Fun Fact of the Day: Book Code




(posted by Kristycat)

A book code is an old way of sending secret messages.  See, normally to send a secret message, you need either a cipher or a codebook – but ciphers can be broken, and codebooks can be stolen (and are pretty incriminating anyway – a bad thing to be caught with if you’re a spy!)

So instead, you use a regular book – something innocuous, that both you and the person receiving the message could own without it looking strange and suspicious.  Traditionally, you would use either a dictionary (because it has just about all the words you could realistically need) or a Bible (because for large swaths of history in certain parts of the world, just about everyone could be expected to own one), but really as long as the book is big enough to have a good selection of words and as long as you and your friend both have the same edition, you could use anything!

The basic version is this: write down the page number on which the word is found, then write down the number showing which word on the page it is.  So if you want to write “Hello,” you’d find a page with the word “hello” on it – let’s say page 53 – and then count the words on the page.  If “hello” is the 32nd word on the page, you would start your secret message with “53 32” – “Hello!”

At that point of course you can ALSO employ codes and ciphers and layers upon layers of encryption, but it’s a decent little code just to start with.

This has been your fun fact of the day!  Go forth and send secret messages!


4 thoughts on “Fun Fact of the Day: Book Code

  1. Firedrake March 9, 2014 at 12:33 pm

    Agreeing on a book, of course, has to be done in secret, and may in itself be suspicious activity. Sending messages consisting of numbers certainly attracts attention. I fear that modern analytical techniques have relegated this to “fun” rather than “potentially useful”.

    That said, if you’re already under suspicion, it’s a decent system if the book is one that you have anyway and consult frequently. (The most opened book is obviously going to get checked.)

    For a book with large pages, page/line/word may be better than page/word.

  2. anamardoll March 9, 2014 at 1:51 pm

    I actually know this one from the Red Dragon book by Thomas Harris. There’s a letter which goes:

    I offer 100 prayers for your safety.
    Find help in John 6:22, 8:16, 9:1; Luke 1:7, 3:1; Galatians 6:11, 15:2; Acts 3:3; Revelation 18:7; Jonah 6:8 . . .

    The police have to decide whether to let the code through before they decode it or not. And (spoilers!) it ends up containing the home address of a proposed next victim. Whoops!

  3. storiteller March 9, 2014 at 7:23 pm

    Spoilers for Sherlock!


    One of the cases uses this code in Sherlock, but they use the A-Z Maps book for London, which I thought was a nice update of the Bible being the ubiquitous book.

  4. christhecynic March 10, 2014 at 10:02 am

    I have internet… for about an hour. Follow up visit on the concussion tonight and other than feeling completely hopeless about everything, things are going ok. My computer I don’t know about because, by default, updates go to my mother’s email address. Can’t check my personal email anyway. Just school email.

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