## Codebusters C

waterlubber
Member
Posts: 2
Joined: February 26th, 2018, 6:41 pm

### Re: Codebusters C

Anyone know about "ideal" calculators? Basically, the most digits (and with a memory, hopefully) that you can cram into a four-function. RSA is...calculationally demanding, to say the least.

UTF-8 U+6211 U+662F
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Posts: 1518
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA

### Re: Codebusters C

Anyone know about "ideal" calculators? Basically, the most digits (and with a memory, hopefully) that you can cram into a four-function. RSA is...calculationally demanding, to say the least.
I don't do this event but what part of the RSA are you using your calculator most for? It seems like given small primes, it shouldn't be that bad

jimmy-bond
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State: HI
Location: On Earth, I think

### Re: Codebusters C

On a practice test, I had the question "Encode DREW BREES using the keyword VEAR." It displayed VEAR as a 2x2 matrix, so this is clearly a Hill cipher problem. I tried encrypting it as I would a normal Hill cipher but got a different answer than the answer key. I'm pretty sure I did it wrong, so can someone explain to me how to do this problem and the solution you get? Thanks.
If life gives you melons, you're dyslexic.

Why can't dinosaurs ski? Because they're dead.

Season's over, I can sleep now.
Code Busters(16), DD(40), FQ(39), Forensics(36), WQ(27)
CriB(26), DP (11), FF(1), MM(14), P&P(6)
CriB(36), DD(35), FF(2), MM(20)

Anonymous15
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Joined: January 14th, 2019, 7:55 pm

### Re: Codebusters C

dragonfruit35
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Posts: 279
Joined: February 28th, 2015, 7:49 am
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State: VA
Location: TJHSST

### Re: Codebusters C

On a practice test, I had the question "Encode DREW BREES using the keyword VEAR." It displayed VEAR as a 2x2 matrix, so this is clearly a Hill cipher problem. I tried encrypting it as I would a normal Hill cipher but got a different answer than the answer key. I'm pretty sure I did it wrong, so can someone explain to me how to do this problem and the solution you get? Thanks.
Which way did you write the DREW BREES matrix? With the letters readable horizontally or vertically?
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jimmy-bond
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Posts: 314
Joined: January 8th, 2018, 11:25 pm
Division: C
State: HI
Location: On Earth, I think

### Re: Codebusters C

Which way did you write the DREW BREES matrix? With the letters readable horizontally or vertically?
Idk how to put a matrix but I did

D R
E W
B R
E E
S
If life gives you melons, you're dyslexic.

Why can't dinosaurs ski? Because they're dead.

Season's over, I can sleep now.
Code Busters(16), DD(40), FQ(39), Forensics(36), WQ(27)
CriB(26), DP (11), FF(1), MM(14), P&P(6)
CriB(36), DD(35), FF(2), MM(20)

Longivitis
Member
Posts: 28
Joined: February 17th, 2018, 7:19 am
State: TX

### Re: Codebusters C

Which way did you write the DREW BREES matrix? With the letters readable horizontally or vertically?
Idk how to put a matrix but I did

D R
E W
B R
E E
S
It's supposed to be
D
R
E
W
B
R
E
E
S
(Z)

and then multiply by the 2x2 matrix keyword
University of Texas at Austin '23
Cypress Lakes High School '19

Chemistry Lab, Codebusters, Game On, Science Word, Towers, We've Got Your Number

UTF-8 U+6211 U+662F
Exalted Member
Posts: 1518
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA

### Re: Codebusters C

Which way did you write the DREW BREES matrix? With the letters readable horizontally or vertically?
Idk how to put a matrix but I did

D R
E W
B R
E E
S
It's supposed to be
D
R
E
W
B
R
E
E
S
(Z)

and then multiply by the 2x2 matrix keyword
You can't multiply those two matrices. They don't line up. It's supposed to be
the VEAR matrix multiplied by $\begin{vmatrix}D\\R\end{vmatrix}$
and then the VEAR matrix multiplied by $\begin{vmatrix}E\\W\end{vmatrix}$
etc., etc., I believe.

Although annoyingly, it's not evenly split into chunks of 2 so you'd have to insert an extra letter at the end.

Longivitis
Member
Posts: 28
Joined: February 17th, 2018, 7:19 am
State: TX

### Re: Codebusters C

Idk how to put a matrix but I did

D R
E W
B R
E E
S
It's supposed to be
D
R
E
W
B
R
E
E
S
(Z)

and then multiply by the 2x2 matrix keyword
You can't multiply those two matrices. They don't line up. It's supposed to be
the VEAR matrix multiplied by $\begin{vmatrix}D\\R\end{vmatrix}$
and then the VEAR matrix multiplied by $\begin{vmatrix}E\\W\end{vmatrix}$
etc., etc., I believe.

Although annoyingly, it's not evenly split into chunks of 2 so you'd have to insert an extra letter at the end.
Yeah, that's what I meant guess I really wasn't clear enough.
University of Texas at Austin '23
Cypress Lakes High School '19

Chemistry Lab, Codebusters, Game On, Science Word, Towers, We've Got Your Number

dragonfruit35
Exalted Member
Posts: 279
Joined: February 28th, 2015, 7:49 am
Division: C
State: VA
Location: TJHSST

### Re: Codebusters C

It's supposed to be
D
R
E
W
B
R
E
E
S
(Z)

and then multiply by the 2x2 matrix keyword
You can't multiply those two matrices. They don't line up. It's supposed to be
the VEAR matrix multiplied by $\begin{vmatrix}D\\R\end{vmatrix}$
and then the VEAR matrix multiplied by $\begin{vmatrix}E\\W\end{vmatrix}$
etc., etc., I believe.

Although annoyingly, it's not evenly split into chunks of 2 so you'd have to insert an extra letter at the end.
Yeah, that's what I meant guess I really wasn't clear enough.
Yeah, UTF is right, it should be $\begin{vmatrix}D\\R\end{vmatrix}$ $\begin{vmatrix}E\\W\end{vmatrix}$ $\begin{vmatrix}B\\R\end{vmatrix}$ $\begin{vmatrix}E\\E\end{vmatrix}$ $\begin{vmatrix}S\\Z\end{vmatrix}$ multiplied by the encryption key, in whichever orientation they gave it to you, to be clear.
(VT/FFX/Reg/States/Nats)
MV 1/1/5/-/- Mission 3/4/4/-/- Herp 7/2/4/-/-
WiFi -/-/-/4/13  Indoor Bottle Rocket -/-/-/1/- Code -/-/-/-/1
(Duke/Reg/Cornell/States/Nats)
MV 2/3/7/3/10 Mission 3/7/- Sounds 4/2/- Code 3/1/1/1/5 Herp -/-/11/1/26
[/color]
Goooooooo Colonials!!!