The present invention relates to a
system and method for digitally authenticating users both
online and offline. In one embodiment, a hardware token assigned by a trusted token provider to the user is employed to ensure the identity of the user. In the online
authentication, the token is adapted for generating an exposed key EK and a hidden key HK based on a
noise code NC and a time code TC of the token, a space code SC of a service
server, and an owner code OC of the user. A
login session is initialized by entering a
user identifier at the service
server and the generated EK from a computing device. The service
server computes an
expose key CEK and a hidden key CHK based one an
authentication license generated by the token provider. The service server authenticates the user if the CEK is same as the EK, and sends a response message encrypted the CHK to the computing device. Then, the user provides the HK to the computing device to decrypt the encrypted response message so as to access his / her account. In the offline
authentication, the token is adapted for generating a
license exposed key LEK used to render the encrypted
digital content on an offline compliant device. The compliant device authenticates the user if a
license exposed key computed by the compliant device based on a content license of which the user bought is same as LEK, so as to render the protected
digital content after authentication.