Questions tagged [cryptography]
For challenges involving cryptography, including things like ciphers and hashing algorithms
63 questions
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Shortest possible valid PEM-encoded CA certificate
The challenge is to create the shortest possible PEM-encoded CA certificate. The PEM format is specified in rfc7468 (section 5.1 shows an example certificate), and the structure of certificate data (X....
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Produce a secure block cipher round function (1 bit round key; 7 bit message) [closed]
We need to produce a block cipher round function with a 1 bit round key size and a 7 bit message size with the highest level of cryptographic security according to our measure of security.
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Encrypt AES256 (ECB Cipher Mode)
I've looked and could not find a post for this, if there is one, I'll remove it quick! Related and also related
The goal is (hopefully) clear: create the shortest code (in bytes) that implements the ...
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1
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MD5 Hello, World!
MD5 checksums are relatively easy to crack. For this challenge you will create two separate programs, the first one writing Hello, World! and the second one writing ...
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12
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just a caesar cipher... with a twist [closed]
I have been going to puzzling.se, and people over there write stuff in rot13 a lot, sot this gave me an idea:
Write a program that takes 2 inputs, a string and integer:
the message to encode or ...
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Russian Caesar cipher
The objective
Given a Russian text, encrypt it with Caesar cipher with key 16.
The basic Cyrillic alphabets
The basic Cyrillic alphabets are: (U+0410 – U+042F)
...
107
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12
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Proving that a Russian cryptographic standard is too structured
The aim of this challenge is to find an impossibly short
implementation of the following function p, in the langage of your
choosing. Here is C code implementing it ...
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11
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Convert alphanumeric (base-36) sentences into hexadecimal (base-16) sentences
I use "sentence" here loosely to mean "any sequence of words separated by spaces" and "words" to mean "sequences of alphanumeric (hexatrigesimal) characters unseparated by spaces".
Conversion is from ...
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3
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Generate an RSA key pair
Given a positive integer \$N >= 4\,ドル output an RSA key pair (both the private and the public key) whose key length is \$N\$ bits.
The RSA key generation algorithm is as follows:
Choose an \$N\$-...
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user45941
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6
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Gimli, make it even shorter?
I'm one of the authors of Gimli. We already have a 2-tweet (280 chars) version in C but I would like to see how small it can get.
Gimli (paper,website) is a high speed with high security level ...
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9
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911
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Shifting Caesars Shifts
Description
A Caesar Shift is a very simple monoalphabetic cipher where each letter gets replaced by the one after it in the alphabet. Example:
...
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3
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Straddling Checkerboard Cipher
The Straddling Checkerboard is a method for converting letters to numbers and was part of a pencil an paper cipher known as VIC
To convert letters to numbers first you have to make a checkboard like ...
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9
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Decode the hidden message!
Introduction
One day, you were just relaxing in your office in the CIA, when suddenly you see an alert on your computer. Your programs have just intercepted hundreds of coded messages! A quick ...
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6
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Shh... Can You Split a Secret?
In Applied Cryptography by Bruce Schneier (which I have been reading quite a lot recently), a protocol for splitting secrets is discussed. Here is a brief description:
Trent generates a random ...
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Generate a cipher
Generate a cipher given a number and string
Your task is simple. Given a string s and a number 0 <= n <= 9 as inputs, ...