Level 13: Key Not Password

You hit a wall here: there is no password for the next level. Instead, you're given a private SSH key.

If you've never dealt with keys before, it can feel weird because the login process is different. You aren't providing a secret string to the server; you're providing a file that proves you are the authorized user.

The trick is the -i flag in SSH. It stands for "identity." By using it, you're telling the SSH client: "Don't ask for a password, use this specific key file to authenticate me."

ssh -i sshkey.private ghost13@localhost

Once you're in, the password for the next level is just sitting there in the flag.

Result: REDACTED

TL;DR: When there's no password, look for a private key and use ssh -i <keyfile> to authenticate.