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Challenge "Cipher ID — Part 1"

Challenge "Cipher ID — Part 1"  

  By: admin on Nov. 10, 2019, 2:43 p.m.

Determine which type of classic cipher was used to generate each of 500 ciphertext messages. The ciphers used in this challenge are simple substitution, columnar transposition, Vigenère, Playfair, and Hill.
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 Last edited by: admin on Oct. 31, 2021, 2:55 a.m., edited 12 times in total.

Re: Challenge  

  By: Yokozuna on Nov. 14, 2019, 3:34 p.m.

I find it is not ok to change the conditions for these challenge suddenly four days after publishing it (maximal 20 attempts instead of 99 attempts four days before). I made my 17 attempts because I knew that I have 99 attempts in the maximum. If I know from the beginning that I have only 20 attempts, then I would have considered another approach. Now with only three attempts left my chances to solve this challenges are going to null. This is not funny at all!

Re: Challenge  

  By: vexilla72 on Nov. 14, 2019, 6:51 p.m.

I find it is not ok to change the conditions for these challenge suddenly four days after publishing it (maximal 20 attempts instead of 99 attempts four days before). I made my 17 attempts because I knew that I have 99 attempts in the maximum. If I know from the beginning that I have only 20 attempts, then I would have considered another approach. Now with only three attempts left my chances to solve this challenges are going to null. This is not funny at all!

Yokozuna, I entirely agree with you !
I also tested because we had 99 attempts and now, what a bad surprise !
I hope the number of attempts will be back to the 99 ones.

Re: Challenge  

  By: D3d4lu5 on Nov. 14, 2019, 9:39 p.m.

There are some cipher texts that look pretty weird.

For example no 105 is:

"qddqfmsqdaqoukvqccusudujcqbycwmvxmrbhoilethereadertobecomegenuinelyabsorbedinwhatissaidwhetherheresp"

where the last 61 characters are plain text.

I don't think that any of these ciphers can produce such a cipher text.

Re: Challenge  

  By: Yokozuna on Nov. 15, 2019, 6:22 a.m.

Disappointing! No answer from the administration. I am going offline because I had to leave now.

@D3d4lu5:

You are right, this looks strange, but Bart13 has solved it anyway.

Re: Challenge  

  By: vexilla72 on Nov. 15, 2019, 11:20 a.m.

Today the challenge has changed from Level 3 to Level 2.
Yesterday, I had any attemps left.
Now, it is written that I have not anymore attempt ?
Was 99 -> 20 but now ???

I do not understand such a change !

Re: Challenge  

  By: D3d4lu5 on Nov. 15, 2019, 5:35 p.m.

I guess there is an issue with the cipher texts that belong to the Vigenère Cipher.

It is neither a classical Vigenère nor an autokey cipher.

Nevertheless, the challenge is solvable, but it does not match the challenge description.

Re: Challenge  

  By: Veselovský on Nov. 16, 2019, 1:17 p.m.

Why I cannot submit my solution?
Leave the challenge as it is and make another one corrected.
People spent time on solving this challenge. Do they have to spend more everytime you change the challenge?

It is also strange how the level was changed.
With purported standard Vigenère it was level III.
With unaware defective Vigenère, which makes it harder to solve, it was changed to level II.

Re: Challenge  

  By: rcll0891 on Nov. 16, 2019, 6:04 p.m.

Irgendetwas stimmt hier nicht. Bei mir steht ebenfalls, dass ich keinen Versuch mehr habe, obwohl ich noch keine einzige Lösung übermittelt habe. [HTML_REMOVED]

Re: Challenge  

  By: Bart13 on Nov. 17, 2019, 8:41 p.m.

I think I should make an apology to everyone who has spent time solving this challenge and now can't enter the solution because it is being reworked as I feel that I am (at least partially) responsable for that.

Actually I solved it twice in two different ways.
One way lead to the reduction of 100 attempts to 20.
The other lead to the change of level III to level II.

I do not agree with Veselovský that the faulty Vigenère encryption makes the challenge more difficult to solve.
My second method actually benefited from the wrong encryption.

Re: Challenge  

  By: Veselovský on Nov. 17, 2019, 9:46 p.m.

I do not agree … that the faulty Vigenère encryption makes the challenge more difficult to solve

The difficulty in this case depends on what type of solver you are. Whether you trust everything that is written in the description of challenges or you doubt and verify everything yourself. I personally think the correct Vigenère would make it easier for many solvers, because methods to solve or identify it are already known and you do not have to think too much about it.

I realized that the Vigenère was not correct too, but It took me some time to identify the error and then to adapt my algorithms. Was it correct I think I would have solved it more quickly.

I think I should make an apology … Actually I solved it twice in two different ways.

I do not think you should have to apologize for anything. There are always several different ways to solve anything.

Re: Challenge  

  By: tryone144 on Nov. 19, 2019, 1:48 p.m.

We apologize for the error in the Vigenère ciphertexts and the tempory decommission (we had tested only the beginnings of the received ciphertexts and they had been correct).
Thanks to Bart13 for pointing us to the mistake. We then contacted the author and he fixed it. The corrected challenge is now available again.

@Yokozuna, @vexilla72, …:
For those who have not solved it yet, the used attempts are reset.
And the starting time is set to the new release date, so that you can still get the maximum number of points (despite the temporary interruption).

The fact that it was first rated at level 3 was due to our wrong assessment of the level of difficulty. We will build a part 2 soon that will really fit into level 3.

Thank you all for your replies and help, and sorry again.

Re: Challenge  

  By: Yokozuna on Nov. 23, 2019, 1:42 a.m.

I have already entered three answers to no avail. The first time I got no answer at all (neither right or wrong nor the number of wrong characters) . After the next two trials I have got the hint that the answer has the wrong format. I entered 500 upper-case letters each time. Can somebody please check what is going wrong.

Re: Challenge  

  By: Yokozuna on Nov. 23, 2019, 11:06 a.m.

In addition to my last post I want to make some more remarks.

In the past we had already problems submitting the answer with a lot of challenges. This was sometimes due to the description of the challenge which did not state clearly enough how to enter the solution correctly. But sometimes there might occur some misfortune, for instance, that some unwanted (maybe invisible to the solver) characters like carriage return or other stuff like this enters the answer string (for instance by copy and paste) unrecognised by the solver and that the algorithm for checking the answer therefore can not recognize the format of the answer.

In the past the solver got in this cases only a 'red face' and he thought that his answer is wrong but, disregarding a possible formatting issue, the answer of the solver might have been possibly correct. Therefore it is important that the solver will be informed, that a formatting issue exists (as with the challenge Cipher ID - Part 1).

But even worse, in addition the solver has been punished by reducing the number of possible answers. The solver should not be punished this way because the formatting problem might not be in his responsibility.

After submitting a possible answer the input window together with it content disappears. Therefore the solver has in case of a 'red face' no possibility to check his input himself (for instance for a formatting issue). It would be nice, that the entered answer is still available in a input window after submitting it, especially in the case of a formatting problem.

In my first trial for this challenge I had a very strange behavior of the system. I had a view, where all challenges will be displayed in order of its publishing date. After pressing the submit button the view disappeared and I got a view with only the Cipher Id challenge and with a open and empty input window. There was no 'red face' and no hint to a formatting problem. At first I thought, that the system has not recognized my answer at all, but then I realized, that the number of possible answers have been reduced already by one.

In the other two trials I entered the answer the same way as I did, when these challenge was a level III and I had no problems entering answers, when it was a level III.

Therefore it would be nice to restore my number of possible solutions.

Re: Challenge  

  By: be on Nov. 23, 2019, 11:45 a.m.

In addition to my last post I want to make some more remarks.

Thanks for your constructive suggestions. We think about how to implement them.

One thing we quickly can do is filter out all white space characters in the submitted solution before doing the evaluation – this also will reduce the rejections with the wrong format statement.

Especially for the CipherID – Part 1 challenge, the format warning also appears if there are not exactly 100 lettes of each of the 5 possible values in the solution string. This might have been the case in your first post. Maybe we should make MTC3 report this reason back explicitely.


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