The Checking Machine

Enigma Home Page

Introduction

A Checking Machine is a simplified Enigma: There is no steckers and rotors (here called drums) are forward or backward by hand. On the other hand, as on a normal Enigma, if you press on a key of the keyboard a lamp lights up.

A checking machine was used in conjunction with a Bombe to test a stop.

My simulators

I have written several cheching machine simulators. All were written in Python.

My text simulators

A simple simulator for M3 Bombe

This simulator is very simple to use but it only allows to simulate an Enigma M3.

A simulator for M3/M4 Bombe

This simulator is provided in the package that houses the graphical simulator. In fact it uses the same library. It is more complex to use but more powerful.

My graphical simulator

The simulator can emulate an Enigma M3 or M4.

The simulator is composed of several parts:

  • The drums (the rotors of an Enigma) [cf. below for details].
  • The lamps (the encrypted letter appears lit).
  • The keys of the keyboard (we click on one of the keys to encrypt a letter).
  • The bottom area lists the available drums.

The drums are drawn in the upper part. The empty slots that should house them are represented by four pink circles.

  • X The leftmost slot. Normally, we put the drum "straight" in this slot to work in Enigma M3 emulation mode.
  • S (Slow) is the second slot from the left. We put in this place the drum corresponding to the left rotor of an Enigma M3.
  • I (Intermediate), it's the third slot from the left. We put in this place the drum corresponding to the middle rotor of an Enigma M3.
  • F (Fast) is the fourth slot from the left, so it's the right one. We put in this place the drum corresponds to the right rotor of an Enigma M3.

To emulate an M4, you have to configure a reflector (Uncle Walter or UKW) using the menus. You can choose Thin-B or Thin-C. Then, you have to choose the beta or gamma drum in the slot X (the leftmost one).

To emulate an Enigma M3, you have to put the drum "straight" in the slot X (the leftmost one). Drum straight wiring is simple: A->A, B->B, C->C, ..., Z->Z. Its presence (and its grundstellung) does not change the cipher in any way. The drum straight is completely transparent. By default, the reflector used is B. Via the menus, you can change it (A, B, C).

Example of using my Checking Machine simulator

Key

Walzenlage:
  • UKW:B
  • X: staight
  • Slow: IV
  • Intermediate: I
  • Fast: III 
Grund., clear -> encrypted letter

AONO        H -> B
AONK        H -> A
AONR        A -> J
AOOG        H -> Z
AOOH        Z -> S

References

  • The US 6812 Bombe Report describes in details a Checking Machine and its using
    (The Report)