In both Rubicon and Sherlock last week, by bizzare coincidence, the plots involved the use of something called a Book Code (in Rubicon, one of the characters refers to it as "old school"). The method is simple.
Say you want to communicate with someone secretly. You both buy the same copy of a book, To Kill a Mocking Bird, by Harper Lee. It has to be the same edition, identical. You want to send the message "Meet me tomorrow at the station". "Meet" is on page 31, and is the second word on line 33, "me" is on page 183, the fourth word on line 7 (this is not the first occurance), and so on. "Station" doesn't occur in the book, but "stationed" does, page 112, line 5, fourth word. It'll do. You end up with a string of numbers:
31, 2, 33; 183, 4, 7;...
In Sherlock, these are translated into ancient Chinese numerals; in Rubicon, a string of letters by splitting the numbers up into groups that add up to less than 26. In the example:
3, 12, 3, 3, 18, 3, 4, 7, ...
which becomes:
CLCC RCDG...
In Rubicon, the protagonist figures out straight away that the letters represent numbers, probably because of the number of C's, D's etc. The receiver of the code reverses the process. The strength of the code is that without the book, the code is meaningless.
The KGB and GRU (Russian Army Intelligence) used a similar method. They had a purpose designed code book using four figure numbers, so "meet" would have been 5268, "me" 171, and so on. If there was a word that wasn't in the code book, the letters would have specific numbers, "a" 358, "b" 1051, etc. Encoding the example would, again, give a string of numbers:
5268, 171, 5454, ...
The agents had what was called one-time pads. These had random numbers printed on celuloid, which burns very quickly, and which were unique to each agent. These numbers would be added to first string, only being used once, thus the name. If we add the random numbers 8235, 2760, and 6473, modulus 10000 to give us four figure numbers, to the example we get:
3503, 2931, 1927...
These can then be translated into letters as before to make transmitting in Morse easier.
You can also deduce power number using peoples birth dates and translate them into letters to make transmitting into morse.
ReplyDeleteI have to admit, I've found my way here through the Sherlock page. I saw the Sherlock episode last year when it was on the BBC and thoroughly enjoyed it (have recently received the series on DVD - v good christmas present).
ReplyDeleteAlso very much enjoyed this post - it seems you've stripped down to just one post a month recently though, thats a shame!
I was unemployed when I started the blog, but I'm now back in work again. It's a long commute into the big city, leaving me little time or inclination to write, even at weekends.
ReplyDeleteWait !!!!! Do you mean to tell me that there was only to be three of these and that's it !!!! I was ready to settle in for years if incredible television. I was at work here in Manhattan telling everyone about the show and I'd say at least 20% knew of it already; and I'd hazard a guess that that isn't too shabby considering we're across the Atlantic Ocean.
ReplyDeletePlease come to your senses. These actors did a wonderful job bringing the characters of Holmes and Watson to life. Don't let it end!!!
Joe Vega
Rego Park, NY, USA.
What happened to the new Sherlock? Those damn Kiwi hobbits have stolen both our heroes! Waah! Who will keep us safe from Moriarty now?
ReplyDeletePaul Hooper
Jakarta, Indonesia
Fantastic... all of it!! move over Doctor Who's-been... just simply amazing!!!
ReplyDeletecodes and ciphers
ReplyDeletethis stuff is fantastic. the books deduct from
the olden days. but this gives you a chance to
deduct in the real world.