PicoCTF Writeup – Mind your Ps and Qs
# Information:
CTF Name: PicoCTF
CTF Challenge: Mind your Ps and Qs
Challenge Category: Cryptography
Challenge Points: 20
picoCTF 2021.
# Used Tools:
- Linux
- RSA Decoder
# Challenge Description:
In RSA, a small e value can be problematic, but what about N? Can you decrypt this? values
Hints:
# Writeup:
Hello, and welcome to another picoCTF challenge write-up. First, we downloaded the file called “values” (that you can obtain under “Challegge Description”).
Step 1:
We begin by opening the “values” file with the command cat that you can see in Image 1.
By doing this, we were able to see the values e, n, and c.
After seeing the values, we researched the meanings of the values.
The values n and e are public keys, and the c value is a ciphertext.
After knowing this, we searched for an RSA decoder.
You can obtain the RSA decoder here.
Step 2:
We incerted the information in the RSA decoder (as you can see in the Image 2).
we got the flag.
The flag is:
Bibliography:
https://en.wikipedia.org/wiki/RSA_(cryptosystem)
Thank you very much for reading!
Cheers,
SoBatista
