Equestria: World War II (1939-1941)

20TH MAY 1940

-------------------------------------------------------BLETCHLEY PARK, MILTON KEYNES------------------------------------------------------
It was now 11:00am here in Britain, which meant it was around 9:30am back in Equestria. Twilight and Cadance were stepping up to the large mansion that was Bletchley Park. The mansion, which had formerly been owned by a builder, had been bought two years earlier by the S.I.S. for use as the Government Code and Cypher School (GC&CS). This was a part of the British intelligence agency that broke the encryptions used by the German military.

Recently, the head of the operation being run here had actually asked if Equestria and the Crystal Empire had any skilled cryptologists to send for this programme. Apparently, the Germans were using some sort of new encryption that seemed impossible to break, and they had a lot of great things about pony cryptologists, and they had asked for their expertise. Celestia had heard that Twilight had recently been taking a cryptology course at a now-famous university in Equestria, so she had sent Twilight here, and some more pony cryptologists would follow shortly.

Cadance had also come along to drop Twilight off, as she was anyway conducting a state visit to Britain, so she had decided to accompany Twilight on the beginning of her stay at Bletchley Park. Twilight suspected she would probably be here for some months, to help break whatever this mysterious encryption was. As the car carrying the two stopped outside the mansion, Cadance asked, "Twilight, are you sure about this? You probably won't be coming back home for months, maybe even years, so are you ready?"

"I know, Cadance, but I'm so ready for this! This is an opportunity like no other, and I'm definitely taking it! If I refuse now, I won't get it again!" said Twilight.

"Look, I know you feel confident after staying in that military base with your brother for a few months. But still, its been a while since you were outside Equestria. But are you truly sure?" asked Cadance.

"Yes, Cadance, I'm ready for this. I've been preparing for this ever since Celestia assigned me this task, and if I fail at this, the fate of the whole world could be at stake. I'm ready." said Twilight, as she began getting out of the car, taking her things. "I'll see you in a few months." said Twilight, smiling as she waved Cadance goodbye, and began heading towards the mansion, with her things along. She headed towards the main door, where a man was waiting. He was quite a young fellow, in his late twenties, with brown hair, and a friendly face.

"Miss Twilight Sparkle, I presume?" asked the man.

"Yes, I'm Twilight Sparkle, unless there is another purple unicorn that looks just like me and has the same name, of which the chance is less than one trillion! So, yes, I am Twilight Sparkle! And you are..." said Twilight, not knowing who this man was.

"Alan Turing. I'm the lead cryptologist working here at Bletchley Park. I'm quite skilled, but we are having a lot of trouble trying to decrypt what the Germans have been using lately. They've been using some of the craziest encryption I've ever seen in my life. If you want, you can take a look at it, but me and my team have basically have been banging our heads over it. It's that complicated."

"I'm more than happy to take a look! I wonder how good this encryption is if even you can't break into it, considering the things I've heard you've done." said Twilight, as she and Turing headed towards the area where the cryptologists were currently working.

As they headed towards that part of the large mansion, Twilight asked Turing, "So, how has it been going so far in breaking the Germans' encryptions, and figuring out whatever they are up to?"

"Well, the Polish have somehow managed to make a machine called the Bomba. It was built in 1938 by a reknowned Polish cryptologist, his name was Marian, I believe, and it has successfully been used to break the codes of some of the Enigma machines used by the Germans. Those are the cipher devices they use to communicate with their higher-ups on the field, and they were considered so secure that the Germans used them to encrypt the most top-secret messages. However, it is quite a rudimentary method."

"Rudimentary? How so? Have any messages already been intercepted?"

"Well, the Bomba is based on a procedure that uses indicators. In the Enigmas, each message has its own key. Usually, the transmitting operator informs the receiving operator of this message key by transmitting some plaintext or ciphertext before the enciphered message. This is the indicator, as it indicates to the receiving operator how to set his machine to decipher the message."

"Isn't that an insecure method, as the Germans could change that system at any moment?"

"Yes, and indeed, they have. They changed the indicators earlier this month, so all of our hard work has basically gone down the drain, and now, we have to start all over again. Plus, our intelligence has found that the Germans seem to have rolled out a new model of the Enigma, which so far we have not been able to decrypt at all. However, we are working on decrypting some of the relatively older models, which the Germans are still using, thankfully, otherwise, we would never know their next moves."

"Oh, I see! So how are you able to decrypt those, if you have been able to, without the Bomba method?"

"Well, thankfully, I have developed a new method for that. You're about to see the unveil of the method that I have developed, and here's my team now!" said Turing, as they reached the part of Bletchley Park where the main team of cryptologists was working, and when Turing entered the room, they all stopped what they were doing and looked at him and Twilight.

"Gentlemen, this is Twilight Sparkle, an exchange cryptologist who has come all the way from Equestria to join us. She's quite skilled, and she's going to be working with us to help decrypt the new Enigmas. But today, I also have something else to show you. We have all been having a hard time trying to decrypt the Enigmas, ever since the Germans changed their indicators, so the Bomba is pretty much useless right now. However, I've been developing a new method to help get over the Bomba's limitations." said Turing, who was standing in front of a large whiteboard.

"So what is this new method? Will it actually work?" asked one of the other cryptologists, a little skeptically.

"Well, this new method is a bit more of a general approach. We're going to use crib-based decryption to complete our mission here. Crib basically means any known or suspected plaintext in an enciphered message."

"Didn't the Polish already try that in the early days of the war?" asked Twilight.

"Yes, but they used only six leads on the plugboard, the Forty Weepy Weepy method. The cribs are going to be essential to the method I've made to solve the Enigma keys. Here's the thing. No letter can be enciphered as itself, so I've combined every plaintext fragment, a corresponding ciphertext fragment can often be tested by trying every possible alignment of the crib against the ciphertext. That is what I call crib-dragging, and it's quite painful, so I dug up some more information." said Turing, as he began writing on the whiteboard.

"I had some captured Enigma operators of the German Army interrogated, and they revealed that they had been instructed to encipher numbers by spelling them out rather than using the top row of the keyboard. I reviewed the decrypted messages and determined that the word eins, or 'one', appeared in 90% of the messages. I automated the crib process, by creating the Eins Catalogue. This assumes that eins is encoded at all positions in the plaintext. This catalogue includes every possible rotor position for EINS with that day's wheel order and plugboard connections. It is going to help reduce our workload, and make it easier. I also have plans to create a new device, an improvement on the Bomba. Who's going to help me?" said Turing, as his colleagues clapped at his method, and began cheering for him.

"Alright, you're all helping me build this device, especially you, Miss Twilight! Come on, let's get to work!" said Turing, as he, Twilight, and his cryptologists began getting to work right there on the spot. They began the planning and creation of the new cipher breaking device, one that would help change the course of the war entirely. If it worked, it would probably help shorten the war, by a long time. If it didn't, Discord would dominate the whole world.