Codebusters C

Longivitis
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Re: Codebusters C

Post by Longivitis » September 25th, 2019, 9:42 pm

gz839918 wrote:
September 25th, 2019, 5:51 pm
jaggie34 wrote:
September 25th, 2019, 3:59 pm
Vortexx2 wrote:
September 25th, 2019, 2:13 pm
For the morbit code, are we given the key? I know we have to find the numbers based off of the key, but are we given what each of the numbers mean? Such as 1= . - , 2= -- , etc.?
I think we'd be given a keyword or part of a keyword, but it also could just be that we're given a few numbers
This appears to be right. Toebes' website has two sample prompts, one where some digits are given, and another where a keyword is revealed.
From the official rules, if we are given digits at least 6 of them must be given and we are given a keyword (state/nationals only btw) it must be at least 4 letters.

One reason why the suggested point values of pollux/morbit ciphers are low is because you can just eliminate some possibilities through morse and brute force the other solutions. I wouldn't recommend spending that much time on these because the morse code table is given, just know one x separates letters while two x's separates words.
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Re: Codebusters C

Post by MacintoshJosh » September 30th, 2019, 2:46 pm

Anyone have some good tips for solving patristocrats without any hints? Looking for word patterns and replacing letters based on frequency still fails on some problems for me. Patristocrats without hints are the one thing I'm terrified of...
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Longivitis
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Re: Codebusters C

Post by Longivitis » September 30th, 2019, 9:47 pm

MacintoshJosh wrote:
September 30th, 2019, 2:46 pm
Anyone have some good tips for solving patristocrats without any hints? Looking for word patterns and replacing letters based on frequency still fails on some problems for me. Patristocrats without hints are the one thing I'm terrified of...
There's a reason why a patristocrat without a hint is considered the hardest and therefore given the maximum amount of points if it is able to be solved. No spaces, and also no hints to be able to easily guess the letter frequency.

Honestly word patterns and checking frequency is almost always the best solution because there's a slight chance of revealing something. Other than that, plugging frequent letters (ETAOIN) could also be a mess because of the variability. If the quotes and solutions in the test happen to correlate to one another (it might happen depending on the test writer) than it can be somewhat easier to guess.

Besides, there's probably going to be at most one of them on the test so you shouldn't need to worry about them too much, a possibly strategy is to try to solve that one last so all of your teammates can work together. Focus more on the timed question and getting it early enough so that perhaps not being able to solve that pesky patristocrat wouldn't matter as much because of the bonus points from the timed question.
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Re: Codebusters C

Post by Nyerr » October 1st, 2019, 4:14 pm

Can some one help me figure out this question? Its from the 2019 Princeton Codebusters Exam.

Decrypt this message using the Vigenère cypher

G N G Q C K EV

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Re: Codebusters C

Post by jaggie34 » October 1st, 2019, 6:15 pm

Nyerr wrote:
October 1st, 2019, 4:14 pm
Can some one help me figure out this question? Its from the 2019 Princeton Codebusters Exam.

Decrypt this message using the Vigenère cypher

G N G Q C K EV
Do you have any hint?
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Re: Codebusters C

Post by Nyerr » October 1st, 2019, 6:32 pm

jaggie34 wrote:
October 1st, 2019, 6:15 pm
Nyerr wrote:
October 1st, 2019, 4:14 pm
Can some one help me figure out this question? Its from the 2019 Princeton Codebusters Exam.

Decrypt this message using the Vigenère cypher

G N G Q C K EV
Do you have any hint?
Nope. That's all they gave us. I have the answer key and everything i just dont know how they got that answer.

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Re: Codebusters C

Post by MacintoshJosh » October 1st, 2019, 6:38 pm

Nope. That's all they gave us. I have the answer key and everything i just dont know how they got that answer.
You sure that was all they gave you? I don't think solving a Vigenère without any hints or a crib is even possible. The key could be literally anything...
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Re: Codebusters C

Post by Nyerr » October 1st, 2019, 6:42 pm

MacintoshJosh wrote:
October 1st, 2019, 6:38 pm
Nope. That's all they gave us. I have the answer key and everything i just dont know how they got that answer.
You sure that was all they gave you? I don't think solving a Vigenère without any hints or a crib is even possible. The key could be literally anything...
You actually can by figuring out what the key is by looking for coincidences between rows of shifts...et cetera. Theres a good video by Theoretically that explains it well. But yea. Just that ciphertext with nothing else.

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Re: Codebusters C

Post by knightmoves » October 1st, 2019, 6:55 pm

Nyerr wrote:
October 1st, 2019, 6:42 pm
You actually can by figuring out what the key is by looking for coincidences between rows of shifts...et cetera. Theres a good video by Theoretically that explains it well. But yea. Just that ciphertext with nothing else.
Not with 8 letters of cyphertext, you can't. Sure, with a long cyphertext you can break Vigenere with frequency analysis techniques, but if all you have is an 8 letter cyphertext, your key could easily be 8 letters, and what you have is an encryption with an unknown one-time pad. By construction, that is unbreakable.

Sure - you could guess an 8 letter answer (Olympiad, perhaps) but all answers are achievable.

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Re: Codebusters C

Post by Nyerr » October 1st, 2019, 6:57 pm

knightmoves wrote:
October 1st, 2019, 6:55 pm
Nyerr wrote:
October 1st, 2019, 6:42 pm
You actually can by figuring out what the key is by looking for coincidences between rows of shifts...et cetera. Theres a good video by Theoretically that explains it well. But yea. Just that ciphertext with nothing else.
Not with 8 letters of cyphertext, you can't. Sure, with a long cyphertext you can break Vigenere with frequency analysis techniques, but if all you have is an 8 letter cyphertext, your key could easily be 8 letters, and what you have is an encryption with an unknown one-time pad. By construction, that is unbreakable.

Sure - you could guess an 8 letter answer (Olympiad, perhaps) but all answers are achievable.
Olympiad was actually the answer! You're right, thats the issue i encountered. So why would they put an unsolvable question on a test? Or are they testing how clever we are...

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