Episode 27: A Cipher Not a Code

Season 1: The World Unseen

It was warm, very warm. Kiran felt his chest and abdomen rising and falling. He was breathing. It was too warm. Blankets under his chin. Itchy. He moved an arm, then a hand, and pushed them back.

Voices.

‘Is he stirring?’

‘Yes, I think so.’

Kiran opened his eyes. Shapes and colours, dull and formless. Nothing certain.

Then a darker shape loomed across his field of vision. He shrank from it.

‘There, there, old chap. You’ve had quite a turn.’

A hand on his shoulder, a gentle squeeze.

Kiran blinked rapidly, tried to focus, to remember.

The last voice was Major Lock’s. He remembered something now. They were sitting at a table, eating and talking. And then he blacked out. It was humiliating. He hoped he had upset nothing on the table, or embarrassed himself…

He remembered a man in his neighbourhood back home. The man had been prone to seizures and blackouts. And when it happened, he wet himself. Sometimes he even —

‘Can you speak to us?’ Lock said.

‘Better let him rest a bit longer, Major.’ And that was Sergeant Draper. They were coming into focus now.

Kiran spoke, and it felt as if he hadn’t spoken for a very long time, as if he had lost the power of speech and only just regained it.

‘I — I think I’m alright, gentlemen.’

‘Are you sure, lad?’

Sergeant Draper. Kind man, cooked me a delicious meal, sounds concerned now. But I’m —

‘Alright, sir. Really, I am. But very thirsty.’

Draper went downstairs to arrange some tea.

Twenty minutes later, Kiran was sitting up in bed, sipping sweet tea, and feeling much more cheerful.

’So you gentlemen carried me up here to Major Lock’s bedroom? I hope I wasn’t too heavy for you.’

‘Have no fear, Mr Nambudiri. You were as light a feather,’ Draper said.

‘Have you ever blacked out like this before?’ Lock said.

’Never in my life,’ Kiran said vehemently. ‘Gentlemen, you must be honest with me. Did I do anything — When I lost control of myself, did I —’

Lock shook his head. ‘You fainted, but Draper caught you before your face fell onto your food. No mess, nothing like that.’

‘That’s a relief,’ Kiran said. ‘But how long have I been unconscious for?’

‘Oh, about three hours,’ Lock said casually.

‘Three hours!’

‘I had a doctor come and examine you. He couldn’t find anything physically amiss and told us to let you sleep.’

Kiran tried to remember the moments before it happened. That feeling. Something he had never felt before. As if he wasn’t alone in his own mind. The memory of it disturbed him.

‘Can you remember anything about it?’ Lock said.

Kiran frowned. ‘Only that I had a very peculiar feeling. As if someone was observing me. But from the inside.’

‘From the inside?’ Lock said.

‘Yes, I know it sounds strange, but that’s what it felt like.’

One moment he had been discussing Dr Henry Lock’s notebooks and the next he had felt this intrusion. But who or what had intruded? Was it some instance of the Divine who had suddenly taken an interest in the callow mind of Kiran Nambudiri? Or one of its messengers? And yet Kiran couldn’t remember a message.

Had he blacked out before the message could be delivered? That would be extremely disappointing. Besides, he felt that the Divine, knowing him as It must, would speak to him in the language of mathematics. And It would surely have prevented him from fainting.

The more he recollected, the more he felt there was nothing divine about the intrusion. It was mundane, it was furtive. It was more like a thief entering a house. He couldn’t explain how he knew this. But he knew.

‘May I have look at one of the notebooks now, Major? i need to exercise my mind for a few minutes. It will help to revive me.’

Lock went to the bureau on the other side of the room and returned with a slim notebook bound in black leather.

He opened it and pointed to one of the pages. ‘Here’s an example of the code.’

Kiran considered the letters for a few minutes, then closed the notebook and handed it back to Lock.

‘I must get back to my lodgings or Mr Smiggins will think I’ve deserted him.’

He eased himself out of the bed.

‘I’ll go with you,’ Lock said.

It was a short walk back to the lodging house, through silent, empty streets. The air was cool, with barely any breeze. Kiran looked up at the stars hanging in the blackness and felt a sudden pang of homesickness.

‘We didn’t get the chance to finish our conversation after that unfortunate interruption,’ Lock said. ‘Are you able to help us with this code? More to the point, are you willing?’

Kiran swallowed hard. ‘I do not wish to sound mercenary, Major Lock, but you said you would pay me for the work. It embarrasses me to ask, but I need to build up my savings. Of course, Trinity College will house and feed me, but there are other expenses — clothes, books, and so on.’

‘I quite understand,’ Lock said. ‘I’ll give you £10 for examining the code and another £10 if you can crack it. Do you accept?’

‘I accept.’

‘Good. Then I’ll bring the notebooks round to your lodgings first thing in the morning. And here’s my card. How quickly can you get to work?’

‘I will start work tomorrow morning, before Mr Smiggins and I go to the racecourse. We are in Newmarket for a few more days, so I’ll use all the spare time I have. Then we travel to Chester. The long train journey will give me valuable thinking time. I will write to you from Chester to let you know how far I’ve got.’

‘I’m relying on you, Mr Nambudiri. I need that code broken.’

‘Major, at the risk of sounding pedantic, I must tell you it’s not a code.’

Lock frowned. ‘What the deuce do you mean, not a code? It’s not in any language I’ve ever seen before. It must be a code!’

‘Let me explain, sir. In a code, a word or phrase is replaced with another word or phrase or symbol. A code requires a codebook which sets out these substitutions. That would be tricky for us, very tricky indeed. Indeed, I could be of little help to you. You would have to lay your hands on the codebook. But I’m confident there is no such item. No, what we have, it’s clear to me after my brief examination of the notebook earlier, is a cipher.’

‘Code. Cipher. What’s the difference?’

‘In a code, the substitution is at the level of a word or phrase. But in a cipher, the replacement occurs at the most fundamental level. Each letter of the original text is replaced with another letter, using a key and an algorithm.’

‘Algo what?’

‘Let’s just say there’s a fixed method behind a cipher. And that’s much better for us. There’s no codebook we have to find. The cipher is amenable to mathematical analysis. Though guesswork and intuition play a role too, as with all mathematical problem solving.’

‘I’ll have to take your word for that,’ Lock said with the air of a man who had given up trying to understand.

‘Did your brother have an interest in cryptography?’ Kiran said.

‘If you mean this business of ciphers, then no, not that I’m aware of.’

‘Again, that’s good for us. I’m hoping the cipher he used was not too obscure or idiosyncratic. Something to deter the amateur rather than the mathematician.’

They reached Kiran’s lodgings, a two-storey brick house on the Woodditton Road.

‘Here’s the first payment,’ Lock said, handing Kiran a ten-pound note. ’The notebooks will be with you in the morning.’

They shook hands and said goodnight.

Kiran looked up and saw that the lamp was still on in Mr Smiggins’ room. He had some explaining to do. And already, the memory of his odd experience in the dining room was fading in intensity and significance.

The notebooks arrived in the morning as promised, but Kiran didn’t start work on the problem until the evening. Mr Smiggins had convinced himself that the ‘friend from India’ was actually a rival bookmaker who was trying to poach his assistant. Kiran felt he had a duty of confidentiality towards Major Lock. And so his reluctance to share the nature or details of his assignment compounded Mr Smiggins’ illusion.

The delivery of a mysterious cardboard suitcase to Kiran only fuelled Mr Smiggins’ suspicions. Given how frosty relations between them had swiftly become, Kiran felt unable to retire to his room to work on the cipher. Instead, he accompanied Mr Smiggins on his morning walk around the town’s stables and training grounds. This was a routine intended to gather intelligence from any jockeys or stable lads that might be hanging around.

But it turned out to be a bad day for bookmakers in general, and Mr Smiggins in particular. The favourites won several races, meaning that losses on the bookmakers’ side were heavy. Kiran knew by now that this was part of the trade. There were good days and bad days. Bookmakers had to trust that the good days would outweigh the bad. And when they didn’t, they went out of business. Sometimes they even blew their brains out. Kiran had heard several stories from Mr Smiggins on this theme. But he knew his boss’ profits and losses very well by now. Mr Smiggins was a long way off the blowing-out-of brains stage.

Even so, the bookmaker was in a bad mood that evening, curt with everyone and downright rude with a few. Kiran was glad to leave the table early, after a meagre meal of bread, boiled potatoes, and cabbage. He thought wistfully of the feast Sergeant Draper prepared the previous evening.

Upstairs in his room, he opened the window as wide as it would go. Then he knelt in front of his portable shrine, rang the little bell, and lit the incense in its bowl. He washed the statue of Ganesha, the elephant-headed god of intellect and wisdom, and lay the daisies and poppies he had gathered from Newmarket Heath earlier in front of it.

He prayed to Ganesha and asked for his aid in solving the puzzle of the cipher. Kiran believed fervently that all his success in mathematics was divinely inspired and that mathematical formulas were nothing more or less than the thoughts of the gods and goddesses.

With these sacred duties performed, he took a notebook from the cardboard suitcase and a notebook and pencil of his own from the writing table. Sitting upright in the bed, his back resting against the headboard, his favourite position for thinking, he opened the notebook at a random page and read:

Thursday, 20th October 1881.

ISFJOGSCKRJLHIHHPGVGCQFWAMNDUHIWMVBGHYFINGTSVFTQNFCEWXNUOPVJBJITHVWVVHUSGLMOBGFVAOJTGSEZCPDTSUSVFFQFKQNKVG

The subject is a man in his late thirties, of plain, neat, and healthy appearance. He works as a plumber in the North London area and practices what he calls ‘spirit healing’ during his non-working time. His ordinary appearance is matched by the down-to-earth manner in which he talks about his supposed healing capabilities…

Kiran considered the string of letters beneath the date of the entry. Yes, it was definitely some kind of cipher. But there wasn’t much to work with. It would have been easier if all the text was encrypted, not just this part of it.

Kiran closed his eyes. Let’s assume that Dr Lock used something simple, something easy to encipher and decipher. And if he was an Englishman with a classical education, which Kiran assumed was likely, then a cipher from antiquity might be appealing. Specifically, the shift cipher used by Julius Caesar to encrypt messages for his military commanders.

In the form reported by the historian Suetonius, it involved a shift of three letters to the right, so that A in the plaintext becomes D in the ciphertext, B becomes E, C becomes F, and so on. Simple, but just complex enough to deter the person who knows nothing of ciphers.

Kiran spent the next several hours trying all twenty-five variations of both the leftward shift and the rightward shift.

It was a fruitless exercise. Dr Lock had not chosen the obvious cipher. Kiran was tired and had another busy day ahead of him. Before he went to sleep that night, he offered another prayer to Ganesha.

Two days later, Kiran was standing on the northbound platform of Newmarket railway station. He and Mr Smiggins were waiting for the train that would take them to Cambridge, where they change to a Birmingham train. At Birmingham, they would pick up the Chester train.

Kiran had spent what little spare time he had on the Lock cipher. Having tried and exhausted all the simple approaches, he was now carrying out a detailed frequency analysis. The idea behind this standard decryption technique was that, in all languages, some letters occur more frequently than others. In English, the commonest letter is e, followed by t and a. By counting the frequency of letters in the ciphertext, one could make some guesses about the plaintext.

But it wasn’t that simple. In the first place, Kiran had relatively little text to work with. And in the second place, modern encryption techniques used different cipher letters for the same plaintext letter. Which meant that the cryptanalyst had to look for other patterns as well, such as the pairing of letters. It was fiendishly complicated and very time consuming.

But for Kiran, it was tremendously enjoyable and, with the help of Ganesha, he felt certain he would crack it. The real question was how much patience Major Lock had. He had written to the Major outlining his progress to date and asking if they could meet in London. Kiran had an idea about how the process might be shortened by gaining some insight into Dr Lock’s mind.

As the Cambridge train arrived, Kiran and Mr Smiggins prepared to board it. But when he picked up his suitcase, Kiran became dizzy and disoriented. It was the same feeling he had experienced in the dining room of the White Hart, though less intense.

As he tried to steady himself, he glanced along the platform and saw a boy watching him with interest. Fair hair, angelic features — it was the face he had seen before he blacked out. Only this time, as far as Kiran could tell, it was flesh and blood.

The boy smiled at him. Yes, he was flesh and blood...