Cracking SSH Private key passphrase

Using John the Ripper!

Upgrade your ethical hacking skills through this A to Z Cyber Security Training Bundle (Limited Time Offer!)

Step 1

Copy the SSH key you want to crack.

cp /.ssh/id_rsa id_rsa

Step 2

To brute-force using john, we have to convert it into a suitable format. For this, we can use ssh2john.py. This comes pre-installed in Kali Linux. You can find it using locate command and copy it to your current working directory.

updatedb #updatedb creates or updates a database used by locate(1)
locate ssh2john.py
cp $(locate ssh2john.py).

Step 3

Next, you have to create a hash file from the id_rsa file to use it with john.

python ssh2john.py id_rsa > id_rsa.hash

Step 4

To conduct the brute force, you need a wordlist. You can try the rockyou wordlist pre-installed in Kali Linux.

locate rockyou.txt.gz
cp $(locate rockyou.txt.gz) .

Unzip the file,

gunzip rockyou.txt.gz

Step 5

At last, we can use john to crack the hash using rockyou.txt and retrieve the passphrase.

john id_rsa.hash -wordlist=rockyou.txt

Good Luck cracking it!

Follow my socials for more cybersecurity content. 📝

Sajeth Jonathan - Colombo District, Western Province, Sri Lanka | Professional Profile | LinkedIn

JavaScript is not available.