require 'base64'

def str(bytes)
  bytes.pack('C*')
end

def xor_buffer_with_bytes(buffer, bytes)
  result = Array.new(buffer.size)
  result.each_index do |i|
    byte = bytes[i % bytes.length]
    result[i] = buffer[i] ^ byte
  end
  result
end

ciphertext = Base64.decode64('ptITlnk7EGRodZ/dRp9dF1VqaEOPjC2SMQdUYGgmn81GhzEqVHsEX6brBqRwMBEySgo=').bytes
crib = ARGV[0].bytes
key_size = 10
max_offset = ciphertext.length - crib.length
(0..max_offset).each do |i|
  key = Array.new(key_size, 0)
  crib.length.times { |j| key[(i+j)%key_size] = ciphertext[i+j] ^ crib[j] }
  p str(xor_buffer_with_bytes(ciphertext, key))
end