HCM 5 rotors, Challenges

Introduction

In the page concerning the cryptanalysis of the 5-rotor HCM machine, I present different methods of attacking this machine.

If we want to convince ourselves that we have mastered the methods presented, solving concrete problems is the way to follow. In my web page devoted to cryptographic challenges of the period between the two wars and which includes the Second World War, one of these pages is devoted to associated problems about the Hebern 5 rotor machine from the time of the first challenge won by Friedman in 1924.

The problems

The 1st Problem

This problem is not difficult.... Except that it is necessary to create a simulator of the Hebern machine (paper or computer). To achieve this goal, one must have read carefully the text accompanying the problem.

Note: You can also use the tools that I provide, like my simulator.

The 2nd problem

The rotors order and the beginning of the message are known. You can try all message keys. In an other hand, it is possible to find the fast rotor by isomorphs method. Then no computer is needed.

The 3rd problem

You need to calculate IC for each possible rotor. Manual calculations are still possible but using computer is easier.

The 4th problem

The beginning of the message is known but the are many rotors orders to try. A computer is (almost) needed.

The 5th problem

Calculate IC seems the right solution ... but perhaps you will find a short cut?

The 6th problem

The starting positions of the rotors are known. It is possible to recover the wiring of the unknown rotor without computer.

The 7th problem

This problem is the same that W.F. Friedman solved in 1924. Are you as gifted as him?

The 8th problem

This problem is almost the same that W.F. Friedman solved in 1924. There is a big difference: the messages were ciphered in REVERSe mode!