A network controller configured to provide network access to client devices, receives a network access request from a client device. The network access request includes a media access control (MAC) address of the client device and information about a first private key. The network controller sends to a server an authentication request, which includes the MAC address of the client device. The network controller receives an authentication response from the server, which includes a second private key. The network controller determines whether the first private key is the same as the second private key. In response to determining that the first private key is different from the second private key, network access is denied to the client device, and in response to determining that the first private key is the same as the second private key, network access is granted to the client device.