RHV Part 3 - Message encoding procedure
By Michael Hörenberg
Example: The following radio message is given to the radio room:
Aufgabe Durchgeführt. Einlaufen Emden zur Kohlenergänzung 17.4. morgens.
(To the Commander of Security of the North Sea [and to] the Leader of Minesweepers West: Task carried out. Arriving at Emden on the morning of 17th April for replenishment with coal. 4th Minesweeper Flotilla.)
The message is to be made ready for transmission according to the radio procedure in force (M.Dv.Nr. 32/1):
Prepared plain text:
virte minflo an an b s nnn und f d mmm west x aufgabe durchgefuhrt x einlaufen emden zur kohlenerganzung eins siben x vier x morgens
RHV KastenwürfelWith the information from Part 2 we can create the so called "Kastenwürfel" (transposition box). Now we use the "Zahlenreihe" (number sequence). The letters of the plaintext must be divisible through 4 without remainder, to obtain an even number of groups. For our example: We got 106 letters, so we have to fill 2 additional letters to the box. 108:4=27. We use the two consonants "p" and "c".
Notice: We fill the box horizontally. Read-Out is vertically.
RHV cipher formStep 1: The read-out order is given by the numbers of the number sequence on the top of the box. Four letters are forming the so called "Buchgruppen" (Book-Groups). We write them on the right hand side on the Schlüsselzettel (cipher form). Example: NMRU LSGF ... This is the transpositon stage of the RHV system.
Step 2: Now we perform the bigram substitution. For this step we need the RHV-Schlüsselheft (RHV Code-Book). This document contains a set of bigram substitution tables. In our case we use the table sequence 11 6 9 16 (see also Part 2 of the procedure). We form pairs of two letters vertically and look them up in the substitution tables. Notice: Every column has its unique table. Example: NL --> FM (table 11) or MS --> PN (table 6) and so on... The last two pairs of the message are formed horizontally (table 11 and 9). We write the new pairs vertically on the left hand side of the cipher form: The so called "Funkgruppen" (radio groups --> ready to transmit). We created our RHV ciphertext!
The RHV encoded message with Kenngruppen (indicator groups) looks like:|
MCBP JQTB FPDZ MNRE LPDU OZHI BUSB ROLH KQFQ RHPA HTCL KWCL YVDJ YDBT KGTA DHCQ EMDE CIAQ QCKH VHGP WDIS DIZC RDSQ HCLA YNPD INKL ZWYM KFPJ HLZG MCBP JQTB
RHV SchlüsselheftOriginal "Schlüsselheft Nr.16 zum R.H.V Allg."
(Explicit graphical representation removed)
RHV TauschtafelOriginal "Tauschtafel 11" from "Schlüsselheft Nr.16 zum R.H.V Allg."
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