Codebusters C

Post Reply
User avatar
Name
Member
Member
Posts: 434
Joined: January 21st, 2018, 4:41 pm
Division: C
State: NY
Pronouns: He/Him/His
Has thanked: 49 times
Been thanked: 46 times

Re: Codebusters C

Post by Name »

Avalanche wrote:I was reading the rules to make sure I wasn't wasting to much time reading about the state/nats ciphers, and noticed that for the hill cipher it states, "Mathematical Cryptanalysis of the Hill Cipher - either producing a decryption matrix given a 2x2 encryption matrix or computing a decryption matrix given 4 plaintext-ciphertext letter pairs." What does this rule even mean.

Thanks
They can test a hill cipher so that when given a hill cipher matrix they can ask find the inverse key of the matrix or given 4 plaintext crib find the key

So like they can asks find the inverse of
|1 2|
|3 7|
or something like that (usually in order to then decode something)

Or they can ask something like
if the plain text abcd corresponds to the ciphertext efgh find the key used to encrypt/decrypt it
South Woods MS, Syosset HS '21
BirdSO TD/ES
Past Events: Microbe, Invasive, Matsci, Fermi, Astro, Code, Fossils
1st place MIT Codebusters 2019-2020
1st place NYS Fermi Questions (2019), Astronomy and Codebusters (2021)
Science Olympiad Founder's Scholarship winner
Avalanche
Member
Member
Posts: 34
Joined: September 19th, 2017, 6:14 pm
Has thanked: 1 time
Been thanked: 1 time

Re: Codebusters C

Post by Avalanche »

Name wrote:
Avalanche wrote:I was reading the rules to make sure I wasn't wasting to much time reading about the state/nats ciphers, and noticed that for the hill cipher it states, "Mathematical Cryptanalysis of the Hill Cipher - either producing a decryption matrix given a 2x2 encryption matrix or computing a decryption matrix given 4 plaintext-ciphertext letter pairs." What does this rule even mean.

Thanks
They can test a hill cipher so that when given a hill cipher matrix they can ask find the inverse key of the matrix or given 4 plaintext crib find the key

So like they can asks find the inverse of
|1 2|
|3 7|
or something like that (usually in order to then decode something)

Or they can ask something like
if the plain text abcd corresponds to the ciphertext efgh find the key used to encrypt/decrypt it
Thanks, for the help.
Boyceville/Gopher/Regionals/State
Herpetology: 3/2/-/2
Solar System: 12/2/-/5
Road Scholar: -/-/2/1
Experimental Design: -/1/-/-
User avatar
TheChiScientist
Member
Member
Posts: 732
Joined: March 11th, 2018, 11:25 am
Division: Grad
State: IL
Pronouns: He/Him/His
Has thanked: 6 times
Been thanked: 44 times

Re: Codebusters C

Post by TheChiScientist »

I was wondering if anyone has any good sources for practice with Spanish Xenocrypts? I can't seem to find anything on the internet...
A Science Olympian from 2015 - 2019 CLCSO Alumni
Medal Count:30
IL PPP/Mission Assistant State Supervisor.
CLC Div. B Tournament Director.
President of The Builder Cult.
"A true Science Olympian embraces a life without Science Olympiad by becoming a part of Science Olympiad itself"- Me
Anomaly
Exalted Member
Exalted Member
Posts: 642
Joined: February 17th, 2017, 10:46 am
Division: C
State: PA
Pronouns: She/Her/Hers
Has thanked: 4 times
Been thanked: 10 times

Re: Codebusters C

Post by Anomaly »

TheChiScientist wrote:I was wondering if anyone has any good sources for practice with Spanish Xenocrypts? I can't seem to find anything on the internet...
Just ask someone to create one for you. It only takes a minute to make.
Orefield MS SO 2015-2018, Parkland HS SO 2019-2020
Medal/Ribbon Count
Invitational: 25
Regional: 16
State: 7
y o i n k s
Events: Anatomy and Physiology, Codebusters, Designer Genes, Protein Modeling
don't look at this its fake news now
User avatar
Name
Member
Member
Posts: 434
Joined: January 21st, 2018, 4:41 pm
Division: C
State: NY
Pronouns: He/Him/His
Has thanked: 49 times
Been thanked: 46 times

Re: Codebusters C

Post by Name »

I haven't ever seen questions related to RSA on any invite test so far, and it seems nearly impossible to encode/decode with only a 5 function calculator. Is the only thing that can be realistically tested is to find the decryption key given the encryption key?
South Woods MS, Syosset HS '21
BirdSO TD/ES
Past Events: Microbe, Invasive, Matsci, Fermi, Astro, Code, Fossils
1st place MIT Codebusters 2019-2020
1st place NYS Fermi Questions (2019), Astronomy and Codebusters (2021)
Science Olympiad Founder's Scholarship winner
User avatar
dragonfruit35
Exalted Member
Exalted Member
Posts: 296
Joined: February 28th, 2015, 7:49 am
Division: Grad
State: VA
Pronouns: She/Her/Hers
Has thanked: 7 times
Been thanked: 1 time

Re: Codebusters C

Post by dragonfruit35 »

Name wrote:I haven't ever seen questions related to RSA on any invite test so far
That’s because RSA isn’t on the list of invy/regs ciphers in the rules- it’s listed in the section to be used at state competitions and Nats :)
tjhsst '20
virginia tech '24
2x codebusters national medalist

"it's not a pen, it's a principle!" - annie edison
UTF-8 U+6211 U+662F
Exalted Member
Exalted Member
Posts: 1597
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 6 times
Been thanked: 15 times

Re: Codebusters C

Post by UTF-8 U+6211 U+662F »

Name wrote:I haven't ever seen questions related to RSA on any invite test so far, and it seems nearly impossible to encode/decode with only a 5 function calculator. Is the only thing that can be realistically tested is to find the decryption key given the encryption key?
Wait, why is it nearly impossible to encode/decode with a 5 function calculator

(Forgive me, I don't really do this event)
User avatar
Riptide
Exalted Member
Exalted Member
Posts: 202
Joined: December 4th, 2017, 7:09 pm
Division: Grad
State: TX
Has thanked: 0
Been thanked: 8 times
Contact:

Re: Codebusters C

Post by Riptide »

UTF-8 U+6211 U+662F wrote:
Name wrote:I haven't ever seen questions related to RSA on any invite test so far, and it seems nearly impossible to encode/decode with only a 5 function calculator. Is the only thing that can be realistically tested is to find the decryption key given the encryption key?
Wait, why is it nearly impossible to encode/decode with a 5 function calculator

(Forgive me, I don't really do this event)
RSA deals with encrypting/decrypting using exponents, which can get very large. Smaller exponents are doable but I don’t know if 4/5 function calculators can even handle going to such high numbers.
UC Berkeley
Seven Lakes High School '19
UTF-8 U+6211 U+662F
Exalted Member
Exalted Member
Posts: 1597
Joined: January 18th, 2015, 7:42 am
Division: C
State: PA
Has thanked: 6 times
Been thanked: 15 times

Re: Codebusters C

Post by UTF-8 U+6211 U+662F »

Riptide wrote:
UTF-8 U+6211 U+662F wrote:
Name wrote:I haven't ever seen questions related to RSA on any invite test so far, and it seems nearly impossible to encode/decode with only a 5 function calculator. Is the only thing that can be realistically tested is to find the decryption key given the encryption key?
Wait, why is it nearly impossible to encode/decode with a 5 function calculator

(Forgive me, I don't really do this event)
RSA deals with encrypting/decrypting using exponents, which can get very large. Smaller exponents are doable but I don’t know if 4/5 function calculators can even handle going to such high numbers.
Presumably they won't use large exponents on the test (otherwise, the code would be very hard to decipher!). However, since RSA uses modular arithmetic, you can use various tricks to get smaller numbers after exponentiation.
User avatar
TheChiScientist
Member
Member
Posts: 732
Joined: March 11th, 2018, 11:25 am
Division: Grad
State: IL
Pronouns: He/Him/His
Has thanked: 6 times
Been thanked: 44 times

Re: Codebusters C

Post by TheChiScientist »

Anyone here wants access to an xenocrypt test urgently? I plan to complete a SciOly Codebusters test of pure xenocrypts seeing how difficult they are to find but I don't want to release it without a large number of ciphers if there isn't a large demand.
A Science Olympian from 2015 - 2019 CLCSO Alumni
Medal Count:30
IL PPP/Mission Assistant State Supervisor.
CLC Div. B Tournament Director.
President of The Builder Cult.
"A true Science Olympian embraces a life without Science Olympiad by becoming a part of Science Olympiad itself"- Me
Post Reply

Return to “2019 Lab Events”

Who is online

Users browsing this forum: No registered users and 1 guest