RHV Part 1 - Kenngruppen

By Michael Hörenberg

Suppose we would like to send a WW2 naval message encoded with the "Reservehandverfahren" (R.H.V.) procedure. First we need to determine the "Kenngruppen" (message indicator groups).  With the "Kenngruppen" the receiver of our message can reproduce the message key and the procedure used to encode the message. The Kenngruppen are the first and the last two groups of our radio message.

We need two groups. The so called "Schlüsselkenngruppe" and the "Verfahrenkenngruppe". (key indicator group and procedure indicator group)

Bild "Zuteilungsliste"
The "Kenngruppenbuch" K-Book helps. First we need two 3 letter groups within the range of RHV. The "Zuteilungsliste für Kenngruppen" (indicator group selection chart / Z-Liste) tells us, that we can use indicator groups from the K-Book within a range of 201-250 ("RHV-Schlüsselkenngruppe"). For the "RHV-Verfahrenkenngruppe" we can use groups within the range of 291-733.

Bild "K-Book Spaltenliste"
K-Book Spaltenliste
Schlüsselkenngruppe: We choose JKG from column 217 and row 6 from the Kenngruppenbuch part 1 Spaltenliste (column list).

Bild "K-Book Spaltenliste"
K-Book Spaltenliste
Verfahrenkenngruppe: We choose JMK from column 320 and row 13 from the Kenngruppenbuch part 1 Spaltenliste (column list).

The rows we choosed are part of the message key! Keep it in your mind...

Now we must process the Kenngruppen in the same way we would do it with Enigma Kenngruppen. This is necessary to obtain two encrypted 4 letter indicator groups.

(B) J  K  G    Schlüsselkenngruppe
J  M  K (X)   Verfahrenkenngruppe

(B) and (X) --> user-defined by the radio operator.

Bild "Tauschtafel"
Tauschtafel A
Suppose the "Doppelbuchstabentauschtafel für Kenngruppen" (bigram substitution table(s) for indicator groups) of the day is "Quelle" Tafel A. We got this information from the Tauschtafelplan für Kenngruppen (table selection chart). We take the letters in pairs vertically and look them up in the  Tafel A.


The four "new" pairs are then arranged horizontally:


We created our message indicator groups!

--> Part 2