The encrypted messages for some stages are in binary form and were therefore given as uuencoded data in the book. This did cause us some problems as this file format is meant to be exchanged by computers, not humans.
In fact, Simon Singh wrongly admitted to an error in one of uuencoded texts. In this case, it had been claimed that the second last line in the file should only contain a back-apostrophe, `. Two out of three messages have a `, but the third one has a blank line as its second last line. This is rather hard to see for the human eye when the text is printed in a book, but a computer would never miss it.
It should be noted that these two characters are equivalent since applying bitwise AND by 63 yields the same results for 32, the index for the space character in ASCII, and 96, the index for the back-apostrophe `. Different versions of uuencode may produce different encodings, but the decoding is still consistent. Since a line always starts off with its length count and length zero means that the file ends, both of these mean end-of-file.