Codebusters B/C

[Sorrow2]

Memorize the Baconian alphabet and grind. I don't know anything about Xenos so I can't help you there, but this event is literally just practice and there isn't a way around that. No shortcuts

sad

[hmmm]

If we get less than 2 mistakes on a Special Bonus Question or the Timed Question are we supposed to get the Bonus Points?

I believe so. More than 2 errors means you get penalty points, and you don't get the bonus.

[gz839918]

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

(Sorry for the delay! I'm bumping your post because it got buried in the post approval process. Welcome to Scioly.org!)

John Toebes created Codebusters, and as long as he's still around, it's possible it may continue. I'm not too sure of anything though, since I'm not tapped into nationals nor do I know Toebes too well.

[Sorrow2]

What if on the timed question what if you do the thing the paper asks you to do at last second? does it still count??????/

[bangtanarmy7]

What if on the timed question what if you do the thing the paper asks you to do at last second? does it still count??????/

You would still get full points for the question, but you wouldn't get the extra bonus points for solving it in the first 10 mins.

[Umaroth]

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

Hello, now that the tentative event slate for next year is out, it appears that Codebusters is sticking around. I'd expect ciphers swapping in and out, but the core of the event staying the same (aristos, timed question, etc.)

[Mythic]

Hello, I was wondering if someone could explain how you solve the Cryptanalysis of an Affine.

[knightmoves]

Hello, I was wondering if someone could explain how you solve the Cryptanalysis of an Affine.

Here's a worked example for you. You are given the cyphertext
"ABOBRFLYBMLHGQBPSLYLSSRYBTODGWLYLQDFRF", and told that the first two letters of the plaintext are H and E.

So you know that under the affine encryption, E(4) -> B(1) and H(7) ->A (0).

So (4a + b) mod 26 = 1
and (7a + b) mod 26 = 0

Subtracting these, you get 3a mod 26 = -1 = 25.

So we're hunting for a value of a for which 3a mod 26 = 25.
3a = 25 is no good, 'cause a needs to be an integer.
3a = 51 gives a = 17, which is a viable solution.
3a = 77 doesn't have an integer solution, and then there aren't any other valid solutions, because you know a<26.

So with a=17, the first equation becomes
(68 + b) mod 26 = 1
or equivalently
(16 + b) mod 26 = 1

And so b = 11.

Now you have determined a and b, you can compute the mappings.
A(0) -> (b mod 26) = 11 = L
B(1) -> (a + b) mod 26 = 2 = C
C(2) -> (2a + b) mod 26 = 19 = T
D(3) -> (3a + b) mod 26 = 10 = K.

And so on.

You might prefer to compute the mappings for the high frequency letters (etaoin shrdlu...) rather than doing them in alphabetical order. Finishing this off is left as an exercise for the reader

[Mythic]

Hi, quick question what operations can you get for a cryptarithm in states?

[knightmoves]

Hi, quick question what operations can you get for a cryptarithm in states?

There is no restriction in the rules. So in theory, the answer is "any mathematical operation that B team members can be assumed to be familiar with". Which would probably be addition, subtraction, multiplication, division, square roots and small integer powers.

The rules don't actually specify that the cryptarithm has to be in base 10, but it would be a particularly evil ES who would compose a problem in any other base.