RSA Noob
60 points Medium

These numbers were scratched out on a prison wall. Can you help me decode them? https://mega.nz/#!al8iDSYB!s5olEDK5zZmYdx1LZU8s4CmYqnynvU_aOUvdQojJPJQ

Flag
Rating 4.43
5
4
3
2
1

Discussion

very cool little challenge. if you see the comments you'll see a bunch of people with differnet solutions they came up with. if you dont know how to program stuff and is lazy so you don't wanna download python3 to solve this, its easy. e=1 means that the private key, d, is also 1, if that happens, turn to the equation c = m^e mod n. e=1, so c = m mod n. ignore mod n for now, you'll see, it says that the OTHER private key, m, is actually equal to c. so to get the flag, you'll need to read the descriptions of RSA solvers and learn how it encrypts and decrypts stuff to and from RSA. you should only be using two translators and no more than that. (RSA solvers wont help so good luck)

1
Protected
0

Hint: use RsaCtfTool from github

1

How Euler's Theorem is used?

0

Convert the second number to hex and then to ascii

0

use python, not decoder, note the discussion here https://blog.noxtal.com/writeups/2020/05/28/ctflearn120/

0
Protected
1

NICE!!!

0

c = m^e mod n

Here we have c, e and n.. we need to calculate m. Since e = 1 its very easy to solve. Final value has to be converted from declimal to hexa to text

3