Intercept #1

First Transmission

The intercept

Eastern Front, summer 1943. A radio operator has just copied down an intercepted transmission. No message key to untangle yet: set the machine to match the sheet, turn the rotors to the message key below, and start typing.

Transcription

Netz: Luftwaffe – Fernaufklärung Ost
Datum: 14. Juli 1943
Walzenlage: II – I – III
Ringstellung: 24 16 12
Umkehrwalze: B
Steckerverbindungen: QW ER TY

Message key: JLC

Ciphertext

CEUNY VDAOI VNXBV YETEI GFIUU AHFKX OIVWZ SCGQZ

Notes

This warm-up hands you the message key directly. Real traffic sent it encrypted at the head of the message. Challenge 3 covers that procedure.
The plugboard is also simplified: three pairs here, where real 1943 Luftwaffe sheets used ten.
On the Enigma touch, work through the setup modes left to right: Modell, Rotor, Ring. Then leave setup mode (tap the lit button again) and turn the rotors to the message key with the sprockets.
Spaces are left out, and the message follows the manual’s message-prep rules (§2.3). The ciphertext is written in groups of five for readability. The groups aren’t part of what you type.

Hint

Click for a hint

Enigma doesn’t distinguish between encryption and decryption. Type the ciphertext in with the sheet’s settings and the message key on the rotors, and the plaintext lights up in the lamp field.

Three rotors under Walzenlage and ring settings written as numbers mean Modell I, the Army and Air Force machine.

The Enigma I shows rotor positions as numbers, but message keys are written as letters. Convert the letters (A = 01 … Z = 26), or read the conversion off the plugboard sockets, which are labelled with both. JLC is 10 12 03.

Solution

Click to reveal the solution

Plaintext: AUFKLARUNGMELDETPANZEROSTWARTSSMOLENSKXX. It reads “Aufklärung meldet Panzer ostwärts Smolensk” (“Reconnaissance reports armor east of Smolensk”). Two of the manual’s message-prep rules show up here. ä is written as plain a, so “Aufklärung” becomes AUFKLARUNG. The closing XX is padding to make the length a multiple of five.

Full trace

With the sheet dialed in exactly as given, the rotors at JLC, and AUFKLARUNGMELDETPANZEROSTWARTSSMOLENSKXX typed in, the lamp field lights letter by letter:

A->C   U->E   F->U   K->N   L->Y
A->V   R->D   U->A   N->O   G->I
M->V   E->N   L->X   D->B   E->V
T->Y   P->E   A->T   N->E   Z->I
E->G   R->F   O->I   S->U   T->U
W->A   A->H   R->F   T->K   S->X
S->O   M->I   O->V   L->W   E->Z
N->S   S->C   K->G   X->Q   X->Z

This was a 3-rotor Luftwaffe setup on Modell I. The Army (Heer) used the same machine, on different radio nets with different keys.

easywarm-up

Solvable on: Enigma Touch, Physical Enigma replica, cryptii.com Universal Enigma — set the model to match the key sheet.

Reading the key sheets

The sheets use the German column names of real key sheets. Walzenlage is the rotor order, Ringstellung the ring settings, Umkehrwalze the reflector, andSteckerverbindungen the plugboard connections. Netz andDatum are the radio net and the date.

Rotors and ring settings are listed left to right, in the same order you enter them in the Enigma touch's Rotor and Ring setup modes. Plugboard pairs have no order: swapping the two ends of a cable changes nothing.

The Enigma I labels its ring settings and rotor positions with numbers (A = 01 … Z = 26). Message keys are still written as letters, so convert them before turning the rotors. The plugboard sockets are labelled with both.

The Kriegsmarine's four-rotor M4 has a fourth, thin "Greek rotor", β (Beta) or γ (Gamma). It is listed first under Walzenlage and has its own ring setting and rotor position. It never moves while you type. The reflector letter (B or C) is written the same way on every machine.

Enigma doesn't distinguish between encryption and decryption. Type the ciphertext in with the rotors at the message key and the plaintext lights up in the lamp field. Spaces aren't part of the Enigma's alphabet, so add them back once the message is decoded.