RED cipher machine challenge

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The RED cipher machine was created by japoneses about 1930. It was used by japonese embassies. RED is the codename given by American's cryptanalists. In fact it genuine name is 91-shiki ohbun-injiki (System 91 Printing Machine) or Angoki Taipu-A (Type-A Cipher Machine). The RED cipher was replaced by Purple machine.

The RED system is not very secure. The most serious flaw is the separate encryption of the vowels. The RED system was broken successfully by several independently working groups: The British, The American Navy (OP-20-G), The American Army (SIS), The German, (perhaps the Soviet?).

Problems (notes)

1st Problem (very easy)

Luigi Tomelli 30/01/19

Rafael Pascual 08/07/20

García Larragan 14/07/21

G. Lasry 29/05/25

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2nd Problem (easy)

Luigi Tomelli 30/01/19

Rafael Pascual 12/07/20

García Larragan 14/07/21

G. Lasry 29/05/25

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3rd Problem (medium)

Luigi Tomelli 30/01/19

Rafael Pascual 20/07/20

G. Lasry 30/05/25

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4th Problem (medium)

Luigi Tomelli 30/01/19

Rafael Pascual 14/07/20

G. Lasry 30/05/25

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5th Problem (easy)

Rafael Pascual 27/07/20

G. Lasry 30/05/25

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6th Problem (difficult)

Rafael Pascual 29/07/20

G. Lasry 31/05/25

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7th Problem (difficult)

Rafael Pascual 24/08/20

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8th Problem (medium)

Rafael Pascual 02/01/22

G. Lasry 31/05/25

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9th Problem (medium)

Rafael Pascual 03/09/20

G. Lasry 31/05/25

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