Codebusters C

[sciencenerd101]

Hello, I have been having trouble learning affine cipher and was wondering if there was any resources that you guys would recommend to learn this code?

[Name]

Hello, I have been having trouble learning affine cipher and was wondering if there was any resources that you guys would recommend to learn this code?

https://crypto.interactive-maths.com/affine-cipher.html has a good explanation of how to encode or decode
https://www.cs.uri.edu/cryptography/classicalaffine.htm also explains it, and also how to solve affines with a crib

[TheWood]

What would be your recommended order of which ciphers to work on first?

I’d go hard to easy. You can fly through aristocrats later in the test when you’re in a time crunch (and you won’t need to check your work) but you want to make sure you’ve got the math completely right early on in something like a 3x3 hill or rsa.

I disagree with this, at least for the way that I've been approaching codebusters. For code, you're almost definitely going to have leftover questions. Attempting the harder problems first leads to the risk of you spending a lot of time on that question and then still not solving it. Though with practice, RSA and 3x3 hill cipher questions can become relatively easy.

[codewinorbust]

What would be your recommended order of which ciphers to work on first?

I’d go hard to easy. You can fly through aristocrats later in the test when you’re in a time crunch (and you won’t need to check your work) but you want to make sure you’ve got the math completely right early on in something like a 3x3 hill or rsa.

I disagree with this, at least for the way that I've been approaching codebusters. For code, you're almost definitely going to have leftover questions. Attempting the harder problems first leads to the risk of you spending a lot of time on that question and then still not solving it. Though with practice, RSA and 3x3 hill cipher questions can become relatively easy.

it is harder, but id say (especially for weaker teams) trying stuff like RSA and 3x3 hill is good because its a lot of points and a gauranteed solve. sometimes, trying xenocrypts or patristocrats don't get you anywhere and those are the biggest wastes of time

[jlamslam]

Hi, kind of similar to the questions previously asked, but what is the best way to manage time?

I ask this because of the following scenario that happened at state last year: We break up the test, so everyone is working on their own cipher. When there are 5 minutes left, we check progress. We figured out the key for both the running key cipher (not in rules anymore) and the vigenere (they didn't give us the key for some reason, but it was SCIENCE so very guessable). However, we ran out of time on both, not being able to completely decrypt everything (the quotes were like very long. The Vigenere one was a decent paragraph). A similar thing happened to me at an early invite, where we had 70% of the letters in an aristocrat and we figured out the shift in a caesar cipher (very bad invite cuz the caesar cipher was disguised as a "mystery cipher" even though that was taken off the rules last year), but we ran out of time on both again.

Does anyone have any tips on how to prevent this kind of thing from happening? Divide and conquer seems like an optimal strategy, but it doesn't help if this kind of thing keeps happening.

[will0416]

Hi, kind of similar to the questions previously asked, but what is the best way to manage time?

I ask this because of the following scenario that happened at state last year: We break up the test, so everyone is working on their own cipher. When there are 5 minutes left, we check progress. We figured out the key for both the running key cipher (not in rules anymore) and the vigenere (they didn't give us the key for some reason, but it was SCIENCE so very guessable). However, we ran out of time on both, not being able to completely decrypt everything (the quotes were like very long. The Vigenere one was a decent paragraph). A similar thing happened to me at an early invite, where we had 70% of the letters in an aristocrat and we figured out the shift in a caesar cipher (very bad invite cuz the caesar cipher was disguised as a "mystery cipher" even though that was taken off the rules last year), but we ran out of time on both again.

Does anyone have any tips on how to prevent this kind of thing from happening? Divide and conquer seems like an optimal strategy, but it doesn't help if this kind of thing keeps happening.

The only thing that will really help out with unfinished ciphers like that will be making individual improvements on being more efficient on “messier” ciphers like Vigenere (i.e. doing more mental math if you’re the kind of person who likes to write everything out). There isn’t really a groundbreaking strategy to follow; it really depends on your style. If you feel like you can manage your time well, then it could be beneficial to start with the hard ciphers and end with easier aristocrats, but there’s also the option of going easy to hard if you need something to keep you on track to finish.

I’d just focus on making improvements on Vigenere and on your timed question, since it’ll give you more time to work with if you finish faster. It wouldn’t hurt to experiment with the order you complete the ciphers, but it won’t end up making an astronomical difference.

[snowzob]

I haven't bought a calculator for this season yet, I've been using the calculator app on my phone. On the phone inputting 80 - 8 * 9 gives me 8 which is what I want. But most four function calculators would output 648 because it does (80 - 8) * 9. Does anyone know if there is a four function calculator out there that would do what the calculator on the iphone does. or does anyone know any 5 function calculators whose 5th function is mod?

[pepperonipi]

I haven't bought a calculator for this season yet, I've been using the calculator app on my phone. On the phone inputting 80 - 8 * 9 gives me 8 which is what I want. But most four function calculators would output 648 because it does (80 - 8) * 9. Does anyone know if there is a four function calculator out there that would do what the calculator on the iphone does. or does anyone know any 5 function calculators whose 5th function is mod?

80 mod 9 on a four-function calculator:

1. 80/9 = 8.8888888...
2. 8.8888888... - 8 (the whole number) = 0.8888888...
3. .8888888 * 9 (the modulus) = 8 (or 7.9999/8.0001)

Really, after some practice, this didn't take much time.

[Name]

I haven't bought a calculator for this season yet, I've been using the calculator app on my phone. On the phone inputting 80 - 8 * 9 gives me 8 which is what I want. But most four function calculators would output 648 because it does (80 - 8) * 9. Does anyone know if there is a four function calculator out there that would do what the calculator on the iphone does. or does anyone know any 5 function calculators whose 5th function is mod?

80 mod 9 on a four-function calculator:

1. 80/9 = 8.8888888...
2. 8.8888888... - 8 (the whole number) = 0.8888888...
3. .8888888 * 9 (the modulus) = 8 (or 7.9999/8.0001)

Really, after some practice, this didn't take much time.

Do it repeatedly and it can really add up.

[jimmy-bond]

When calculating a private key in the RSA cipher using the extended Euclidean Algorithm, is there any reason to solve for s throughout your calculations? The answer keys I've been looking at keep telling me to solve for all 3 variables but it looks to me that s is a waste of time.