Method for Detecting a Speed Violation of a Vehicle

• US 20130266139A1
• Filed: 04/05/2013
• Published: 10/10/2013
• Est. Priority Date: 04/06/2012
• Status: Active Grant

• Current Assignee: Kapsch TrafficCom AG (Datax Handelsgmbh)
• Original Assignee: Kapsch TrafficCom AG (Datax Handelsgmbh)
• Inventors: Abl, Alexander, Horster, Patrick, Rass, Stefan, Schartner, Peter
• Granted Patent: US 8,964,984 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: G08G 1/054 photographing overspeeding vehicles
• CPC Class Codes: H04L 2209/84 Vehicles
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0847 involving identity based encryption [IBE] schemes
• CPC Class Codes: H04L 9/3073 involving pairings, e.g. identity based encryption [IBE], bilinear mappings or bilinear pairings, e.g. Weil or Tate pairing

Abstract

Detecting a speed violation of a vehicle traveling from a first roadside system to a second roadside system comprises: protecting evidence data collected at two roadside systems by encrypting each set of data with random session keys at each roadside system, and then encrypting the random session keys with a public key generated from an identity that may include a vehicle identifier and a timestamp. A ratio of the public keys is calculated and used to detect a violation, whereupon a private key is obtained for decrypting at least one of the encrypted session keys, and decrypting at least one of the encrypted evidence data with the decrypted session key.

Claims

1. A method for detecting a speed violation of a vehicle traveling from a first roadside system to a second roadside system, comprising:

setting-up private and public parameters, including a common modulo basis, of an identity based encryption (IBE) scheme in a key generation center and the first and second roadside systems;

capturing first evidence data comprising a first identifier of the vehicle and a first timestamp at the first roadside system, using a first identity comprising the first identifier and the first timestamp to generate a first IBE public key, encrypting the first evidence data with a first random session key, encrypting the first random session key with the first IBE public key, and deleting the first evidence data and the first session key at the first roadside system;

capturing second evidence data comprising a second identifier of the vehicle and a second timestamp at the second roadside system, using a second identity comprising the second identifier and the second timestamp to generate a second IBE public key, encrypting the second evidence data with a second random session key, encrypting the second random session key with the second IBE public key, and deleting the second evidence data and the second session key at the second roadside system;

calculating a ratio of the first and second public keys, modulo the common modulo basis, and looking-up the ratio in a table of ratios pre-computed for a set of time differences between said first and second timestamps which set represents speed violations, and, when the look-up is successful;

retrieving at least one IBE private key for at least one of said IBE public keys from the key generation center, decrypting at least one of said encrypted session keys with said private key, and decrypting at least one of said encrypted evidence data with said decrypted session key.

2. The method of claim 1, wherein the IBE scheme is a Boneh-Franklin encryption scheme.

3. The method of claim 1 wherein the evidence data is encrypted with the session key according to a symmetric encryption scheme.

4. The method of claim 3, wherein the symmetric encryption scheme is the advanced encryption standard.

5. The method of claim 1 wherein the first and second roadside systems share at least one random or pseudorandom value, and wherein the first identity and the second identity further comprise the at least one random or pseudorandom value.

6. The method of claim 5, wherein the first IBE public key is generated in the form

PK_1,t:

=g<sup>((LPN∥

pad)⊕

Ri)∥

t</sup> mod p_G

with

PK_1,t being the first IBE public key,

LPN, t being the identifier and timestamp of the first evidence data,

R_i being the random or pseudorandom value,

g, p_G being public parameters of the IBE scheme, ((LPN∥

pad)⊕

R_i)∥

t being the first identity,

and the second IBE public key is generated in the form

PK_2,t;

=g<sup>((LPN∥

pad)⊕

Ri)∥

t</sup> mod p_G

with

PK_2,t being the second IBE public key,

LPN, t being the identifier and timestamp of the second evidence data,

R_i being the random or pseudorandom value,

g, p_G being public parameters of the IBE scheme, and ((LPN∥

pad)⊕

R_i)∥

t being the second identity.

7. The method of claim 6, wherein the ratio is calculated in the form

PK_2,t·

PK_1,t<sup>−

1</sup>(mod p_G).

8. The method of claim 5 wherein the first and second roadside systems communicate to synchronously switch from one pseudorandom value to a subsequent pseudorandom value in a series of pseudorandom values.

9. The method of claim 1 wherein the first evidence data further comprises a picture of the vehicle taken with a camera at the first roadside system, and the second evidence data further comprises a picture of the vehicle taken with a camera at the second roadside system.

10. The method of claim 1 wherein the first evidence data is cryptographically signed with a signature key of the first roadside system, and the second evidence data is cryptographically signed with a signature key of the second roadside system.

11. The method of claim 1 wherein the session key has at least 128 bits.

12. The method of claim 1 wherein the first and second IBE public keys, the encrypted first and second session keys and the encrypted first and second evidence data are deleted after a predetermined period of time.

13. The method claim 1 wherein the first evidence data further comprises a class of the vehicle captured at the first roadside system.

14. The method of claim 13 wherein different tables of ratios are pre-computed for different classes of vehicles and the table used for the look-up is chosen according to the captured class of the vehicle.

15. The method of claim 1 wherein at least one of the first or second evidence data further comprises a weather or road condition captured at the first or second roadside system, and wherein different tables of ratios are pre-computed for different conditions and the table used for the look-up is chosen according to the captured condition.

16. The method of claim 1 wherein the first IBE public key is sent to the second roadside system or the second IBE public key is sent to the first roadside system for calculating the ratio.