Method for DSRC communication

The present invention relates to a DSRC communication method between roadside navigation devices (baken) and on-board toll system devices, the road navigation devices having the key for the entire system, and the on-board devices do not have a key for the whole system, but individual keys, of which each is created from a key for the entire system based on a specific code for each on-board device, with the output code being sent from the on-board unit to the road navigation device during communication to enable the on-board navigation device to recover an individual key for encrypting or decrypting communication with the on-board device and / or for access to data stored in the on-board unit.

[0002] From document EP 0 769 763 A2 a method of encryption is known for communication between roadside navigation devices and on-board devices which, at the beginning of communication, exchange the exit codes for this communication with a roadside navigation device. On-board equipment also has local key copies for the entire system.

[0003] DSRC (Dedicated Short Range Communication Toll Systems) are standardized, for example, in ISO 14906 and EN 15509; DSRC communication on the radio interface can be, for example, according to the standard

WAVE reasons

IEEE 1609.11. For security purposes, in such DSRC toll systems, keys for the entire system (Master Keys) are not stored in Onboard Units (OBU), but they receive only individual, derived from them

-3keywords (Derived Keys). Only these individual keys are transmitted or used by the DSRC radio interface.

[0004] The output code required here, in the standards ISO 14906 or EN 15509 referred to as the "Key Diversifier", is the individual for each device on board the code of the used rule for deriving a key (Derived Key) from the key for the entire system (Master Key). The key coding code (Key Diversifier) ​​is according to the prior art provided to the roadside navigation device by the on-board unit for every communication between the on-board unit and the roadside navigation device so that it can output the on-board key for the whole system in the on-fly mode. communication or access to the on-board device.

[0005] The present invention is based on the belief that this constellation is associated with data protection problem: Since the output code specific to the on-board device is first sent from the on-board unit via the radio interface at each DSRC radio communication, it would be possible, by eavesdropping. radio interface or a deliberate, dishonest reading of a passing on-board device, identify these on-board devices and thus track its path. Thus, a traffic profile of a specific on-board unit or user in the toll system could be created.

[0006] The invention solves the problem of data protection recognized for the first time in that an on-board device sends out changing exit codes in such a way that a roadside device communicates with successive roadside navigation devices.

During navigation with the on-board device, it sends at least one new pair of an individual key and the associated key of the pin, which the on-board device uses during the next communication. In this way, it is no longer possible to track the on-board unit for a long time or on several road sections of the navigation devices based on the output codes they send in the DSRC communications. According to the invention, the exit codes on the path of the on-board unit are constantly changing over several road sections of the navigation devices.

[0007] Preferably, the road navigation device sends said pair at the end of communication and particularly preferably also only at low current communication rate ("depending on the traffic volume"), so as not to interfere with the toll function by additional data protection functions.

[0008] According to a preferred further embodiment of the invention, a set of pairs of individual keys and associated lead codes is recorded in the on-board unit and the on-board unit selects a pair from this resource for communication with the road-based navigation device, and the on-board navigation device is used for this communication. as part of communication with the on-board device, it sends to it at least one new pair of an individual key and an associated lead key which the on-board device stores in its resource for subsequent selection. As a result, a high degree of data security can be achieved because the output code changes frequently and at the same time the additional load on road navigation devices and radio interfaces is reduced. Preferably, said pair in the device

- the land deck is selected randomly or at least pseudo-randomly from the resource.

[0009] The invention is particularly suitable for communication according to the standards ISO 14906 or EN 15509 regarding DSRC or according to compatible standards, wherein the lead code is Key Diversifier from these standards.

[0010] The invention is explained below in more detail on the basis of the exemplary embodiments illustrated in the accompanying drawings. On drawings

Figures 1 and 2 are block diagram and sequence diagram of a first embodiment of a method according to the invention; and

Figs. 3 and 4 are block diagram and sequence diagram of a second embodiment of the method according to the invention.

[0011] In Figs. 1 to 4, an exemplary Onboard Unit OBU and an exemplary Roadside Equipment RSE of a toll system with a plurality of on-board devices of the RSE navigational devices are shown.

OBU and

The OBU and Roadside Roadside Devices of the RSE navigational devices communicate with each other via the radio interface 1 with a short DSRC standard, in particular the range according to (Dedicated Short Range Communication), according to ISO 14906 or EN 15509 or according to standards based on them or compatible with them. Two different embodiments of the DSRC communication method according to the invention on the radio interface 1 are shown on one side in Figs. 1 and 2 and on the other hand in Figs. 3 and 4.

[0012] In both variants, roadside RSE navigational devices have one or more keys for the entire MK (Master Keys) system. For example, they have a connection to a (not shown) control panel that manages the key or MK keys for the entire system for roadside RSE navigational devices, or that separates them between roadside navigation devices.

[0013] For security reasons, the MK key for the entire system is not stored in OBU on-board devices, but they only contain DK (Derived Keys) keys derived from it. Individual DK keys can be used to encrypt communications on radio interface 1 (as "Encryption Keys") and / or as access rights ("Access Credential Keys") for access to data stored in an OBU on-board unit, as is known to one skilled in the art. .

The individual DK keys are output from the MK key for the entire system according to a given output rule, the "Key Diversifier" Div identifies the applied and device-specific output rule or is the parameter for this output rule, i.e.

DK = f (MK, Div).

[0015] Only when knowing the Div output code can an individual DK key be created from the MK key for the entire system.

[0016] According to a variant of the method of Figs. 1 and 2, the RSE roadside navigation device sends in its first step its service overview (Beacon Service Table, BST) to the OBU on-board device to be driven. The OBU on-board device then responds with its own service overview

-7 (Vehicle Service Table, VST), which also contains its current Div code (step 3). The RSE roadside navigation device can now derive the individual DK key of the OBU on-board device from the MK key for the entire system (step 4) and can use it for further communication, e.g. as Encryption Key or Access Credential Key (step 5). .

[0017] At the end of communication 5, the RSE roadside device generates, for example, a randomly new Div output code, and calculates the associated individual DK key (step 6). In step 7, the RSE roadside navigation device sends this pair (Div, DK) to the OBU on-board device. The OBU on-board device writes the received pair (Div, DK) to use it at the next or at least one of the next 2-5 communication, no matter whether it is with this or with another roadside RSE in its path.

[0018] Figs. 3 and 4 show an alternative embodiment, with the same reference symbols indicating the same elements. The OBU on-board device contains here a pool (Pool) of 8 pairs of different Divi output codes and the associated individual DKi keys. Resource 8 can be calculated in advance eg during the initialization or release of an OBU on-board unit in the programming station (OBU Programming Station, OPS) from the MK system code and can be stored in the OBU on-board device.

[0019] After the BST request by the RSE roadside navigation device, the OBU on-board device now selects randomly (or pseudo) in step 9 ("randomize i") (Divi, DKi) from its resource 8 and sends the Divi output code of the selected pair in response VST to the road navigation device (step 10). Alternatively, the pair (Divi, DKi) can also be selected according to specific rules from

-8 lists of pairs in a resource of 8, e.g. first, the oldest or oldest used pair. The RSE roadside navigation device can now again in step 4 with the MK key for the entire system and the received Divi lead code derive the corresponding individual DKi key and can use it for further communication 5.

[0020] Optionally, the embodiments of Figs. 1, 2 and 3, 4 may be combined with each other. And so the RSE navigational device in the embodiment of Figs. 3, 4 could, in analogy to step 6, generate a new pair (Divj, DKj) for example at the end of communication - when it has enough time, i.e. traffic flow with this and with other OBU on-board devices is just small - and analogously to step 7, it can be sent to OBU on-board device, which received pair (Divj, DKj) will save for later use in resource 8 - replacing already used pair or adding to current pairs.

[0021] The invention is not limited to the embodiments shown, but includes all variants and modifications that fall within the scope of the appended claims.

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