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Challenge "Enigma Combinatorics"

Challenge "Enigma Combinatorics"  

  By: admin on Nov. 12, 2010, 3:29 p.m.

The Enigma is an electro-mechanical rotor machine used for encryption and decryption. One main part of the Enigma is changeable rotors. This challenge deals with the calculation of the key space.
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 Last edited by: admin on Oct. 31, 2021, 2:54 a.m., edited 1 time in total.

Re: Challenge  

  By: DarkFibre on June 17, 2011, 12:29 a.m.

There is no such machine as an "Enigma-1." I assume the author meant the "Enigma I" (model i) machine, and not "Enigma model A" but that changes many of the answers.

What does "padded without a delimiter" mean? Does the author mean it is padded with spaces? If my answers were 1, 2, 3 how would I enter them? "123" or "1 2 3" or something else?

Re: Challenge  

  By: Lotus on June 18, 2011, 1:24 a.m.

There is no such machine as an "Enigma-1." I assume the author meant the "Enigma I" (model i) machine, and not "Enigma model A" but that changes many of the answers.

What does "padded without a delimiter" mean? Does the author mean it is padded with spaces? If my answers were 1, 2, 3 how would I enter them? "123" or "1 2 3" or something else?

Enigma I is correct. The basics used for the calculation are explained in the challenge text. 3 out of 5 normal rotors and 1 out of 2 reflectors.
Please enter the answer like this 123.

One of your answers was nearly correct, but you forgot the last question.

Greeting,
Dennis

Re: Challenge  

  By: fretty on June 27, 2011, 11:02 a.m.

I am stressed with this challenge! I have absolutely no idea which of my answers is incorrect, they seem right to me.

Can anyone tell me whether for questions 1 and 2 the word "positioning" means just the order of choosing the 3 rotors or this along with corresponding rotor settings too (A-Z)?

Is there anyone I can PM to check my answers?

Re: Challenge  

  By: Lotus on June 28, 2011, 1:06 p.m.

Can anyone tell me whether for questions 1 and 2 the word "positioning" means just the order of choosing the 3 rotors or this along with corresponding rotor settings too (A-Z)?

Just the order.

Is there anyone I can PM to check my answers?

Yes, if you want i can check your answers.

Greetings,
Dennis

Re: Challenge  

  By: Lotus on June 29, 2011, 1:56 p.m.

Yes, if you want i can check your answers.

Done.

Greetings
Dennis

Re: Challenge  

  By: fretty on June 29, 2011, 2:04 p.m.

Many thanks for checking my answers.

The problem I had was with Q3, it doesnt say that we are choosing a reflector and an "ordered" triple of rotors, just 3 rotors (in any order). Maybe this needs changing or am I reading it wrong?

Re: Challenge  

  By: DarkFibre on June 30, 2011, 1:17 a.m.

Thank you for the response!

Re: Challenge  

  By: stef_the_chef on July 8, 2011, 5:58 p.m.

Ich versteh die 4. Frage nicht ganz.
Die Umkehrwalze ist doch fest oder nicht??

Ansonsten bin ich mir bei dem Antworten ziemlich sicher, falls ich alle richtig verstanden habe.

edit: ok, habs mir eigentlich selbst beantwortet

Re: Challenge  

  By: fretty on July 8, 2011, 8:49 p.m.

Yes, the reflector is chosen already and the question wants to know how many start positions there are for this piece of the machine.

Re: Challenge  

  By: Veselovský on Oct. 1, 2011, 10:45 p.m.

The questions are stated too ambiguously.

Question 1: What is meant by positioning of rotors. The position in slots, starting position and rings setting or without ring settings?

Question 2: Same as question 1.

Question 3: This one looks unambiguously.

Question 4: quote: "How many possible start positions exist for the chosen
reflector?"
The question ask for start positions of already chosen reflector itself, not for starting positions of the rest of rotors as is written in the last fretty's post. So the correct answer to this question would be 26 (which, I guess, will not be the same as the required answer as it would be too easy)

Question 5: Again similar ambiguity as in question 4.
quote: "…how many possibilities are there for the start
position of the third rotor"
there are always 26 starting position for any rotor (if we do not count ring settings)
So the answer should be again 26.

Question 6: This one looks unambiguously.

Question 7: quote: "…Enigma machine has four normal rotor slots
and you already chose the order…"
You can not choose the order without firstly choosing 4 rotors. (it is like I said you: You have four unknown numbers, choose their order! …you can not, because it has no sense until you know what the values of these four numbers are. So if I said you: You have four numbers 2,3,5,7 choose their order! Then you can choose for example 3,5,2,7)
So I understand the question as I already chose 4 rotors out of 5 and chose their order in the slots. Then the question is too easy, so I think it was again meant differently than it is stated in the question.

Question 8: This one looks unambiguously.

I hope I was not ambiguous too and would like someone (who perhaps have already solved it) to paraphrase these 8 question (maybe only 5, 3 were fine to me) in an unambiguous way and explicitly stating where rings settings are considered and where are not.
Thanks

Re: Challenge  

  By: Veselovský on Oct. 1, 2011, 11:04 p.m.

The fact that the questions are ambiguously stated is confirmed by this:
quote: "19 users already solved this challenge, 27 users are working on it."

…I have to say… ONLY 19 and EVEN 27
There is only one another challenge in Level I where first number is smaller than the second one (19<27)
The other one is Zodiac cipher (which I personally think is more difficult then this challenge)

There would be much more successful solvers if questions are stated more clearly.
I do not understand why anybody of these 27 unsuccessful users haven't write a single post in the forum and haven't ask for clarification of the questions.

Re: Challenge  

  By: fretty on Oct. 2, 2011, 10:50 a.m.

Some of the questions are slightly ambiguous but common sense prevails. You should read the slides before the questions…you will then see for example that the phrase "starting position" is nothing to do with "ring settings".

Q1 - You choose 3 rotors, how many different ways are there to place them in the machine?

Q2 - You have 5 rotors, how many different ways are there to place three of them in the machine?

Q3 - This is the evil one. How many different ways are there to put a reflector and 3 rotors into the machine? This question needs changing at least since it just mentions choosing rotors and reflector, not actually putting them into the machine (in the first problem order doesn't matter whereas in th second it does).

Q4 - This one is not ambiguous…it is just a trick question. Does the reflector even move?

Q5 - You have put 3 rotors in the machine and have set the starting position of 2 of them. How many ways are there to set the starting position of the 3rd? As I said earlier, if you had read the description before the questions you would know exactly what "starting position" meant and would find no ambiguity here.

Q6 - Unambiguous.

Q7 - Also unambiguous, it tells you exactly what you need to know. You have put 4 rotors into a machine, how many different starting positions are there? Again this does not mean ring settings.

Q8 - Unambiguous.

Re: Challenge  

  By: Veselovský on Oct. 2, 2011, 3:01 p.m.

Thanks for your effort.
But I am still uncertain so I think I will leave this challenge.

For example 5-th question.
quote: "Once you have chosen the start position for two of the three
normal rotors, how many possibilities are there for the start
position of the third rotor?"

Why so complicatedly stated?
I understand it as it is same as asking:
How many starting positions are there for a (normal) rotor?

The answer is too easy, so is it really asking this?

Re: Challenge  

  By: fretty on Oct. 2, 2011, 11:54 p.m.

Because this is not meant to be a boring textbook exercise, it is meant to be a challenge in combinatorics.

Whoever designed the challenge probably wanted people to think for themselves…writing the question in the way you stated it makes the answer completely obvious (not that the way it is actually stated doesn't, just makes it less obvious).


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