Shift Ciphers Challenge

shift_ciphers_challenge.rb

## Here values of secret_offset, secret_key1, secret_key2, plaintext_01, plaintext_02 and plaintext_03 are set

require 'shift_ciphers'  # Library's code at: https://github.com/TeWu/shift-ciphers  (version 1.0.1)

caesar          = ShiftCiphers::Caesar.new(offset: secret_offset)
vigenere        = ShiftCiphers::Vigenere.new(secret_key1)
strong_vigenere = ShiftCiphers::HardenedVigenere.new(secret_key2)

p caesar.encrypt(plaintext_01)  # => "!M;BL;AtKw;MH;ytBEd;uNM;BM;BL;PHKLx;GxOxK;MH;AtOx;MKBxw;MH;LNvvxxwe;1_AxHwHKx;)HHLxOxEM"
p vigenere.encrypt(plaintext_02)  # => "qit$b#D1R-js+ntrt'-7U-hy+bImv-Ehw-Hv/z9$T:l6&qty\".{Go{m1@p"
p strong_vigenere.encrypt(plaintext_03)  # => "cc-9qPhWD>)CB;;cJ%+.q!ZmN(+9es9P!;+7;JqM$38'3}{ioQOyvxovZI9 >"

### The Challenge 
## The challenge is to crack the ciphers and obtain values of plaintext_01, plaintext_02 and plaintext_03

Some help/hints:
https://en.wikipedia.org/wiki/Caesar_cipher#Breaking_the_cipher
https://en.wikipedia.org/wiki/Vigen%C3%A8re_cipher#Cryptanalysis
https://en.wikipedia.org/wiki/Autokey_cipher#Cryptanalysis

Super naïve bruteforce:

require 'shift_ciphers'

N = 5
CIPHERTEXT = "KL*OR@wX;0tf )DYRh0g,0BLwwIR5P7GO;(FjQ8a[WtJ)liF*>Bf"


def for_all_keys(len, &block)
  return if len <= 0
  if len == 1
    ShiftCiphers::Alphabets::DEFAULT.chars.each do |c|
      yield c
    end
  else
    ShiftCiphers::Alphabets::DEFAULT.chars.each do |c|
      for_all_keys(len - 1) do |key|
        yield c + key
      end
    end
  end
end


prev = "";
for_all_keys(N) do |key|
  p key if prev[2] != key[2]
  ShiftCiphers::HardenedVigenere.decrypt(CIPHERTEXT, key)
  prev = key
end

puts "DONE"