blecc.md

blecc (146 solves/119 points)

Description:

Blecc! What are all these numbers? This doesn't look like RSA... output.txt

Solution:

Let's open up the file and see what we have

p = 17459102747413984477
a = 2
b = 3
G = (15579091807671783999, 4313814846862507155)
Q = (8859996588597792495, 2628834476186361781)
d = ???
Can you help me find `d`?
Decode it as a string and wrap in flag format.

For a while, my team was stumped until we figured out it was ECC encryption. From there, we knew that we had to find the private key d somehow. Using sagemath, here is the solve script using the discrete_log function.

p = 17459102747413984477
a = 2
b = 3
E = EllipticCurve(GF(p), [a,b])
P = E(15579091807671783999, 4313814846862507155)  # P in this case was represented by G in output.txt
Q = E(8859996588597792495, 2628834476186361781)
print('d =', hex(discrete_log(Q,P,P.order(),operation='+'))[2:])

Our output: d = 6d316e315f336363 From there we just decrypt the hex to ASCII to get our flag!

Flag:

flag{m1n1_3cc}