114 votes

Challenge for lovers

He can't. The commonly-accepted answer was provided by Marius, and looks good on the surface. But consider that Kleptomaniacs are smart. Klep Kleppington III -a particularly wily kleptomaniac- could ...
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  • 2,400
104 votes
Accepted

Challenge for lovers

Solution:
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  • 17.8k
47 votes
Accepted

Break the subsitution cipher with a twist

Scroll to the end if you just want the answer. I give a detailed explanation of how I reached it. First, I hypothesized that the permutation has two cycles: one of length 9, and one length 17. The ...
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  • 23.6k
37 votes
Accepted

Two Sheriffs and Eavesdroppers

Let's say S1 has the list {a,b} and say S2 has {a,c}. S1: {a,b}, {c,d}, {e,f}, {g,h} - one of these is my list. S2: {a,c}, {b,d}, {e,g}, {f,h} - one of these is mine. Now both S1,S2 know their sets ...
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  • 1,668
37 votes

Challenge for lovers

This is just a visual representation of @Marius answer ;)
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  • 3,567
35 votes
Accepted

Go mad with this one-dimensional jigsaw

The answer to this puzzle... We find this by: Doing so results in something that looks like this (in spoiler, below) and the final answer can be read off: A note on my solve path:
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  • 97.3k
34 votes

Two Sheriffs and Eavesdroppers

I think it's pretty obvious. ;) Alternatively,
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23 votes
Accepted

Good Apple Hunting

Why, her name was Explanation: First, what everyone has deduced so far: Then, How do you like them apples?
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  • 3,265
22 votes
Accepted

Descramble the scrambled text

This procedure is called the Burrows-Wheeler transform. It is useful for data compression, because if the starting text contains many identical substrings ("the", "and", ...), then the Burrows-Wheeler ...
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  • 7,678
22 votes
Accepted

A Puzzle With the Difficulty Level of Dessert

The title means We can
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  • 137k
21 votes
Accepted

A letter with no particular backstory

The paper says: How the deciphering works: Now my best explanation of the joke is Here is the paper together with the plaintext:
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  • 5,057
20 votes
Accepted

Message from deep negative space

Let us giving us the quote
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  • 6,826
19 votes
Accepted

Find the secret word in this encrypted image (part 2)

First, I copy-pasted the numbers into Mathematica: str = "181 ... 29"; Next I convert the string to a list of numbers: ...
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  • 15.8k
19 votes

The old tinkerer's safe

It was a pain to solve this, but fun. You can test this with the last diary picture: Now for the real puzzle: Applying the decode algorithm with the correct key gives you:
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  • 5,138
18 votes
Accepted

Murder of a Cryptologist

The answer is: Which is a reference to one of my favourite movies: The first step was to decrypt the text at the bottom of the note using This yields: Next find all of the clues in order. The ...
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  • 13k
18 votes

BFTIODFTTWKBCSC

Solution Key Countries of the participants Reverse-Engineered Ciphering Process Now let's apply this to the original messages. Reverse-Engineered Deciphering Process Reasoning One Last Thing To ...
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18 votes
Accepted

All Bicycle Cards

The decoded message ... First, let's transcribe the card layout, so that we can tackle it more easily: Frequency analysis tells us ... Let's make some assumptions: Let's rearrange the input ...
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  • 48.2k
18 votes

Cracking Nested One-time Pads

Let $+$ and $-$ denote the "standard" arithmetic operations modulo 26 on the English alphabet, done letterwise to strings. Here, encrypting text $T$ with a given one-time pad $P$ is simply ...
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  • 137k
17 votes
Accepted

Multilayer Image Steganography

The final answer is: The clue "listen" pertains to audio files embedded in the images. The legend for the blue layer is four cards. The file is an OGG Opus file. The audio is someone saying "If ...
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  • 13k
17 votes
Accepted

Open the curtains

This is nice! To 'open the curtains' here, we need to: We can then: Doing that produces the following grid: Reading down between my added marks in this diagram reveals the hidden message:
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  • 97.3k
15 votes
Accepted

Find the secret phrase in this encrypted image (part 3)

(No spoiler tags because they're messing with the line breaks...) First we do a trivial reshaping of the image to un-distort it: ...
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  • 15.8k
15 votes
Accepted

For a puzzler such as you, you shall solve with ease

The "P.S." hints that To use that hint, we must
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  • 137k
15 votes
Accepted

A half successful police raid

Thanks to the others here, I managed to figure it out. Sorry about the terrible formatting, I'm pretty new at this. Solution: Explanation: Credits:
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  • 791
15 votes
Accepted

Iceberg Cryptography

I am happy and I know it. The message reads: How is it encoded? The whole story:
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  • 48.2k
15 votes
Accepted

2 Person Same Number Verification

Any commutative hash function will do.  Using RSA makes this relatively easy, I think. So Alice and Beth both establish their secret primes, and, in a twist, keep everything secret.  $ % Make EA, EB, ...
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  • 22.3k
14 votes
Accepted

Matter and antimatter

In a solitude of the great rectangle of pipes, plus signs, and hyphens lies a list of words. They are aligned in a staggered manner along a vertical bar which suggests they should be And so we try ...
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  • 12.6k
13 votes

Two Sheriffs and Eavesdroppers

It's going to be a long phone call. I haven't taken computer security in a while so I hope I got the process right, I was just kinda going off the top of my head.
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  • 930
12 votes
Accepted

Last contact in custody

I think the checkmark should actually go to Lord of dark for actually finding the answer to the original question, but here's the missing bit of the explanation: (Which makes the "no-computers" tag a ...
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12 votes
Accepted

Breaking a systematic password

Updated after the question's correction I think the next valid password is Reasoning: Here is a possible recovery of most of the missing and mistyped characters: I also added if the password seem ...
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  • 9,542

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