NKey is an excellent replacement for token authentication because a connecting client will have to prove it controls the private key for the authorized public key.
Sfor Seed. The second letter,
Ustands for User. Seeds are private keys; you should treat them as secrets and guard them with care.
Ufor User and is a public key which can be safely shared.
nkeyproperty to the public key of the user you want to authenticate:
nkeyproperty (user/password/token properties are not needed). Add
permissionsections as required.