Patent ID: 8724810

Claim:
A method for auth enticating onboard units, which can conduct dedicated short-range communication (DSRC) communications with beacons of a road toll system, wherein upon a communication from an onboard unit the derivation code is transmitted to the beacon to enable the beacon to emulate the individual key for encrypting or decrypting the communication with the onboard unit or for accessing data stored in the onboard unit, the method comprising: storing a pool of pairs of individual keys and associated derivation codes, in the onboard unit, wherein the beacons have a system-wide key and the onboard units only have individual keys, which are respectively formed from the system-wide key on the basis of a derivation code specific to each onboard unit; in the case of consecutive communications, selecting by the onboard unit a different pair of individual key and associated derivation code from the stored pool and using said selected pair for a respective communication; for authentication, causing the onboard unit by an interrogation device to conduct at least a portion of a radio communication, in which the onboard unit transmits to the interrogation device the selected associated derivation code; receiving the selected associated derivation code in the interrogation device and comparing it with the derivation codes of the pool; and authenticating the onboard unit when identity is established according to said comparing.