In his office at Bletchley, Turing sipped on his tea, and winced. Rationing was making even the smallest pleasures of life almost intolerable. Between the small quantities of poor-quality tea, the measly portion of milk the ration board allowed, and the total unavailability of lemons, it was becoming almost impossible to make a drinkable cup.
He stared at it, half wondering if someone had replaced his drink with old dishwater. Certainly the colour and taste were similar – the greyish liquid in the cup bore little resemblance to anything he would have thought of as tea before the war – but there was a metallic greasiness to it that could only come from a military institutional tea urn. No, this was his tea all right, more’s the pity.
There was nothing for it. He would have to drink the foul muck. He needed the refreshment in order to get to work, and he was working on what seemed to be an insoluble problem. He took a large gulp – better to get it over with. There was nothing to savour in that cup.
He remembered how tea had once been an actual pleasure. One of the few in which a man could indulge without guilt, without worry for his health, and without even the risk of disgrace or imprisonment. Tea, mathematics, and running, and little else, had made life worth living. Now he had no time for running, and the tea was undrinkable. But at least he had an actual intellectual problem to sink his teeth into again.
He looked again at the documents he’d been given. The fact that they had been brought into the country by Hess was, of course, important, but more important from Turing’s perspective was the fact that these documents were not a standard German cipher. None of them made any sense at all, and without some kind of crib or idea of what was in them, it was useless to even try decrypting them – but that was precisely why they were such an interesting challenge; the first really good one Turing had had in months.
“I’ve tried a few techniques – basic frequency analysis, that sort of thing – in case it’s a simple substitution cipher or something of the sort. It isn’t, but it may be as simple as two plaintexts summed together. When I try these things, I get little fragments of sense, but it quickly turns into gibberish again.”
He knew he had to stop talking to himself – walls had ears, and careless talk cost lives, and all the other homilies that were included on the garish coloured posters plastered over every vertical surface everywhere one looked these days – but it was a habit that was hard to break, and sometimes one needed an intelligent conversation.
It definitely wasn’t the Enigma code, that much he knew. They’d broken the codes for every day up to Hess’ arrival, and every day since for that matter. It didn’t match any of them. Anyway, they wouldn’t have allowed an Enigma to be brought into the country. Too dangerous. It had to be some sort of pen-and-paper cipher.
But what? It didn’t seem likely to be a one-time pad – as far as he knew, the Germans never used them. Too risky, when they had a crypto system they could use instead, and which as far as the Germans knew was unbreakable. But if it wasn’t Enigma, or any of the lesser systems they used, that seemed to leave only some system that only Hess himself knew. And of course, Hess wasn’t talking.
Turing knew that the solution must be obvious – pen-and-paper codes had not really advanced much since the time of Julius Caesar, and any schoolboy could, with sufficient ingenuity, break one. The problem was that “sufficient ingenuity” could in this case mean days or weeks of work, and if the information was about some new German battle-plan, he may not have the time.
Was it keyed to some book? If so, it would have to be one easily available in Britain, and in an edition to which Hess had had access while still in Germany.
He looked again at the sheets. He’d made clean, typewritten, copies of the documents, which had originally been in Hess’ almost-unreadable handwriting. He had, of course, first made sure that there was nothing about the documents themselves that may be of use, but there was no sign of any steganographic system being used. No letters were out of place, no unusual spacing, no pin-pricks above important letters. Just page after page of gibberish.
He finished the drink, and chained his mug back to the radiator, pocketing the key once again. Ridiculous that in a top-security environment, where decisions that would affect the fate of the nation were made and where everyone was trusted to keep secrets which, if revealed, could lead to the very destruction of the Empire itself, he had to keep his tea mug chained up in case of theft.
It just went to show, he supposed, that people’s behaviour in the public and private spheres was different, as if people wore different masks for different occasions, and it was impossible to judge what, if anything, was happening in the brains behind those masks.
But at least with people you had clues – not just their words, but their tone of voice, their body language, their facial expressions. You could watch and listen to those clues, and with enough work you could figure out what was going on inside their heads. You’d never be able to decrypt it perfectly, of course – there simply wasn’t enough data leakage for that – but you could get a good enough idea. You had something to go on.
But if one could work out people’s motives from their actions, surely it must be possible to work out the much simpler puzzle of what Hess’ text contained, given the much larger amount of data available? Looked at that way, the task before him was almost trivial. He could do it. He knew he could.
He got back to work.
This is an excerpt from my novel, Destroyer. If you like this chapter, please buy the book. It can be bought in hardback from Lulu. The Kindle and paperback editions are available from Amazon (UK) and (US). For non-Kindle ebook versions This Books2Read Universal Link will give you links for your preferred ebook retailer.