Permissions on private key in .ssh folder
.ssh directory: 700 (drwx——)
public key (.pub file): 644 (-rw-r–r–)
private key (id_rsa): 600 (-rw——-)
chmod 600 ~/.ssh/id_rsa_*
chmod 600 ~/.ssh/*/id_rsa
lastly your home directory should not be writable by the group or others (at most 755 (drwxr-xr-x)).
Source: https://superuser.com/questions/215504/permissions-on-private-key-in-ssh-folder
Kill unresponsive ssh session
Enter -> ~ -> .