Cryptology Warfare: Do or Die

• Suppose that you are a commander of an army during wartime, and your military intelligence has cracked an enemy code that exposes plans to bomb one of your country’s major cities. Tens of thousands of civilians will likely perish if the bombing takes place. However, you also know that if you make a move to add extra defenses to that city, the enemy will conclude that the only way you could only have known that the city was going to be bombed was that you had broken their codes, and so the enemy will change or upgrade their codes as a result, and you will no longer be able to read their communications. What do you think is the best decision to make: Allow the enemy to bomb the city even though civilian casualties will be high, or defend the city even though it means you’ll lose the ability to read enemy transmissions?

Well let’s see… I’m just going to start spitballing my thoughts at the back of this metaphorical kid’s head and see if I can elicit a response from myself, because this is an interesting question. I believe it’s safe to assume both armies have cryptology departments to write and break codes. If my intelligence has broken their code to reveal potentially devastating news, the worst decision to make would be to act brashly, as in immediately fortifying the targeted city. Well, maybe not — it depends on the time of the intercepted message — if the bomb is scheduled to launch relatively soon then yes, my reaction would be the opposite. But if there is time then I would likely do the following:

First, I would request to improve our own encryption methods, likely by means of another layer of either confusion or diffusion. Assuming this takes relatively no time and has little consequences, it will assist in securing the information for what comes next — diffusive fortification. Assuming my army is well equipped to handle such affairs, I would request fortification in a number of cities across my jurisdiction, among them being the targeted city. In Game Theory, I don’t necessarily know what move my opponent will make next, but I must make intelligent guesses as to what his options are, and this in my opinion leaves him wondering or unaware. If he’s unaware, then he will continue with his plan and the bomb will be handled properly by my fortification request. If he is wondering, then he may be suspicious and change his encryption methods or send the bomb regardless.

Looking back at the original question, if I had to give a binary answer, it would be to fortify the city and lose access to their messages. Assuming we both have cryptology teams to write and break codes then this is simply a battle in the war that may never be won, or at least one side may not have complete control over the other for an extended amount of time. It’s a well justified sacrifice, in my opinion, if it means saving the people I have sworn to protect.