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.
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How can eight quants learn their average salary without revealing individual salaries? [closed]
Here is a problem from section 2.3 (Thinking Out of the Box) section of the popular book by Xinfeg Zhou titled 'Quant salary':
Quant Salary
Eight quants from different banks are getting together for ...
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Two Sheriffs and Eavesdroppers - 3
“The Two Sheriffs” puzzle was already discussed here. This puzzle has only one difference: we have six suspects instead of eight.
Two sheriffs in neighboring towns are on the track of a killer, in a
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Scheme to select a multiple choice answer on a whiteboard secretly? [closed]
Trying to set up a cute demonstration of cryptography, here's what I'm envisioning so far:
I have a whiteboard, some number of students, and an equal number of different colored markers. On the ...
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The dessert problem (blind ballot remaining blind if non-unanimous) [closed]
A group of (possibly over-polite) people have just finished their meal at a restaurant. One of them asks, "Does anyone want dessert?" The table goes quiet.
Some of the people might want ...
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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), ...
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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
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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How can our secret agent produce a cryptographically secure random number?
Secret Agent Michael Scarn enters his hotel room, only to find it having been ransacked. He needs to send an encrypted message to his handler notifying them that his cover has been compromised.
In ...
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Overhead Projector Cryptography
Back in the day, if you wanted to show an image to a large audience, you would use an overhead projector. This would shine a light through a transparency, which is a clear sheet with a black drawing ...
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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 ...
- 203