Codebusters B/C

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RasmitDevkota
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Re: Codebusters B/C

Post by RasmitDevkota »

cyberdoggo wrote: December 21st, 2022, 5:48 pm
Somebody11 wrote: December 7th, 2022, 7:38 am Where can I find an as-easy-as-possible explanation of how to decrypt an Affine cipher with key? I am pretty confused with the math.
to decrypt affine cipher, you need 3 values. a, b, and t. the decryption formula is t(x-b) mod26.
the easiest way to look at it is to see t as a^-1, where at mod26 has to equal 1.
to find the value of t, just use a.
for example, let's say a = 7 and b = 39.
to find 7t mod26 = 1, you just have to try every value. in this case, t = 15.
therefore, your decryption formula in this case would be 15(x-39) mod26.
hope that helps.
One tiny but significant thing to mention - you don't have to try every value, the inverses mod 26 of all the numbers that can be your value appear in the reference sheet, it's the two-row table on the first page, where each column is a pair of inverses.

Also, as a general recommendation - the Scioly.org Wiki page for Codebusters has great explanations of most ciphers, both decoding and encoding (where applicable). It's not perfect or comprehensive but it's the best first place to check!
Last edited by RasmitDevkota on December 22nd, 2022, 7:27 pm, edited 1 time in total.
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Re: Codebusters B/C

Post by pumptato-cat »

How do you guys solve Morbit/Pollux/Baconian on Scilympiad? I'm copying the problem down on paper and it takes way too long.
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Re: Codebusters B/C

Post by chioneg »

Does anyone know whether the Morse Code portion is using International Morse Code or American Morse Code?
Thanks in advance!
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Re: Codebusters B/C

Post by pumptato-cat »

Morse Code ciphers use the International Morse Code alphabet.
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Re: Codebusters B/C

Post by Sorrow2 »

Does anyone know how to do pollux, fractionated morse code cipher and morbit?
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Re: Codebusters B/C

Post by Sorrow2 »

Sorrow2 wrote: February 15th, 2023, 10:29 am Does anyone know how to do pollux, fractionated morse code cipher and morbit?
also baconian i think those are on my state tournament.
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Codebusters returning?

Post by PBJSandwich »

Hello friends, first post here. I am wondering whether Codebusters will be returning for 2024 and 2025. The event has repeated for 5 times in a row which is quite an amount for a repeating event. Will next year mark its death?

https://scioly.org/wiki/index.php/Past_Event_Rotations
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Re: Codebusters B/C

Post by bangtanarmy7 »

Sorrow2 wrote: February 15th, 2023, 10:29 am Does anyone know how to do pollux, fractionated morse code cipher and morbit?
so for most of the ciphers, I use this https://www.youtube.com/@nancywang5952/featured channel, and this girl explains the basics really well, as well as shortcuts for some of the ciphers.
Last edited by bangtanarmy7 on February 17th, 2023, 11:47 am, edited 1 time in total.
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Re: Codebusters B/C

Post by randomdogonapc »

Haven’t posted on this particular forum yet, but just wanted to ask about some people’s strategies. It seems impossible to do the harder ciphers consistently(patristocrats, Cryptarithms, etc.). Pollux ciphers and Morbit ciphers are some of the easier and reliable ciphers, while aristocrats are not very consistent but still the most common cipher. The low point ciphers(Caesar and Atbash) are usually easy and our team has gone for them on every invitational. What ciphers are you guys prioritizing and which are you guys skipping?

Also, does anybody know how to use the alphabet square provided on tests? They have half of the alphabet instead of the full one used on regular alphabet squares used for vigenere/Porta cipher.
Last edited by randomdogonapc on February 18th, 2023, 3:54 pm, edited 1 time in total.
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Re: Codebusters B/C

Post by Mythic »

If we get less than 2 mistakes on a Special Bonus Question or the Timed Question are we supposed to get the Bonus Points?
Last edited by Mythic on February 19th, 2023, 5:59 pm, edited 1 time in total.
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