To generate new RSA SSH key type the following command in the Raspberry PI terminal:
ssh-keygen -t rsa
confirms the name of the file with ENTER and enter a passphrase (recommended).
For Ed25519 keys type (may not work properly):
ssh-keygen -t ed25519
For ECDSA keys type:
ssh-keygen -t ecdsa
If you don’t use any passphrase you need to edit the file /etc/ssh/sshd_config with 'PermitEmptyPasswords yes'.