Codebusters C

WangwithaTang
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Re: Codebusters C

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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

Post by 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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WangwithaTang
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Re: Codebustews C

Post by 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

Post by 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

Post by 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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