BE wrote:
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.

Thank you for your quick reply. This is possibly the reason why I failed to submit an answer. But in the description of the challenge it has been nowhere mentioned, that it have to be exactly 100 of every kind of cipher (there is no reason that it should be exactly 100 of every kind). And when Cipher Id was a level III challenge it was not necessary to enter exactly 100 of every kind of cipher and it was also possible to enter other characters than S, C, P, V and H (for instance X for a still unknown cipher). I don't know, if this is still possible in the level II challenge or if only the five letters S, C, P, V and H are now allowed.

Anyway, the behaviour of the solution checking routine has changed without telling it to the solvers. This is a little disturbing at least for the solvers who had already worked on the level III variant of these challenge.

But in the description of the challenge it has been nowhere mentioned, that it have to be exactly 100 of every kind of cipher.

This is not really true. Page 2 of the challenge template states that the "500 ciphertext messages comprise 100 ciphertexts from each of the following [[5]] classic ciphers".

Anyway, the behaviour of the solution checking routine has changed without telling it to the solvers.

When we moved this challenge from level III to level II we changed the evaluation routine as the answers before could be used for a clever brute-force trial-and-error way of finding the solution which didn't even need to look at the ciphers (it was our fault that we didn't think about that in advance). Nevertheless, the solution is exactly the same as it was before. As 6 people already solved the challenge as level II challenge in the meantime I am sure you will do so too.

If you need more information please send me an email.

BE wrote:
This is not really true. Page 2 of the challenge template states that the "500 ciphertext messages comprise 100 ciphertexts from each of the following [[5]] classic ciphers".

Yes you are right. I have overlooked this. Sorry.
I was able to solve the challenge now.

Can someone please elaborate about how the Vigenere
ciphers are broken? And whether they are still broken
after the rerelease of the challenge?

EDIT
Nevermind, I finished it and found only one Vig cipher with any errors.

My best submission has 498 out of 500 ciphers identified correctly, i.e. two characters are swapped compared to the correct result string (of course, my submitted string has 100 each of H, S, V, C and P). I'm at a loss regarding how to proceed now. I spent a lot of time coming this far and so re-checking every single cipher would take far too much time, especially because my program for the Hill cipher is rather slow (I'm doing everything in Python).

Does anyone have a hint? Thanks a lot!

Peter