what’s the field before ssh-rsa in know_hosts on Raspbian GNU/Linux 9 (stretch)

ssh-gen by default creates a public key like

ssh-rsa AAAAB3NzaC1yc2E…6OEBTVwLRP1Ocyr user@DESKTOP-8BL3U5O

The Raspbian 9 has a different format

|1|dMpV8+ILjAAD11mhp57Q7hVk/4A=|pvCuzPyguQCwV9cN908uBz6CZLE= ssh-rsa AAAAB3NzaC1yc2E…6OEBTVwLRP1Ocyr

What is the field before ssh-rsa. How to generate it so id_rsa.pub can be inserted into know_hosts?