CBFGRQ VG ...
5
votes
1answer
362 views

Hack of the International Stamped Time Server

The International Stamped Time Server (ISTS) broadcasts a time stamp integrity-protected with an RSA-4096 public key $(n,e)$. But mere days after it starts operation, hackers announce they pwned it by ...
1
vote
0answers
162 views

Decoding ciphertext with base64 yields obscure unicode

Context: I was given a piece of encrypted string to decipher and I have been stuck at it for a while. To not ruin the point of the problem, I will provide only some description of the text and my ...
0
votes
0answers
309 views

Trying to de-code this and I'm having a lot of trouble

The code is: dsetg nvxgn abfus fcaur vvkyq llszs yybik pkefa vbyjj stalk aupoc dvyai qnlrj iewzb qfcct mgqrg xxuqy sapeb reahl btxbz wisfd klbqr letxa zhu I've run it through a bunch of ciphers ...
0
votes
0answers
288 views

What Encoding Algorithm is this? Encode table included

Take the word "puzzle" for example. What this algorithm will do is first break it into pairs: pu zz le Translated using the encoding table: ...
4
votes
1answer
365 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 ...
8
votes
0answers
187 views

Determining the meaning of a challenge coin

I saw this rather cool looking challenge coin the other day, and I was wondering what the associated binary on the back of it means, as it isn't standard ASCII. I'd appreciate it if you all have any ...
4
votes
0answers
164 views

What are these encrypted Starfield tweets saying?

There are a lot of rumors about Bethesda Softworks and/or Bethesda Game Studios announcing a new game at E3 this year, or even on May 14th (source). A key in this mystery is the trademark 'Starfield'. ...
16
votes
1answer
679 views

A lumberjack unjustly captured

One day in China, a lumberjack was caught unknowingly cutting down one of the emperor's favorite type of tree. Because of this, the lumberjack was taken into captivity. The surrounding towns in which ...
2
votes
1answer
293 views

Riley Riddle with a little bit of ciphering

First of the prefix is a hook but I removed one part But it is also locked, and also I forgot the key Just to share with you all, I am eating a salad with a raspberry vinaigrette Second ...
12
votes
1answer
296 views

Imprisoned with a note

Once upon a time, a man was imprisoned by a corrupt leader in a cellar. Every day, a servant would come by and give him a singular piece of bread. One day, he was given a note. On the note, there was ...
10
votes
1answer
677 views

“I like things done once”

You disable the security shields. Dr P releases his minions. Suddenly you hear the red siren. 'Code-Red' says the computer. You smell smoke. You see the background a blur and noises in the air. ...
3
votes
1answer
334 views

How do I solve this Vigenere cipher. Unknown key

I have this cipher text: hrmwnuurseae ucsmnktyqwnc gnheepquvwai uiggmvvofmrp eaikaipoxlog tamkeykmxzev xiplhrvmifdf nizwsrhtijty gmxzexqohasf htmftvtrivwz vhxzeztbsfej uopwtzvbioik jcewsrttlwnf ...
7
votes
1answer
402 views

Mathematicians play hide and seek!

The ghosts of Eratosthenes and Euclid are playing hide and seek. They can hide anywhere in all of space and time, but the pair are in agreement to play somewhere on earth within the years 0 to 2000. ...
9
votes
3answers
339 views

Losing my religion

Cleaning the church in the evening, on one of the seats I've found a strange envelope, which happened to be addressed to me. It was labeled as "Important religious question". Intrigued, I unlocked an ...
4
votes
1answer
217 views

Encrypting with a substitution cipher

I think I went a little overboard, but I made this substitution cipher: MLp;LoyzLpjLhnodLpjLMLjdd;WpfqyoRL;dLhyfL"d!!nolLpoqLzd!!nolL"yvLlfddoLlpfqdojOfdLoyzL4cpzDjLlfy4nolLnoL;"Lej"...
15
votes
6answers
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 ...
11
votes
2answers
552 views

Make some Guacamole!

Subject: Mole Date: Sat, 31 Mar 2018 14:20 From: Chowzen {chowzen@segmented.org} To: PuzzlingEnthusiast {pe@puzzling.se.edu} PE: As you may be aware,I am the leader of an ...
6
votes
0answers
368 views

How to Complete this Cryptographic Challenge?

I've been trying to solve this cryptographic challenge for months: ...
2
votes
1answer
209 views

Cryptography - Decrypt my code

I wrote a new code as my last one seem to fail so badly. I'm doing this by the way, as it's to do with my Mathematics degree. Here's the new code: 141813 61618118, 161415 115 1820181142618 ...
3
votes
1answer
175 views

Cipher that I need help solving

"YB AUVQ DUUACRQ" I've tried every rotation of Cesear and lots of frequency analysis and all I've been able to come up with is "I'm done goodbye". The girl who wrote it says this isn't the answer but ...
10
votes
1answer
282 views

All Bicycle Cards

Well, the last puzzle I made was solved in about an hour, during which time I was busily creating more hints. So this time I'm going to be less forthcoming with the giveaways and see what you ...
11
votes
4answers
730 views

Who destroyed my grandmother's pillow?

The Victim: My favorite pillow. A gift from my grandmother, embroidered with my initials. Ripped open, torn to pieces, soft innards spilled everywhere. The Suspects: Clifford the puppy, Caleb the ...
5
votes
1answer
210 views

Cryptography with painted cells

I really have no idea what is going on in this puzzle, but what I know is that I'm getting cookies for solving this. I thought you might be interested in trying to solve it. Thanks everyone!
6
votes
2answers
394 views

Two mysterious cave notes

Fellow puzzlers! On my vacation to Norway last summer, I've gone on several hikes through the mountains. While the views were absolutely amazing, the hikes also left my with a mystery... On, if I ...
15
votes
1answer
674 views

Code Cracking 1984

This is a code from an old home computer magazine. Still it is unknown the cipher used for it, although they gave the solution: ...
22
votes
3answers
1k views

A half successful police raid

Everything in the next section is flavor text only. You may skip right over it, if you´re impatient. "So, how did it go officer? I hope there was no blunder this time!" The chief commander looks ...
3
votes
1answer
197 views

How do I solve this? I found this on /r/ARG

It says some cryptic wording. I'm unsure how to proceed. Transcription: ...
3
votes
0answers
323 views

Encrypted message (unknown algorithm or plaintext)

I've been redirected here for more, or rather more accurate help from the crypto section of stackexchange. Long story short, we have this assignment that is bugging me. We are supposed to be ...
7
votes
1answer
354 views

Polarizing Encryption: What does it say?

Below is a short paragraph. How would you decrypt this? ...
6
votes
1answer
273 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 ...
4
votes
1answer
259 views

Late 18th/early 19th century numbers grid

I was researching an historical figure on the Isle of Man, Capt George Quayle (b.1751 - d.1835), and in amongst the museum's papers was this numbers grid which was part of his effects. The museum ...
4
votes
2answers
178 views

Is this a known technique or a custom technique?

I recently watched "A Good American," and I'm wondering what the decryption method is that he is using here, or is it a custom decryption method? He slides an array of letters printed on paper over ...
18
votes
1answer
2k views

A Puzzle With the Difficulty Level of Dessert

I have built an encoded message here. Read and ponder. In this particular case I have encoded the name of an American known all over. My method is simple. Don't be fooled. Although this is a short one,...
3
votes
1answer
384 views

What am I trying to say?

This is an enigmatic puzzle. The puzzler must deduce what kind it is and solve it with no help.
4
votes
1answer
215 views

Mysterious Letter

My friend Niko sent me a letter the other day: OP: (The original had errors so the text has been updated) I DONT HΑVE ANY TIME TO TALK. IVE BEEN FRΑMED FOR TREΑSON АND M ON THE RUN. I NEED YOU TO ...
5
votes
0answers
479 views

Need help with a cipher

I am trying to figure out a cipher I think I found in a book from 1982 and it's a 36 year old mystery we are trying to solve (I will reveal the book if this turns out to be something so everyone can ...
6
votes
2answers
452 views

What is the girl's name?

I have just met a girl in a bar, and got her number after some non-sense talk. She gave her number and said that the number after the area code is also her name, and she wants me to call her only if I ...
28
votes
5answers
1k views

The old tinkerer's safe

A client of mine died last Sunday - just as he was born on a Sunday. He was already at rather ripe age, and I had the pleasure to present his last will to his loving and caring family. As far as I ...
6
votes
1answer
296 views

you probably read this wrong!

Read this carefully: ‮114 116 108 111 https://repl.it/010010010100‮11000110110001011000 What's my message? Hint:
7
votes
0answers
381 views

Meteor strikes again

Part of a phone call: -...well why didn't you just say so? -It wasn't as easy as you thought, Jack. All the power lines here were destro--- -I know...It's not like we're living on a different ...