Skip to content

Instantly share code, notes, and snippets.

@albertstill
Last active February 25, 2021 18:46
Show Gist options
  • Save albertstill/426faf8d241d1b255991 to your computer and use it in GitHub Desktop.
Save albertstill/426faf8d241d1b255991 to your computer and use it in GitHub Desktop.
Understand how the Enigma machine works with 30 lines of Ruby
Plugboard = Hash[*('A'..'Z').to_a.sample(20)]
Plugboard.merge!(Plugboard.invert)
Plugboard.default_proc = proc { |_, key| key }
def build_a_rotor
Hash[('A'..'Z').zip(('A'..'Z').to_a.shuffle)]
end
ROTOR_1, ROTOR_2, ROTOR_3 = build_a_rotor, build_a_rotor, build_a_rotor
Reflector = Hash[*('A'..'Z').to_a.shuffle]
Reflector.merge!(Reflector.invert)
def input(string)
rotor_1, rotor_2, rotor_3 = ROTOR_1.dup, ROTOR_2.dup, ROTOR_3.dup
string.chars.each_with_index.map do |char, index|
rotor_1 = rotate_rotor rotor_1
rotor_2 = rotate_rotor rotor_2 if index % 25 == 0
rotor_3 = rotate_rotor rotor_3 if index % 25 * 25 == 0
char = Plugboard[char]
char = rotor_1[char]
char = rotor_2[char]
char = rotor_3[char]
char = Reflector[char]
char = rotor_3.invert[char]
char = rotor_2.invert[char]
char = rotor_1.invert[char]
Plugboard[char]
end.join
end
def rotate_rotor(rotor)
Hash[rotor.map { |k, v| [k == 'Z' ? 'A' : k.next, v] }]
end
plain_text = 'IHAVETAKENMOREOUTOFALCOHOLTHANALCOHOLHASTAKENOUTOFME'
puts "Encrypted '#{plain_text}' to '#{encrypted = input(plain_text)}'"
puts "Decrypted '#{encrypted}' to '#{decrypted = input(encrypted)}'"
puts 'Success!' if plain_text == decrypted
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment