code: def compare_hexdigests( digest1, digest2 ):
      
      # convert to 32-tuple of unsighed two-byte INTs
      digest1 = tuple([int(digest1[i:i+2],16) for i in range(0,63,2)])
      digest2 = tuple([int(digest2[i:i+2],16) for i in range(0,63,2)])
      bits = 0
      for i in range(32):
          bits += POPC[255 & digest1[i] ^ digest2[i]]
      return 128 - bits
docs: Compute difference in bits between digest1 and digest2
         returns -127 to 128; 128 is the same, -127 is different