hannover, 18th january, 1917.

“herr scherbius, what are you working on this late?”

“ah, hermann, young lad. how nice to see you! what are you doing here at this late hour?“

“i am sorry to intrude, but i forgot my copy of ‘his last bow’ and i am curious as how mr. holmes will figure it out, i just did not want to wait until tomorrow to find out.”

“ah, hermann, always with your head in a book. have you read the latest of h.g. wells?“

“are you referring to ‘mr. britling sees it through’?”

“yes, that would be the one.“

“not yet. i am not sure i will read it though.”

“why not?“

“i’ve heard that it advocates for a different world with more open international collaborations, and i am not ready for ideas like that. it feels like the opposite of the vision of a great and strong germany. the germany my father always talked about and envisioned.”

“yes. terrible loss, your father. he was a brilliant man. in fact. it was after one conversation i had with him, many years ago, that the first idea of this invention came to me.“

“what is it?”

“before i tell you. it is most important that you keep it a secret. from every one, even your lovely wife back home.“

“you have my word.”

“good boy. i know i can trust you. but before i talk about the machine. you know of substitution crypto’s, yes?“

“yes. my father taught me when i was little. we used to send secret messages to each other using different substitution keys for each day of the week.”

“then this will be no match to grasp. it’s just a prototype, and i have figured out the basics of the mechanics behind it, but it needs a lot of refining before the final product. it is like a substitution crypto typewriter, but currently with four keys. i’d like to get it down to a single key to make it more appealing to work with.“

“how does it work?”

“see these rows with wheels? there is where the keys are entered. and once you have aligned them with your desired keys, you just type what you want to say. try it!“

“anyting?”

“yes, what ever you like…“

“i write ‘sherlock holmes’”

“and what comes out on the paper?“

“zb24kofz bo5m2k”

“now, push that switch to reverse the machine, and write what you just got out of the machine.“

“sherlock holmes. amazing!”

“indeed it is, isn’t it. now change the settings on the keys. just at random now, ordinarily, for it to work properly you need to make sure all letters and numbers appear only once in each key, but for demonstrational purposes, that is not necessary. what does it say now when you decode the message?“

“do2g9r8r pq6gwp”

“yet it is still the same machine, same mechanics behind it, but it scrambles the letters completely different, and as you can see, sherlock holmes has s, h, e, l and o twice. and in an ordinary substitution crypto they would be the same. now you have replaced h with the letter o on one place and the letter p on the other. and on top of that, both p and r are used multiple times in such a short message as this.“

“indeed increadable.”

“now, decode this text. and use these four keys.“

key 1: y3j2drstzvme9poc6x17wlnbquaif854hg0k

key 2: mzqeab7n1t4ck86l9os0wy23dhp5vigjrfxu

key 3: qlvnrbgy96w3dthkoxi5m4p17ces20uj8zfa

key 4: py0hs2kwmb4qx76irzldn1e8jftauvo95cg3

the message: 1myzy0i eq9mye 02 y2zm k21 lynxp7s zyyqk3m9 vob6 nbmy.