Reservehandverfahren (R.H.V.) M.Dv.Nr. 929/1

By Michael Hörenberg

Bild "Reservehandverfahren"
M.Dv.Nr. 929/1
Reservehandverfahren (RHV) (English: Manual Backup Procedure) was a German Naval World War II hand-cipher system used as a backup method when no working naval Enigma machine was available. The cipher had two stages: a transposition followed by bigram substitution. In the transposition stage, the cipher clerk would write out the plaintext into a "cage" or "box" — a shape on a piece of paper. Pairs of letters were then substituted using a set of bigram tables. A RHV encoded radio message looks exactly like an Enigma radio message.

M.Dv.Nr. 929/1 = Marine Dienstvorschrift Nummer 929/1

(Explicit graphical representation removed)

Several documents were necessary to encrypt/decrypt a message with RHV:

  • Der Schlüssel M - Verfahren M Allgemein (ENIGMA Procedures M.Dv.Nr. 32/1)
  • Kenngruppenbuch (K-Book)
  • Zuteilungsliste für Kenngruppen (indicator group selection chart)
  • Tauschtafelplan für Kenngruppen (substitution table selection chart for indicator groups)
  • Tauschtafeln (a set of bigram substitution tables for "Kenngruppen" e.g. "Quelle")
  • RHV Tauschtafelweiser (RHV table sequence selection chart)
  • RHV Zahlenreihentafel (RHV number sequence selection chart)
  • RHV Schlüsselheft (RHV digraphic / bigram substitution tables)

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