Codebusters C

WangwithaTang
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Re: Codebusters C

Postby WangwithaTang » March 25th, 2019, 7:31 pm

Can somebody please explain this event? It just got released to division B and I don't really understand how it works.

UTF-8 U+6211 U+662F
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Re: Codebusters C

Postby UTF-8 U+6211 U+662F » March 25th, 2019, 7:34 pm

WangwithaTang wrote:Can somebody please explain this event? It just got released to division B and I don't really understand how it works.

Not sure if your rules are different, but basically you get a list of bunch of ciphers that you're expected to either decode, encode, or both. Usually the type of cipher is specified. Check the Wiki for more details and Test Exchange for example problems.

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Re: Codebusters C

Postby wec01 » March 25th, 2019, 7:37 pm

UTF-8 U+6211 U+662F wrote:
WangwithaTang wrote:Can somebody please explain this event? It just got released to division B and I don't really understand how it works.

Not sure if your rules are different, but basically you get a list of bunch of ciphers that you're expected to either decode, encode, or both. Usually the type of cipher is specified. Check the Wiki for more details and Test Exchange for example problems.

You can also practice through the question marathon if you want, although it's not entirely reliable in terms of how active it is.
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Re: Codebusters C

Postby starfruit » March 25th, 2019, 8:06 pm

wec01 wrote:
UTF-8 U+6211 U+662F wrote:
WangwithaTang wrote:Can somebody please explain this event? It just got released to division B and I don't really understand how it works.

Not sure if your rules are different, but basically you get a list of bunch of ciphers that you're expected to either decode, encode, or both. Usually the type of cipher is specified. Check the Wiki for more details and Test Exchange for example problems.

You can also practice through the question marathon if you want, although it's not entirely reliable in terms of how active it is.

I compete in this event for Division B. The rules are pretty much the same, but we don't have to know Hill Cipher, RSA, Affine Analysis, and Affine decryption. What you do need to know is Aristocrats, Patristocrats, Baconian, Affine encryption, Atbash, Caesar Cipher, Xenocrypts, Vigenere, and Running Key Cipher (I think that's it?). You don't have notes for this event, so memorize! The test format can vary, but it always starts off with a timed question. You can get bonus points based on how fast you answer. The rest of the test is just cracking the rest of the codes. Definitely go read your rules!
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Re: Codebusters C

Postby WangwithaTang » March 27th, 2019, 9:17 am

starfruit wrote:
wec01 wrote:
UTF-8 U+6211 U+662F wrote:Not sure if your rules are different, but basically you get a list of bunch of ciphers that you're expected to either decode, encode, or both. Usually the type of cipher is specified. Check the Wiki for more details and Test Exchange for example problems.

You can also practice through the question marathon if you want, although it's not entirely reliable in terms of how active it is.

I compete in this event for Division B. The rules are pretty much the same, but we don't have to know Hill Cipher, RSA, Affine Analysis, and Affine decryption. What you do need to know is Aristocrats, Patristocrats, Baconian, Affine encryption, Atbash, Caesar Cipher, Xenocrypts, Vigenere, and Running Key Cipher (I think that's it?). You don't have notes for this event, so memorize! The test format can vary, but it always starts off with a timed question. You can get bonus points based on how fast you answer. The rest of the test is just cracking the rest of the codes. Definitely go read your rules!

okay, thanks guys!

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Re: Codebusters C

Postby will0416 » March 28th, 2019, 6:04 am

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).
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Re: Codebusters C

Postby l0lit » March 28th, 2019, 8:46 am

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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Re: Codebustews C

Postby WangwithaTang » April 1st, 2019, 8:28 am

Ok, can somebody explain how to do the crib method for Vigenere Ciphers?

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Re: Codebustews C

Postby dragonfruit35 » April 2nd, 2019, 2:05 am

WangwithaTang wrote:Ok, can somebody explain how to do the crib method for Vigenere Ciphers?


Basically, a crib is a portion of the plaintext, so if you're given, say, the first three words already decrypted, then you would line those up with the ciphertext and subtract the plaintext letter values (be sure to use A=0) from the ciphertext letter values, which should result in the letter values of the key used to encrypt the cipher once you've gone through enough plaintext-ciphertext letter pairs. Once you've found the key, you can just copy it down over the rest of the ciphertext and solve normally.

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Re: Codebustews C

Postby WangwithaTang » April 2nd, 2019, 3:50 pm

dragonfruit35 wrote:
WangwithaTang wrote:Ok, can somebody explain how to do the crib method for Vigenere Ciphers?


Basically, a crib is a portion of the plaintext, so if you're given, say, the first three words already decrypted, then you would line those up with the ciphertext and subtract the plaintext letter values (be sure to use A=0) from the ciphertext letter values, which should result in the letter values of the key used to encrypt the cipher once you've gone through enough plaintext-ciphertext letter pairs. Once you've found the key, you can just copy it down over the rest of the ciphertext and solve normally.

oh, okay, thanks!

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Re: Codebusters C

Postby 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

Postby 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

Postby 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

Postby 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

Postby 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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