Codebusters C

will0416
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Re: Codebusters C

Post by will0416 » April 5th, 2019, 12:03 pm

l0lit wrote:
will0416 wrote:Anyone got higher level tips for the TQ? We currently average in the 1:40's but I'm assuming that we'll be a bit slower at tournaments to come (I'd say our slowest recent time has been 2:30 and we want to prevent that from happening in a high-stakes scenario).
Can you send a sample timed question you took for length? Strategies vary based on how long the timed question is.
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I don't think this is the best example as we didn't really struggle on this one (I think 1:46?) but I forgot what tests we took and couldn't find the file to one of them to get a better quote. There are some pretty obvious word patterns to go off of but I meant in more obscure circumstances without a clear path to follow. Sorry for the late response (lol and the vague description below).

i.e. something without familiar patterns/contractions/words after a comma that can be obvious/whatever else there may be
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Re: Codebusters C

Post by WangwithaTang » April 5th, 2019, 7:03 pm

Can somebody explain how to do the following? Letter frequency analysis isn't working and using word predictions isn't helping either. The first is an aristocrat, the second is a Spanish xenocrypt, and the third is a patristocrat. (They're from the University of Florida practice test)

QD QFFSY Q RQZ AYYFK MPY RGWMGL QNQZ.

AY LAYZW AD JYGD EFD CLGDQ VL SLQDL SD LMFJL DO VL
DRGFDVL.

8) Decrypt the following Patristocrat where the ciphertext letters “QPP” decrypt to “TOO”
[450 Points].
TUYXUQPPWPAWUXAUSYHPVQLPTOVWLOPAUCTULYEUYASAP
QYHPVQLPTLYJJCTUYXU

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Re: Codebusters C

Post by pepperonipi » April 5th, 2019, 9:02 pm

I can help with the first one.
WangwithaTang wrote:Can somebody explain how to do the following? Letter frequency analysis isn't working and using word predictions isn't helping either. The first is an aristocrat, the second is a Spanish xenocrypt, and the third is a patristocrat. (They're from the University of Florida practice test)

QD QFFSY Q RQZ AYYFK MPY RGWMGL QNQZ.
First, we see that Q is a single-letter, meaning that it's probably A or I. Given that there aren't too many words that would be I _ I _ (the last word with I substituted in) or I_ _ _ _ (the second word with I substituted in), we can assume that Q is A:

AD AFFSY A RAZ AYYFK MPY RGWMGL ANAZ

Second, see that last word? A _ A _ is probably AWAY, so let's fill that in.

AD AFFSY A RAY AYYFK MPY RGWMGL AWAY

Third, let's try MPY as "THE." It's likely, so it's worth a shot:

AD AFFSE A RAY AEEFK THE RGWTGL AWAY

Fourth, at this point, we can say the second word is likely "APPLE." (What other words would fit this letter sequence?)

AD APPLE A RAY AEEPK THE RGWTGL AWAY

Now, you can probably see that this is:

AN APPLE A DAY KEEPS THE DOCTOR AWAY

Hope this helps!
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Re: Codebusters C

Post by jimmy-bond » April 8th, 2019, 8:01 pm

Can someone tell me why proctors believe that no-hint K1 encoded patristocrats are easier than K2 patristocrats with the keyword? I mean the type of alphabet is basically useless without a keyword. At states, the K2 was worth twice as much as the K1 and I wanna know why. Does anyone feel that no-hint K1s are easier than K2s with the keyword? And if so, how do?
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Re: Codebusters C

Post by Name » April 8th, 2019, 8:09 pm

jimmy-bond wrote:Can someone tell me why proctors believe that no-hint K1 encoded patristocrats are easier than K2 patristocrats with the keyword? I mean the type of alphabet is basically useless without a keyword. At states, the K2 was worth twice as much as the K1 and I wanna know why. Does anyone feel that no-hint K1s are easier than K2s with the keyword? And if so, how do?
Could just be the difficulty of the quote itself.
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Re: Codebusters C

Post by OrigamiPlanet » April 16th, 2019, 1:25 pm

So states is coming up in PA, but I'm still very confused as to how the crib word is supposed to be utilized when doing cryptanalysis of a vigenere. I've looked online for a while now, but I keep getting the kasiski method, and while I do believe it is a very good idea to use, I still have no clue as to how the crib plays a part in all of this. Is it truly just a confirmation that you have been doing it correctly, or is there another method?
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Re: Codebusters C

Post by pepperonipi » April 16th, 2019, 4:36 pm

OrigamiPlanet wrote:So states is coming up in PA, but I'm still very confused as to how the crib word is supposed to be utilized when doing cryptanalysis of a vigenere. I've looked online for a while now, but I keep getting the kasiski method, and while I do believe it is a very good idea to use, I still have no clue as to how the crib plays a part in all of this. Is it truly just a confirmation that you have been doing it correctly, or is there another method?
Honestly, I had no idea what the Kasiski method was and after briefly looking at it, I can say that it doesn't seem like much fun.

For a Vigenère Cipher, just remember that (PT + KEY) mod 26 = CT, which means that CT - PT = KEY mod 26. This applies for all letters. So if you are given the first three words, then repeatedly use PT - CT = KEY, and you should start to find a pattern. Then, you can use your new-found key to solve the rest of the cipher.

For example, solve "Vvlw kg ksy W vsnjh xjsvi ewslgfv," where the first three words are "This is how":

First, T (=19) encrypts to V (=21), so we can find that KEY = 21 - 19 = 2, meaning that the first letter of our key is "C"
Second, H (=7) encrypts to V (=21), so we can find that KEY = 21 - 7 = 14, meaning that the second letter of our key is "O"
Repeating this process, we get:
CODECODEC

You can clearly see that the key is "CODE," which we can use to solve our cipher. Using this key gives us: "This is how I solve these ciphers."

I hope I am understanding your question right.
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Re: Codebusters C

Post by will0416 » May 5th, 2019, 6:31 pm

Has anyone seen any particularly memorable varieties of encoding Baconian ciphers that have a decent chance of appearing on an official test (i.e. methods other than odd/even, vowel/consonant, letters from one word/letters from a different word)?
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Re: Codebusters C

Post by Anomaly » May 6th, 2019, 2:00 pm

will0416 wrote:Has anyone seen any particularly memorable varieties of encoding Baconian ciphers that have a decent chance of appearing on an official test (i.e. methods other than odd/even, vowel/consonant, letters from one word/letters from a different word)?
On our regionals test, we had something uses a bunch of symbols like !@#$%^&*()
I never actually figured out what the pattern was though, it might have been all the symbols on the odd numbers of a keyboard / symbols on even numbers of keyboard
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Re: Codebusters C

Post by will0416 » May 6th, 2019, 3:02 pm

Anomaly wrote:
will0416 wrote:Has anyone seen any particularly memorable varieties of encoding Baconian ciphers that have a decent chance of appearing on an official test (i.e. methods other than odd/even, vowel/consonant, letters from one word/letters from a different word)?
On our regionals test, we had something uses a bunch of symbols like !@#$%^&*()
I never actually figured out what the pattern was though, it might have been all the symbols on the odd numbers of a keyboard / symbols on even numbers of keyboard
Oh that sounds pretty clever. I think I've also seen American currency vs. foreign currencies (maybe British) on a test before but there have been some Baconians that have just seemed impossible.
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