I heard this method of creating a code described in a movie a long time ago. Two people want to send encoded messages to each other by mail(or now email). To encode their messages they both buy the same novel , lets say Moby Dick. To write the message they use a system where a triple set of numbers designates a letter. For example(240,15,41) means on page 240 of Moby Dick on line 15 of that page and position 41 of that line is the letter that the person wants to use to spell out a word. This system is good because a different set of triple numbers can be used to stand for the same letter, i.e. the letter k can be (17,6,43) or(88,51,7) so you can't use frequency to determine the letter. Also the space between words can also be represented by a set of triples, so the encoded message has no separate words and you don't know the word length of any word. The whole encoded message would be a chain of triples like (56,45,3)(316,44,53).... for the whole page. As long as the code-breaking novel, Moby Dick, is kept a secret, is this code unbreakable?