Příklady: ruby main.rb encrypt input.txt output.txt keys.txt, ruby main.rb decrypt output.txt result.txt keys.txt

Encryptor.rb

class Encryptor
	def self.encrypt(string, raw_key)
		key = normalize_key(raw_key, string.length)

		buf = []
		string.length.times do |i|
			char_code = (string[i] + key[i])
			char_code -= 256 while char_code > 255
			buf[i] = char_code.chr
		end

		return buf.to_s
	end

	def self.decrypt(string, raw_key)
		key = normalize_key(raw_key, string.length)

		buf = []
		string.length.times do |i|
			char_code = (string[i] - key[i])
			char_code += 256 while char_code < 0
			buf[i] = char_code.chr
		end

		return buf.to_s
	end

	private

	def self.normalize_key(key, length)
		key * (length / key.length) + key[0, length % key.length]
	end
end

input.txt

Frantisku, uz te nepotesi,
2
ze Francouz jsi a ze vsi zdejsi;
1
ted na krk opratku ti vesi;
4
at pozna, oc je zadek tezsi.
2

keys.txt

jednorozec
Unicorn
Meda Beda
nbusr123
heslo_je_veslo

main.rb

require 'Encryptor'

raise '4 parameters expected: mode input_file output_file keys_file' if ARGV.count != 4

mode = ARGV[0]
input_file = ARGV[1]
output_file = ARGV[2]
keys_file = ARGV[3]

raise 'Invalid mode, one of encrypt/decrypt expected' if !['encrypt', 'decrypt'].include?(mode)
raise 'Input file not found' if !File.exist?(input_file)
raise 'Keys file not found' if !File.exist?(keys_file)

keys = []
File.open(keys_file, 'r') do |file|
	i = 1
	file.each_line do |line|
		keys[i] = line
		i += 1
	end
end

File.open(input_file, 'r') do |file_i|
	File.open(output_file, 'w') do |file_o|
		buffer = []
		file_i.each_line do |line|
			buffer << line
		end

		for i in ((0..(buffer.size / 2 - 1)).map {|j| j*2})
			key = keys[buffer[i+1].to_i]
			if (key.nil?)
				puts 'Nelze ' + (mode == 'encrypt' ? 'zasifrovat' : 'desifrovat') + ' zpravu "' + buffer[i] + '", protoze poradi klice (' + buffer[i+1] + ') neni platne'
				next
			end
			result = mode == 'encrypt' ? Encryptor::encrypt(buffer[i].strip, key.strip) : Encryptor::decrypt(buffer[i].strip, key.strip)
			file_o.puts result
			file_o.puts buffer[i+1]
		end
	end
end

No jo, ruby… To je tak když ho máme ve škole, jinak bych se asi neodvážil. :P