Page 79: Windtalkers

Here is a timely article on the Windtalkers (referred to here as Code Talkers):

http://news.yahoo.com/s/ap/20091110/ap_on_re_us/us_navajo_code_talkers

Windtalkers, as is discussed in the article, are Navajo tribesmen who served as living Enigma machines, coding and decoding messages spoken over the radio in "real time" for American soldiers in World War II.  They performed this valuable service simply by speaking to each other in their rare and unwritten language. A rare and unwritten language is an unbreakable code -- unless you get someone who speaks the language, then it's easy.

As Hannah learns in Old Blood, breaking codes is an exercise in both linguistics and mathematics. Simon Singh's book The Code Book lays it all out perfectly, but I will attempt to convey the gist below.

The oldest codes are called "substitution cyphers" and consist of taking one letter or word and substituting it with another. If all j's are made k's and all o's made into p's, etc., my name would be kpio. These codes can be very useful, but are vulnerable to the limitations placed by the character set of the base language. Simply put, English uses a lot of e's. So, if confronted with a substitution code, you count up all the letters used. The most common one is probably e. There are frequency tables that help you guess what letter has been substituted for what. It's really just a matter of counting, then trying combinations until you get something readable. The perfect job for a computer.

Regarding the Windtalkers, because Navajo was an unwritten language, there was no character set, so no amount of substitution fiddling could crack the code.

Stronger codes use more complex modes of substitution that defy character analysis, but the weakness of all codes is that they ultimately say something comprehensible. The simplest way to crack a stronger code is to figure out what a message must be saying and work backwards. Nazis in World War II would radio the weather report to their U-boats. This practice had the double-weakness of being logical and being repetitive. If it was a sunny day all over the Atlantic, then that string of numbers or letters that was in every message sent out that day probably meant "sunny". From that linguistic insight the mathematics take over. If one is able to figure out how the code for "sunny" was derived, then it is possible to unravel an entire code and unveil more important matters.

That's why the more colorful practice of code names came about. It wouldn't matter if the allies figured out that messages were repeating the word "Barbarossa", because even if they cracked the code they would still have no idea what "Barbarossa" meant. Take it a step further and create a nonsense word that means something important. "XlFlip3fj" is a great code word because, even if a computer decoded it, it might not know it decoded it. This is why password protected websites want you to choose words that aren't in the dictionary, it denies the codebreaker an "aha" moment.

Which brings us back around to the Windtalkers: The only threat to the Navajo code was the weather-report method discussed above. The trick with the Windtalkers was to come up with Navajo words or phrases for the key things they needed to talk about that didn't repeat all the time. The Windtalkers cleverly came up with descriptions for things like the word "bomber" that conveyed the meaning without becoming repetitive. Linguistics ultimately trumped math: "Bird of destruction", "bringer of explosives", "death from the sky", etc. all describe the bomber without becoming a code giveaway. Without a Windtalker of their own, the Japanese had no chance of knowing what the Americans were planning.

In Old Blood, the detectives face an unknown character set written in an unknown language on an unknown subject. There's nothing there to work with. They need a Windtalker.