Patent ID: 9548984
Date: 2017-01-17
CPC Classifications: G05B,H04L,H04W,Y02P

Claim:
1. A method for authorizing a user at a field device by a portable communications device, the method comprising: acquiring a first information by the portable communications device for identifying the field device; sending to a system the first information and sending a second information including information which identifies (i) the portable communications device and (ii) a role of the user thereof, by the portable communications device; determining, by the system, a first piece of access information on the basis of the first information and the second information, and sending by the system the first piece of access information to the portable communications device; transmitting by the portable communications device the second information including the information which identifies (i) the portable communications device and (ii) the role of the user thereof, and the first piece of access information to the field device; determining, by the field device, a second piece of access information on the basis of the second information including the information which identifies (i) the portable communications device and (ii) the role of the user thereof, and comparing the first piece of access information with the second piece of access information; and allowing access to the field device upon determining that the first piece of access information and the second piece of access information match, wherein: the system and the field device are provided with a shared secret; the portable communications device sends a date in addition to the first information and the second information to the system; the system uses the shared secret to calculate from the first information, the second information and the date, a first one-time password as the first piece of access information; and the field device uses the shared secret to calculate, from the second information and the date and from the first information known to the field device, a second one-time password as the second piece of access information.