One of the most renowned intelligence officers to use a book code was Richard Sorge, a legendary Soviet spy who operated in Japan. But, more importantly, it solves the issue of passing the key to the counterpart – the parties may agree on using a specific book beforehand. More sophisticated methods are based on the use of the piece of text as a ‘gamma’, or a sequence of characters used to code the message.Īny book cipher allows procurement of an encrypted text not prone to being cracked. The ciphering mechanics are based on a simple principle of a letter being substituted by the number of a page/line/character in the line. As such, it does not seem to be a fictional ciphering system, like the one where you substitute letters with their corresponding sequential numbers.īook ciphers are based on the predisposition that both correspondents have the same book. It is quite easy to refer to the book code, as it’s the easiest encryption method comprehensible enough for the reader. That way you can simply use the Bible for everything.The so-called book cipher has always been in favor with authors of spy novels and detective stories, who usually try to mimic reality but are not ready to feed hardcore tech concepts to readers. It's more secure and more practical to substitute letters rather than words. That would mean looking for a better cipher. If Thomas Beale's house had been searched at the time, the treasure would have probably been easily located as he'd had to have a copy of the Declaration of Independence on his book shelf.Ĭomparatively, imagine if you could recover an AES key by using a side channel to reduce the unknown key space by 99%. And who has 10,000 different books incorporating the word "Wombles"? Searching through either the sender's or recipient's bookshelves would vastly impact security. A long bookshelf with 10,000 books is still only ~13 bits of book choice. So suddenly all books in the world are reduced to not many at all.
There are not many books in the world that contain these exact words, and both message sender and recipient have had to possess one.
"Here we present a model of trabeculation in mice that integrates dynamic endocardial and myocardial cell behaviours and ECM remodelling, and reveal new epistatic relationships between the involved signalling pathways. "Great Uncle Bulgaria – the oldest and wisest of the Wimbledon Wombles and their leader."īut if you're spying on a pharmaceutical company, then your secret message might be:. So if you're reporting on a local colony of wombles, you might encipher and send:. And they have to be word for word, page for page identical. You have to have the book at some point, and so does your cipher text recipient. Whilst you'd think that all the books in the world are at your disposal, in fact they're not. There is a major side channel attack on such ciphers, imaginatively called a premises search attack. * If you're not limited to published books, you might as well exchange call numbers in the Library of Babel, but such a proposition is even less practical. If you need to do this with pen and paper-if somehow you can afford a billion-book library but not a computer-there are probably better pen-and-paper ciphers available, like and. You're better served by using the archaic broken-by-brute-force DES cipher with a 56-bit key than by using this effectively 40-bit key for a book cipher. That makes a trillion possible keys, $10^$-and to write down your cryptosystem, you must literally fill a library. For each book, let's say there's an average of a million words. Cursory research suggests this is an overestimate by a factor of about ten, but let's not quibble details.
* Let's say are approximately a billion distinct published books out there. For this to be a practical cryptosystem with a short key, you're limited to specifying a published book that everyone including the adversary has access to.