• download putty (installer + associating ppk files makes your life easier but is not a must)
• launch puttygen [Win key → type: puttygen → enter]
  • type the name of the key
  • type the password (if you intend to use it from your phone - maybe less than one bazillion characters)
  • set: ssh-2-rsa 4096 bit
  • press generate
  • save the public key in OpenSSH into a textfile e.g. mykey_OpenSSH.pub (conversions → export OpenSSH key)
  • save the public key in ssh.com format e.g. mykey_ssh.com.pub (conversions → export ssh.com key)

This assumes you completed key_request.

• open putty
  • enter hostname portal.portal
  • go to connection → data
    • enter Auto-login username: open
  • go to connection → ssh → auth
    • browse for your private key file for authentication (see generate a 4096 bit ssh-2-rsa key)
  • go back to session (first screen)
    • Saved Sessions: open shack
    • press save

• select „open shack“ (see setup opening the shack door)
  • click load
  • click open
  • beep ba beep bup
  • shack is now open and you are the keyholder (see Hausrecht)

• launch puttygen [Win key → type: puttygen → enter]
  • conversions → import key
  • import your private key
  • save private key (in putty ppk format)