US Patent 9608981 Strong user authentication for accessing protected network

Systems and methods for strong user authentication for accessing protected networks. An example method may include: transmitting, by a processing device, an authentication request to an authentication server; receiving an access granting token from the authentication server; transmitting, to a nonce server, a nonce request using the access granting token; receiving a cryptographic nonce from the nonce server; and transmitting, to a virtual private network (VPN) server, a VPN connection request using the cryptographic nonce.