Hebern: 1st Problem (HINT)

Munitions Buildings, Washington D.C.

Signal Intelligence Service

February 9th, 1931

My Dear students,

Now, you know much about cipher machines. You
are ready to investigate a complex one: The
Hebern’s cipher machine.

This machine consisted essentially of four
components, as follows: a keyboard similar to a
typewriter keyboard, a lampboard which is a
bank of twenty-six illuminated windows on each a
letter of the alphabet was inscribed, a cipher-
decipher switch, and, most important from the
cryptographic viewpoint, a set of five rotors
operating in cascade which provided for the
enciphering deciphering of the device.

In the cipher mode, the enciphering current
flowed from left to right and passes through the
keyboard, the five rotors and the lampboard. In
the decipher mode, the deciphering current
flowed in reverse direction from the lampboard
to the keyboard. Remark: One can cipher in the
deciphering mode, then the mode (ciphering or
deciphering) is part of the key. The rotors are
inserted into the machine in a prescribed daily
order known to both correspondents. The rotors
could even be inserted backwards, then the
machine to function as 10 distinct rotors.

On the extreme left was the left ratchet wheel
followed by the five rotors which we denote I, II,
III, IV and V, followed by the right ratchet
wheel. As each letter of the plaintext was
depressed on the keyboard, rotor V (the fast
rotor) stepped one position forward (before
encipherment). The right ratchet wheel also
advanced one step with each letter enciphered.
When the right ratchet wheel reached the letter
N on the machine’s benchmark, the ratchet
arrangement then caused both the left ratchet
wheel and rotor I (the medium rotor) to advance
one step. Thus, after the first time, N is reached
on the right ratchet wheel, the left ratchet
wheel and rotor I are stepped once for each
revolution of rotor V. The left ratchet wheel
drives rotor III (the slow rotor) whenever it
reaches N on the benchmark in a similar manner.
The rotors II and IV are stators.

A sample rotor movement starting at the
External key MEANING is show below:

Left Ratchet Rotors I II III IV V R. Ratchet

M E A N I N G

M E A N I O H

M E A N I P I

M E A N I Q J

M E A N I R K

M E A N I S L

M E A N I T M

M E A N I U N

N F A N I V O

N F A O I W P

N F A O I X Q

N F A O I Y R

N F A O I Z S

The wiring of the rotors, keyboard and lampboard:

Keyboard: XAKHSZJLYWGPMIOURDBFTNVCQE

Rotor 1: GADBOCTKNUZXIWHFQYJVPMELSR

Rotor 2: IZNCTKUDPJEVOWLFHXSMGQAYBR

Rotor 3: PJXFWLTAUGYBMHROVNCKSEQIZD

Rotor 4: FLVARGWCMQBXNYIOTJUPSKEDHZ

Rotor 5: FQTGXANWCJOIVZPHYBDRKUSLEM

Lampboard: TYOEUMXDFJQVKWBNSHCILRZAGP

Your first assignment is very simple: you must
design a pencil and paper device which emulates
the function of the Hebern cipher machine. With
this device you must decipher the following
message. The key is given.

W. F. Friedman

Message:

IRAKW XFIHL ULFIB RZLTD DYLTF JHQPI YROWY

QLXIQ GYSIO YLSYM ERMWL MNZXS QVFJE SQHRG

LFJGO TFBGD JGGLQ YYOFW MPUVU QQNKY GECZT

RPOTZ WHCDF RNHMR UXFPF RFENG PCGOJ CHOAW

RXVYS FQVXO LFBAU RQQMK CGFFW TRFUC YICTM

WWODP JMLQN QXZZO LUUHL AZHAG VXCKW HOTRB

IJICV BUMCP WDIII VNKSV RWJHQ DCOFS JFKLT
NPJXD HKAAX EAMOG LAAWX MGEHW SPRGT CLJYZ
XGGDF GXXXX

Rotors order: 4:1:5:3:2

External Key: MACHINE (Left Ratchet, Rotor I, II,
III, IV, V, Right Ratchet). All rotors are inserted
in Forward direction (not Backward)
The machine is set in cipher mode.