Ciphers invented before the era of computers and modern cryptographic theory. Classical ciphers typically operate on letters instead of bits and are usually designed to be implemented by hand or using simple mechanical devices.
5
votes
2answers
800 views
What is the most secure hand cipher?
By "hand cipher", I mean a symmetric cipher for which encryption and decryption can can both be performed with a pencil on graph paper, consuming about 10-20 seconds per character by a proficient ...
0
votes
1answer
318 views
Cryptanalysing Affine cipher
I am trying to cryptanalyse a cipher–text encrypted by Affine cipher.
The encryption formula is: $c = f(x) = (ax+b)\bmod m$, where $a$ and $b$ are unknown constants; $x$ is a plain-text symbol, and ...
4
votes
1answer
547 views
Example of CHI Square test on Caesar Cipher?
I am trying to get my head round the chi square test, when used with the Caesar cipher.
I started off using this formula,
$$ X = \sum_{i = 1}^k \frac{f_i · f'_i}{n · n'} $$
Where ...
