This one should be an easy one for anyone out there:
GUVF VF N FGNAQNEQ NAQ PBZZBA EBG GUVEGRRA PNRFNE PVCURE. UBJ DHVPXYL QVQ LBH FBYIR VG JVGUBHG HFVAT BAYVAR ERFBHEPRF?
Re: Codebusters C
Posted: September 13th, 2018, 8:01 am
by trdd
Per (f.vi.) at least one of them has to be in Spanish for State and Nationals. So here's an easy standard one in Spanish. It is the first verse of a ridiculous hyperbolic poem: Try to solve it by hand without computers and post how fast you did.
FV QVBF HA QVN PRTNEN GBQN SHRAGR QR YHM, RY HAVIREFB FR NYHZOENEVN PBA RFBF BWBF DHR GVRARF GH.
Re: Codebusters C
Posted: September 13th, 2018, 5:11 pm
by Birdmusic
trdd wrote:This one should be an easy one for anyone out there:
GUVF VF N FGNAQNEQ NAQ PBZZBA EBG GUVEGRRA PNRFNE PVCURE. UBJ DHVPXYL QVQ LBH FBYIR VG JVGUBHG HFVAT BAYVAR ERFBHEPRF?
This is a standard and common rot thirteen shift cipher. How quickly did you solve it without using online resources?
Re: Codebusters C
Posted: September 15th, 2018, 5:43 pm
by Birdmusic
Name wrote:Oh.
Invert the following encryption matrix
| 5 7|
| 2 1|
ESRKPWPDJZ was encoded using the previous matrix. Using the inverted matrix decode the cipher text
Work:
Inverse is
|1 -7| *23 (the multiplicative inverse mod 26 of the determinant of the matrix, -9 or17)
|-2 5|
[b]|23 21|
|6 11| (mod 26)[/b]
The code made into numbers is 4,18, 17, 10, 15, 22, 15, 3, 9, 25
After multiplying:
[b]CODEBUSTERS[/b]
Re: Codebusters C
Posted: September 15th, 2018, 5:46 pm
by Name
Birdmusic wrote:
Name wrote:Oh.
Invert the following encryption matrix
| 5 7|
| 2 1|
ESRKPWPDJZ was encoded using the previous matrix. Using the inverted matrix decode the cipher text
Work:
Inverse is
|1 -7| *23 (the multiplicative inverse mod 26 of the determinant of the matrix, -9 or17)
|-2 5|
[b]|23 21|
|6 11| (mod 26)[/b]
The code made into numbers is 4,18, 17, 10, 15, 22, 15, 3, 9, 25
After multiplying:
[b]CODEBUSTERS[/b]
yup. your turn
Re: Codebusters C
Posted: September 16th, 2018, 2:31 pm
by Birdmusic
Encrypt the message “Affine cipher” with an affine cipher where a=7 and b=12.
Re: Codebusters C
Posted: September 16th, 2018, 3:12 pm
by Name
Birdmusic wrote:Encrypt the message “Affine cipher” with an affine cipher where a=7 and b=12.
MVVQZO AQNJOB
(I think this is how RSA works)
The public key is c = m^5 mod 91
Find the private key
Re: Codebusters C
Posted: September 16th, 2018, 4:51 pm
by UTF-8 U+6211 U+662F
Name wrote:
Birdmusic wrote:Encrypt the message “Affine cipher” with an affine cipher where a=7 and b=12.
MVVQZO AQNJOB
(I think this is how RSA works)
The public key is c = m^5 mod 91
Find the private key
I don't do this event, but yay codes!
And the result which I'm pretty sure is right:
And that's why you should always choose large primes.
Decode LCHSYZOJHEAOJODYCNEWEHDIQBGD, which was encrypted using the Vigenère cipher with a key of TOWEL.
Re: Codebusters C
Posted: September 16th, 2018, 5:05 pm
by Name
UTF-8 U+6211 U+662F wrote:
Name wrote:
(I think this is how RSA works)
The public key is c = m^5 mod 91
Find the private key
I don't do this event, but yay codes!
And the result which I'm pretty sure is right:
And that's why you should always choose large primes.
Decode LCHSYZOJHEAOJODYCNEWEHDIQBGD, which was encrypted using the Vigenère cipher with a key of TOWEL.
Im pretty sure its
m^5 mod 91
Primes are 7 annd 13
Subtract one from each so 6 and 12
6*12=72
5X=1mod72
X=29
=c^29 mod 91
I might be wrong im not familiar with RSA
Re: Codebusters C
Posted: September 16th, 2018, 5:58 pm
by UTF-8 U+6211 U+662F
Name wrote:
UTF-8 U+6211 U+662F wrote:
Name wrote:
(I think this is how RSA works)
The public key is c = m^5 mod 91
Find the private key
I don't do this event, but yay codes!
And the result which I'm pretty sure is right:
And that's why you should always choose large primes.
Decode LCHSYZOJHEAOJODYCNEWEHDIQBGD, which was encrypted using the Vigenère cipher with a key of TOWEL.
Im pretty sure its
m^5 mod 91
Primes are 7 annd 13
Subtract one from each so 6 and 12
6*12=72
5X=1mod72
X=29
=c^29 mod 91
I might be wrong im not familiar with RSA
The expressions are equivalent (to the best of my mathematical knowledge)
Edit: No they're not, sorry.
I believe what you calculated is the expression for the public key. For the values I tested, , which means you're effectively multiplying the expression for the public key by 1. Why , I have no idea.