This project encrypts & decrypts a modified version of the Caesar cipher. It also implements a rudimentary, naive cracking algorithm to crack Caesar ciphers using an English dictionary.
For keys under 26, the encryption algorithm is a typical Caesar cipher shift
algorithm, otherwise known as ROT n. Each letter in each word is shifted by
key positions, so if the key is 1, a becomes b, y becomes z and z
becomes a.
For Example:
$ echo "abc xyz"| bin/caesar encrypt --key 1
bcd yza
For keys over 25, the key is converted into base 25 and we get an array of shift values. For example, a key of 27 converts to offsets (1,2). This would offset the first char by 1, second char by 2, third char by 3, etc. Unknown characters are skipped.
For example:
$ bin/caesar offset --key 27
Key: 27 [1 2]
$ echo "abc xyz" | bin/caesar encrypt --key 27
bdd zzb
The project includes a rudimentary cracking algorithm that iterates through keys
and if a certain percentage of the words in the decrypted text are included in
the dictionary (wordlist.txt), the text is considered decrypted.
$ bin/caesar encrypt --key 1234 < text.txt | bin/caesar crack --max-attempts 10000 --parallelism 4 --percent-words 30
Key: 1234 [1 24 9]
Message:
the action of a caesar cipher is to replace each plaintext letter with a different one a fixed number of places down the alphabet. the cipher illustrated here uses a left shift of three, so that (for example) each occurrence of e in the plaintext becomes b in the ciphertext.
in cryptography, a caesar cipher, also known as caesar's cipher, the shift cipher, caesar's code or caesar shift, is one of the simplest and most widely known encryption techniques. it is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. for example, with a left shift of 3, d would be replaced by a, e would become b, and so on. the method is named after julius caesar, who used it in his private correspondence.[1]
the encryption step performed by a caesar cipher is often incorporated as part of more complex schemes, such as the vigenère cipher, and still has modern application in the rot13 system. as with all single-alphabet substitution ciphers, the caesar cipher is easily broken and in modern practice offers essentially no communication security.
Run make build. This will create bin/caesar