Method for issuing authorisation tickets in an intelligent transport system

Abstract

The present application discloses a method of issuing pseudonymous authorisation tickets to nodes of a cooperative ITS, for signing messages, comprising: receiving a ticket request from a node in an authorisation server, and sending a validation request to an enrolment server, conducting a validity check in the enrolment server, and, when the validity check is passed, incrementing a counter value of a counter assigned to an account at an account server enrolled with the enrolment server for the requesting node, sending a validation message to the authorisation server, and issuing a pseudonymous authorisation ticket from the authorisation server to the requesting node, repeating the aforementioned steps until a predetermined charging period expires, and, upon expiry, sending, from the enrolment server to the authorisation server, said counter value, and sending a charging request calculated from said counter value from the authorisation server to the account server for charging said account.

Claims

1. A method for issuing pseudonymous authorisation tickets to nodes of a cooperative intelligent transport system (ITS), which nodes exchange messages, each of which is signed with one of said pseudonymous authorisation tickets, the method comprising: a) receiving a ticket request from a node in an authorisation server of the ITS, which ticket request contains enrolment credentials of the requesting node, wherein the enrolment credentials are encrypted with a public key of an enrolment server of the ITS, and sending from the authorisation server a validation request containing the requesting node's enrolment credentials to the enrolment server; b) decrypting the enrolment credentials contained in the validation request with a respective private key in the enrolment server, conducting, in the enrolment server, a validity check which is only passed when both the requesting node identified by the decrypted enrolment credentials and, for the requesting node, an account at an account server are enrolled with the enrolment server, and, in case the validity check is passed, incrementing, in the enrolment server, a counter value of a counter assigned to said account and sending, from the enrolment server to the authorisation server, a validation message validating the validation request of the authorisation server; c) issuing, when the validation message validating the validation request of the authorisation server is received in the authorisation server, one of said pseudonymous authorisation tickets to the requesting node; d) repeating steps a) to c) until a predetermined charging period expires, and, upon expiry, sending, from the enrolment server to the authorisation server, a message containing said counter value and an identifier for said account, calculating, from the counter value received in the authorisation server, a charging request for the account identified by the received identifier, and sending the charging request from the authorisation server to the account server for charging said account.

2. The method according to claim 1, wherein the account at the account server is enrolled with the enrolment server for more than one node.

3. The method according to claim 1, wherein the account at the account server is enrolled with the enrolment server for a single node.

4. The method according to claim 1, wherein step c) further comprises storing the received validation message in a database of the authorisation server.

5. The method according to claim 1, wherein the message containing the counter value and the identifier for the account is digitally signed by the enrolment server prior to sending.

Description

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

(1) The disclosed subject matter shall now be explained in more detail below on the basis of exemplary embodiments thereof with reference to the accompanying drawings, in which:

(2) FIG. 1 shows a cooperative intelligent transportation system in a schematic block diagram; and

(3) FIG. 2 shows the method embodiment for issuing pseudonymous authorisation tickets to nodes of the cooperative intelligent transport system of FIG. 1 in a sequence diagram.

DETAILED DESCRIPTION

(4) FIG. 1 shows an example of a cooperative intelligent transportation system (“ITS”) 1, e.g., an ITS 1 according to the European Strategy on Cooperative Intelligent Transport. Systems (“C-ITS”). Within the ITS 1, the method shown in FIG. 2 is performed. The ITS 1 comprises a plurality of nodes N.sub.1. N.sub.2, . . . generally N.sub.i, that exchange messages M.sub.1, M.sub.2, . . . generally M.sub.k. Each node N.sub.i is, e.g., a vehicle or an infrastructure device such that the exchange of messages M.sub.k allows road users and traffic managers of the ITS 1 to share information, e.g., by vehicle-to-vehicle (“V2V”) and/or by vehicle-to-infrastructure (“V2I”) communication.

(5) As will be explained in greater detail below in the context of FIG. 2, the ITS 1 comprises at least one enrolment server (also: “enrolment authority”) EA and at least one authorisation server (also: “authorisation authority”) AA. The ITS 1 optionally further comprises at least one root certificate authority RCA which approves (arrows 2 and 3, respectively) both the authorisation server AA and the enrolment server EA, and an optional trust list manager TLM for enabling (arrow 4) the root certificate authority RCA. Moreover, the ITS 1 comprises at least one of one or more operators/manufacturers OM and one or more account servers AS, wherein each account server AS keeps one or more accounts AC.sub.1, AC.sub.2, . . . , generally AC.sub.m, each for one or more nodes N.sub.i and, when the ITS 1 comprises more than one authorisation server AA, for one or more authorisation servers AA. For communication between the enrolment server EA, the authorisation server AA, the operator/manufacturer OM, the account server AS, and the nodes N.sub.i, the ITS 1 has communication links L, e.g., wire-bound and/or wireless communication links L. Each communication link L may either be direct or via intermediate nodes N.sub.i.

(6) Each message M.sub.k exchanged in the ITS 1 shall be authenticated for controllability and for preventing manipulation. At the same time, privacy of the nodes N.sub.i shall be kept. For achieving both, each message M.sub.k is signed with a pseudonymous authorisation ticket AT.sub.1, AT.sub.2, . . . , generally AT.sub.n (FIG. 2). The method of issuing these authorisation tickets AT.sub.n shall now be explained in detail with reference to FIG. 2.

(7) Each node N.sub.i is identified in the enrolment server EA by means of enrolment credentials EC which are suitable to unambiguously identify the node N.sub.i. In the example shown in FIG. 2, in a first step 5 of the method the operator/manufacturer OM registers information on each node N.sub.i—including the enrolment credentials EC thereof—with the enrolment server EA as known from, e.g., C-ITS. In another embodiment, the enrolment credentials EC may be generated by the node N.sub.i itself or provided to the node N.sub.i, e.g., by the operator; manufacturer OM, and are then shared with the enrolment server EA.

(8) In step 6, the account server AS registers the respective account AG.sub.m for each node N.sub.i and, in case of more than one authorisation server AA, for at least one authorisation server AA with the enrolment server EA. In an optional embodiment when the account server AS is run by the operator/manufacturer OM such that it is integrated therein, steps 5 and 6 may be merged. Again, the account AC.sub.m for a node N.sub.i may alternatively be shared with the enrolment server EA by the node N.sub.i itself, e.g., after having been provided therewith by the account server AS. In an alternative embodiment, the account server AS is run by the enrolment server EA such that it is integrated therein; in this case, step 6 may not be required, e.g., when the node N.sub.i itself registers its respective account AC.sub.m with the enrolment server EA, for example, during enrolment as described below.

(9) In step 7, the account server AS registers with the authorisation server AA. This registration may be notified to the enrolment server EA in step 8 either upon registration or upon a later request by the enrolment server EA. In another embodiment this registration with the authorisation server AA and/or the notification thereof to the enrolment server EA may be a precondition for approving the account server AS in the ITS 1 such that steps 7 and/or 8 are unnecessary.

(10) After registration, the node N.sub.i sends an enrolment request (step 9) to the enrolment server EA. When the node N.sub.i is identified based on said registered information the enrolment server EA sends back the enrolment credentials EC, and the respective account AC.sub.m at the account server AS is enrolled for the node N.sub.i (step 10). The enrolment credentials EC of each node N.sub.i may be changed occasionally or regularly.

(11) For having an authorisation ticket AT.sub.n issued after enrolment, the node N.sub.i sends a ticket request TR to the authorisation server AA in step 11. The ticket request TR contains the enrolment credentials EC of the requesting node N.sub.i, i.e., of the node N.sub.i which sends the ticket request TR. The enrolment credentials EC of the requesting node N.sub.i are encrypted by the requesting node N.sub.i with a public key K.sub.pu of the enrolment server EA. The public key K.sub.pu is part of an asymmetric encryption scheme as known in the art; therein, data encrypted with said public key K.sub.pu can only be decrypted with a respective private key K.sub.pr of the enrolment server EA, which private key K.sub.pr—being “private”—is only known to the enrolment server EA. Hence, the authorisation server AA has no access to the encrypted enrolment credentials EC and, particularly, cannot derive any information on the identity of the requesting node N.sub.i therefrom.

(12) After receiving a ticket request TR, the authorisation server AA generates, in step 12, a validation request VR which contains the encoded enrolment credentials EC of the requesting node N.sub.i. In some embodiments, the validation request VR contains further parts of the ticket request TR or even the complete ticket request TR of the requesting node N.sub.i. In step 12, the authorisation server AA also sends the generated validation request VR to the enrolment server EA for validation. Upon reception of said validation request VR, the enrolment server EA conducts a validity check 13.

(13) The validity check 13 comprises at least the following criteria of validity that are checked independently from each other, i.e., in any sequence and/or in parallel. A first criterion is checked in step 14 and concerns the enrolment of the requesting node N.sub.i such that the first criterion is only satisfied when the requesting node N.sub.i identified by the decrypted enrolment credentials EC is enrolled with the enrolment server EA: otherwise, the validity check 13 is not passed. A second criterion is checked in step 15. The second criterion is only satisfied when the account AC.sub.m at the account server AS is enrolled with the enrolment server EA for the identified requesting node N.sub.i. Further criteria may be checked in the validity check 13, e.g., that the account server AS is registered with the authorisation server AA when this is not a precondition in the ITS 1. Only when all criteria are satisfied, the validity check 13 is passed; otherwise, the validity check 13 is not passed.

(14) To each account AC.sub.m enrolled with the enrolment server EA a separate counter CT.sub.1, CT.sub.2, . . . , generally CT.sub.m, is assigned. When the validity check 13 is passed, the enrolment server EA, in step 16′, increments a counter value CV of that counter CT.sub.m in the enrolment server EA which is assigned to the account AC.sub.m enrolled with the enrolment server EA for the requesting node N.sub.i. Moreover, the enrolment server EA validates the validation request VR, e.g., by sending a validation message VM to the authorisation server AA in step 16″ in reply to the validation request VR, when the validity check 13 has been passed. When, on the other hand, the validity check 13 has not been passed, the enrolment server EA does not increment the counter CT.sub.m and does not validate the validation request VR, e.g., by not sending a message to the authorisation server AA in reply to the validation request VR (implicitly), or by sending a message that is different from the validation message VM to the authorisation server AA in reply to the validation request VR (explicitly).

(15) When the authorisation server AA receives the validation message VM in reply to the validation request VR, i.e., when the validation request VR was validated by the enrolment server EA, the authorisation server AA generates and issues a pseudonymous authorisation ticket AT.sub.n to the requesting node N.sub.i in step 17. In an optional step 18, the authorisation server AA stores the received validation message VM in a database 19 thereof for later plausibility check and/or dispute resolution.

(16) It shall be noted that the requesting node N.sub.i identifies itself vis-à-vis the authorisation server AA for addressability, by means of a one-time identifier or the like as known in the art, such that the true identity of the node N.sub.i remains undisclosed to the authorisation server AA.

(17) After having received the issued authorisation ticket AT.sub.n from the authorisation server AA, the requesting node N.sub.i can use the authorisation ticket AT.sub.n once or several times to sign and thereby pseudo-anonymise messages M.sub.1, M.sub.2, . . . , M.sub.k that the node N.sub.1 sends to other nodes N.sub.i+1, N.sub.i+2, . . . , see steps 20 to 22.

(18) Until a predetermined charging period CP expires, said sending and receiving ticket requests TR, validation requests VR and validation messages VM and said issuing authorisation tickets AT.sub.n is repeated (arrow 23). Upon expiry of the charging period CP, the enrolment server EA sends a message ME to the authorisation server AA (step 24), which message ME contains the counter value CV of the counter CT.sub.m assigned to said account AC.sub.m and an identifier I.sub.AC of the account AC.sub.m at the account server AS. It is understood that, when the ITS 1 has more than one account server AS, the account server AS which keeps said account AC.sub.m is also indicated by the identifier I.sub.AC.

(19) As the ITS 1 comprises a multiplicity of nodes said message ME contains, in one embodiment, the counter values CV of some or all counters CT.sub.m respectively assigned to the accounts AC.sub.m of some or all requesting nodes and the respective identifier I.sub.AC; in an alternative embodiment, the enrolment server EA sends a separate message ME for each counter value CV and account AC.sub.m which the respective counter CT.sub.m is assigned to. Optionally, the message ME is digitally signed by the enrolment server EA prior to sending. After sending said message ME, the counter value CV of each counter CT.sub.m in the enrolment server EA is optionally reset for a subsequent charging period CP.

(20) In step 25, the authorisation server AA calculates, from each received counter value CV, e.g., by means of an agreed multiplier, a respective charging request CR for the account AC.sub.m identified by the received identifier I.sub.AC. Then, the authorisation server AA sends the charging request CR to the account server AS for charging each of said accounts AC.sub.m. Thereby, the issuing of authorisation tickets AT.sub.n is charged.

CONCLUSION

(21) It shall be noted that the communication between nodes N.sub.i, the authorisation server AA, the enrolment server EA, the operator/manufacturer OM and/or the account server AS is optionally encrypted by further keys of a symmetric or an asymmetric encryption scheme as known in the art. Thus, the disclosed subject-matter is not restricted to the specific embodiments described in detail herein, but encompasses all variants, combinations and modifications thereof that fall within the framework of the appended claims.