Examples associated with boot authentication are described. One example includes initiating a power on self-test (POST) phase of a boot of a system. Prior to initiating a driver execution environment phase of the POST phase, a network stack may be loaded for a network port. An encrypted key may be retrieved from a trusted component of the system. Boot of the system may be permitted to proceed upon establishing a connection with an authentication server, and authenticating the system to the authentication server based on the encrypted key.