Codebusters C

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Re: Codebusters C

Post by Name » October 1st, 2019, 7:57 pm

Nyerr wrote:
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...
whoever wrote it probably forgot to mention the key in the hint.
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Re: Codebusters C

Post by Nyerr » October 1st, 2019, 8:13 pm

Name wrote:
October 1st, 2019, 7:57 pm
Nyerr wrote:
October 1st, 2019, 6:57 pm
knightmoves wrote:
October 1st, 2019, 6:55 pm


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...
whoever wrote it probably forgot to mention the key in the hint.
I was thinking that - but also Princeton.

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Re: Codebusters C

Post by jaggie34 » October 2nd, 2019, 8:17 am

Nyerr wrote:
October 1st, 2019, 8:13 pm
Name wrote:
October 1st, 2019, 7:57 pm
Nyerr wrote:
October 1st, 2019, 6:57 pm

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...
whoever wrote it probably forgot to mention the key in the hint.
I was thinking that - but also Princeton.
We could reverse engineer the key and see if it's anything meaningful?
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Re: Codebusters C

Post by Nyerr » October 2nd, 2019, 8:47 am

jaggie34 wrote:
October 2nd, 2019, 8:17 am
Nyerr wrote:
October 1st, 2019, 8:13 pm
Name wrote:
October 1st, 2019, 7:57 pm

whoever wrote it probably forgot to mention the key in the hint.
I was thinking that - but also Princeton.
We could reverse engineer the key and see if it's anything meaningful?
The key was "SCIENCES". I got that, but nothing was given other than ciphertext

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Re: Codebusters C

Post by Longivitis » October 2nd, 2019, 11:25 am

Nyerr wrote:
October 2nd, 2019, 8:47 am
jaggie34 wrote:
October 2nd, 2019, 8:17 am
Nyerr wrote:
October 1st, 2019, 8:13 pm

I was thinking that - but also Princeton.
We could reverse engineer the key and see if it's anything meaningful?
The key was "SCIENCES". I got that, but nothing was given other than ciphertext
That was probably a mistake from the test writer considering the other questions look fine... but given the point value I think this was on purpose, which is interesting because I don't believe anyone could have guessed that.
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Re: Codebusters C

Post by knightmoves » October 3rd, 2019, 6:43 am

Longivitis wrote:
October 2nd, 2019, 11:25 am
That was probably a mistake from the test writer considering the other questions look fine... but given the point value I think this was on purpose, which is interesting because I don't believe anyone could have guessed that.
Well, I did guess it on the previous page. Olympiad was the most obvious 8 letter word that was connected to the event, and that's how people who think they are cute tend to think. (Princeton is 9 letters, otherwise that might have been a candidate). Some people love to ask the "guess what I'm thinking" question - they ask a vague open-ended type question with many possible reasonable answers, but only consider the answer that they thought of as "correct" and every other true statement is "wrong". I have strong words for how I feel about those people, and I probably shouldn't use them on this forum.

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Re: Codebusters C

Post by Umaroth » October 3rd, 2019, 4:49 pm

knightmoves wrote:
October 3rd, 2019, 6:43 am
Longivitis wrote:
October 2nd, 2019, 11:25 am
That was probably a mistake from the test writer considering the other questions look fine... but given the point value I think this was on purpose, which is interesting because I don't believe anyone could have guessed that.
Well, I did guess it on the previous page. Olympiad was the most obvious 8 letter word that was connected to the event, and that's how people who think they are cute tend to think. (Princeton is 9 letters, otherwise that might have been a candidate). Some people love to ask the "guess what I'm thinking" question - they ask a vague open-ended type question with many possible reasonable answers, but only consider the answer that they thought of as "correct" and every other true statement is "wrong". I have strong words for how I feel about those people, and I probably shouldn't use them on this forum.
They also did that on their Codebusters trial event test from two years ago. They gave an 8 letter Vigenere without a key, which we later figured out to be Princeto(n).
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Re: Codebusters C

Post by someone1580 » October 5th, 2019, 9:25 pm

What would be your recommended order of which ciphers to work on first?

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Re: Codebusters C

Post by Name » October 5th, 2019, 10:29 pm

someone1580 wrote:
October 5th, 2019, 9:25 pm
What would be your recommended order of which ciphers to work on first?
The timed cipher. After that whatever you feel like you can solve quickly while also being the most points. That really depends on the person. IMO Aristocrats are always reliable, and patristocrat/xenocrypts should be attempted if you can solve them semi reliably.
Not too familiar with morbit and pollux, but I'd say probably don't do them first, they look like they'd take forever because you have to double decode them (numbers to morse to English) and probably won't be worth that much. RSA (at least the questions that rely on rapid modular exponentiation or extended euclidean algorithm), while probably worth alot take too long and IMO shouldn't be attempted first because one mistake and you lose all points (with these crappy 4 function calcs you can't even check your answers)
But just in general, do whatever you're comfortable with I guess.
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Re: Codebusters C

Post by will0416 » October 6th, 2019, 2:51 pm

someone1580 wrote:
October 5th, 2019, 9:25 pm
What would be your recommended order of which ciphers to work on first?
I’d go hard to easy. You can fly through aristocrats later in the test when you’re in a time crunch (and you won’t need to check your work) but you want to make sure you’ve got the math completely right early on in something like a 3x3 hill or rsa.
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