Table of Contents

HackTheBox - Challenge - Crypto - Weak RSA

The HTB “Weak RSA” Crypto is an easy challenge based on the RSA cipher.

Provided Files:

You are provided with the following files:

  • flag.enc
  • key.pub

Walk-through:

At first glance, you’d think you can decrypt the flag with the public key.
For that, we might use the OpenSSL package to decrypt the flag. This time it’s a bit different and you’ll find that the OpenSSL package won’t work for this challenge.

We’ll use an automated RSA attack tool. A common python script is the RsaCtfTool

python3 RsaCtfTool.py --publickey ./key.pub --uncipherfile ./flag.enc 

Simply put, this tool finds the flag easily for you in an automated fashion.

Flag Example:

HTB{XXXXXX_XXXXXXX_XXXXXX}