text: #!/usr/bin/python3
  
  # Fixed XOR
  # 
  # Write a function that takes two equal-length buffers and produces their XOR
  # combination.
  # 
  # If your function works properly, then when you feed it the string:
  # 
  # 1c0111001f010100061a024b53535009181c
  # 
  # ... after hex decoding, and when XOR'd against:
  # 
  # 686974207468652062756c6c277320657965
  # 
  # ... should produce:
  # 
  # 746865206b696420646f6e277420706c6179
  
  def xor_strings(b1, b2):
      """XOR two strings"""
      if len(b1) != len(b2):
          raise ValueError('Two strings not of equal length')
      return bytes([a ^ b for a,b in zip(b1, b2)])
  
  
  if __name__ == "__main__":
      print('Set 1: Challenge 2: The kid don''t play')
      s1 = bytes.fromhex('1c0111001f010100061a024b53535009181c')
      s2 = bytes.fromhex('686974207468652062756c6c277320657965')
      print(xor_strings(s1, s2) == bytes.fromhex('746865206b696420646f6e277420706c6179'))