John the Ripper or John is a great password/hash cracking. Say you find/obtain a private key for a user and wish to use it to leverage SSH, you can take the private key and attempt to crack it. First grab the id_rsa private key and copy the contents into a text document (make sure to leave a space at the end otherwise it may cause issues). Convert the private key to a readable hash for John: `ssh2john {private_key.txt} > hash.txt` `John hash.txt --wordlist=/usr/share/wordlists/rockyou.txt` To view the cracked password(s) use the following command: `John --show hash.txt`