Turing’s Machine 215

Turing’s Machine 215 The advantage of this cipher is that I can easily remember the name George. I don’t need to write it down. And the circular application makes the message sufficiently obscure you cantt easily work it out... Is this, therefore, a good code? No. This cipher is easy to break. Once you have guessed that I have applied a repeated short code word, you can write out ALL the possibilities and decrypt my message! This may be tedious, but if you are fighting a war and your life depends on it, you can employ a thousand people to write them all out. The British government employed 10,000 people at Bletchley Park, many of them doing exactly this. You might think that applying ALL the possibilities is too time consuming in practice but there are many shortcuts. If I suspect the message contains the name of a German town all I need do is try keys until I find a German town somewhere in the message then work my way outwards from there. Or perhaps I suspect the key is something easy to remember like the name of the Commandant’s dog. I can try ALL German dog names until I get lucky. If I’ve 10,000 people working for me this is easy. The Enigma machine and the coding process set up to operate it was designed to remove these loopholes. For a start, the keys were all random numbers taken from a code book — no dog names allowed — and the machine took the idea of a simple progressive cipher and made it much more complex. Imagine I took my GeorgeGeorgeGeorge pattern but then every 3" character added one, every 14" character subtracted 15 and every 40" character added the 3™ letter of the First Mate’s mother’s maiden name. Now this would be a VERY hard code to break. I would need a machine to code messages because if I tried to do it by hand I would make so many mistakes that the messages I send would be unintelligible. The Enigma machine made these coding schemes a practical possibility. But, although Enigma is hard to break it is not impossible with enough computing power. Is there any code that is impossible to break? An Unbreakable code Is there a way of coding a message so you can never break it? The answer is there are two ways to code a message so it is PERFECTLY safe. The first is to use a one-time pad and the second is quantum cryptography. HOUSE_OVERSIGHT_015905