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

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

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