AU4241999A

AU4241999A - A security system

Info

Publication number: AU4241999A
Application number: AU42419/99A
Authority: AU
Inventors: Not Given Name
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-08-27
Filing date: 1999-08-02
Publication date: 2000-03-09
Also published as: KR20010079689A; JP2002525463A; EP1108102A1; BR9913320A; WO2000012846A1; DE59913526D1; EP1108102B1

Description

I Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: ROBERT BOSCH GmbH of Postfach 30 02 20, D-70442 Stuttgart, Germany *Actual Inventor(s): Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, of 1 Little Collins Street, Melbourne, Victoria 3000, Australia Invention Title: "A SECURITY SYSTEM" Details of Associated Provisional Application Nos: PP5515/98 and PP7489/98 The following statement is a full description of this invention, including the best method of performing it known to us: o*oe o performing it known to us: -1- I I P:\OPER\DBW\PP5515.98 218/99 -2- A SECURITY SYSTEM The present invention relates to a security system, and in particular to a passive security system for vehicles.

Current passive security systems for entry or activation of vehicles use a remote 10 electronic key which incorporates a transmitter that transmits authentication data to a receiver "located in the vehicle, when the key is within a predetermined range from the receiver. The communications protocol executed between the transmitter and the receiver uses a radio frequency interface to carry the transmitted data. The radio frequency (rf) interface has a .limited range, to ensure the communication link is broken when a holder of the key moves 15 away from the immediate vicinity of the vehicle.

."Passive security systems are susceptible to attack by unauthorised persons using intercepting equipment, placed in the vicinity of the vehicle and the key, to receive the transmissions sent by the key and relay the transmissions to the vehicle or record the S020 transmissions. Once intercepted, the transmissions can be demodulated to obtain the data transmitted. An unauthorised person can acquire an authentic key from a manufacturer and use the transmitted data with the acquired key as a duplicate key. This duplicate key may then be used to gain unauthorised access to and/or use of the vehicle. It is desired to provide a system which obviates this problem or at least provides a useful alternative.

In accordance with the present invention there is provided a security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, characterised in that said transmitter transmits identification data unique to said key, said identification data being embedded in hardware of said transmitter, and said security system grants an authority for said secure object on transmission of said authentication data when the identification data transmitted corresponds to identification data of said receiver.

P:\OPER\DBW\PP5515.98 2/8/99 -3- The present invention also provides a security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, said authentication data being included in a response message transmitted by said key in response to a challenge message received from the secure object, characterised in that at least part of said response message must be received within an acceptance time window for said security system to grant an authority for said secure object, said acceptance window beginning at a predetermined period of time from the start of transmission of said challenge message.

S 10 The present invention also provides a security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, characterised in that the communications protocol executed by said transmitter and receiver detects transmission of said authentication data by an unauthorised transmitter.

A preferred embodiment of the present invention is hereinafter described, by way of example only, with reference to the accompanying drawings, wherein: Figure 1 is a schematic diagram of a preferred embodiment of a security system, with an intercepting station; S" 20 Figure 2 is a block diagram of the security system; and Figure 3 is a timing diagram for signals transmitted by the security system.

A passive security system 2, as shown in the Figures, includes an electronic key 4 with a transmitter 6 and an induction coil antenna 7, a base station 8 with a receiver 10 and an induction coil antenna 12. The base station 8 is located in a secure area, such as a vehicle, and controls access to the secure area and/or starting of the vehicle. When the key 4 is brought within a predetermined range from the antenna 12 of the receiver 10, the receiver 10 excites the key 4, so as to cause the transmitter 6 to begin transmission to the receiver 10. Data is transmitted using rf signals which establish a communications link between the key 4 and the base station 8. The data transmitted between the key 4 and the base station 8 is determined by a communications protocol which the key 4 and base station 8 adhere to, and which involves the transmission of authentication data from the key 4 to the receiver 10. Access to P:\OPER\DBW\PP5515.98 2/8/99 -4the secure area and/or starting of the vehicle is only allowed by the base station 8 if the transmitted authentication data corresponds with authentication data stored by the base station 8.

An intercepting station 16 includes a receiver to also receive the transmissions from the key 4 and store or relay all signals received. The station 16 is used to demodulate the signals transmitted to obtain a copy of the transmitted data. The keys 4 are mass produced and meet the requirements dictated by vehicle manufacturers. The keys 4 include a number of security features, such as the authentication data transmitted and a unique spectral signature or characteristic third order intercept point, as discussed in the specification of Australian Patent Application No. 33933/99 by the applicant. However, an unauthorised person may be o• able to obtain one of the mass produced keys 4, and using the data obtained with the intercepting station 16, the data can be simply relayed on to the vehicle using the transmitter of the obtained unauthorised key or the data can be recorded on the unauthorised key 4 to 15 create a duplicate key 4. The duplicate key 4 could therefore be used to obtain unauthorised access to and/or use of a vehicle. In a relay attack, the intercepting station is used to excite the original key 4, which may be located in a vehicle owner's premises, and then relay the demodulated obtained data from the original key 4 to the vehicle using the transmitter of the duplicate key 4.

To prevent the above occurring, according to the preferred embodiment described hereinafter, the keys 4 are all manufactured with a unique serial number which is embedded as identification data in the key 4. The identification data is embedded by incorporating it in the mask layout design of an integrated circuit which comprises the transmitter 6 of the key 4. The identification data is incorporated in the integrated circuit such that it cannot be read by any other electronic device once fabricated. The transmitter 6 is also designed so that when the key 4 is energised by the base station 8 the identification data, which represents the serial number, is transmitted first before the transmitter commences transmission of any other data which is provided to it, such as the authentication data. For instance, the transmitter 6 will transmit all data it receives from a microcontroller 35 using a communications protocol which includes a header that is transmitted first before any data is transmitted. The transmitter 6 includes in the header the serial number of the key 4. The base station 8 maintains a copy of P:\OPER\DBW\PP5515.98 218199 the unique serial number and will only allow access to and/or use of the vehicle if: the serial number received corresponds to the stored serial number in the base station 8; and the base station 8 receives the transmitted serial number within a valid period of time.

The valid period of time corresponds to the first initial period when a transmission is received from the key 4. The valid period of time is set to allow receipt of the transmitted serial number in the initial transmission, but is also set to be short enough to detect i 10 suppression of transmission of the unique serial number of the duplicate key followed by transmission of a copied serial number from the original key. This ensures that an "unauthorised person cannot gain access to and/or use of the vehicle by transmitting the copied data, which may include the serial number of the copied original key, after suppressing the transmission of the serial number of the duplicate key. By using the communications protocol with the header transmitting the serial number, in a relay attack, the intercepting station 16 using the unauthorised key 4 will send first the header including the serial number of the S"unauthorised key, followed by the header and data obtained from the original key 4. The transmission of two headers, or in fact two serial numbers, will be detected. The valid period of time therefore corresponds to the time taken to transmit one header before any data is received. The header structure can be detected by having unique digital words at the start and stop of each header. Also the beginning of the data can be detected by having a unique data prefix. Accordingly by detecting the headers, when the header time duration detected at the receiver 10 exceeds the length of one header, then access to and/or use of the vehicle is refused.

The transmitter 6, as shown in Figure 2, includes an integrated circuit to transmit two constant tone signals, once the key 4 is excited by the receiver 10. The circuitry can include two radio frequency oscillators 30 and 32 for the tones, respectively, the outputs of which are combined in a combiner 34 for transmission on the antenna 7 of the transmitter 6.

Alternatively, the circuit may include a complex quadrature modulator that enables the generation of two tones separated by a multiple of the channel spacing used in the receiver I I_ P:\OPER\DBW\PP5515.98 2/8/99 -6- One of the tone signals, for example that generated by the first frequency oscillator is used to transmit the identification data representing the unique serial number. The key 4 includes the microcontroller 35 which provides data to the transmitter 6 for transmission.

The transmitter 6 receives the data and places it with a header including its serial number for transmission to the base station 8. The transmitter 6 includes code to establish the headers and place them with data for transmission in accordance with the communications protocol between the key 4 and the base station 8.

The receiver 10 of the base station 8 includes a radio FM receiver 36 connected to the i 10 antenna 12, an analogue/digital converter 38, a microcontroller 40, and a frequency synthesised local oscillator 42. The microcontroller 40 is programmed to control the 0..

frequency synthesiser 42, and to process data received from the A/D converter 38 and the FM receiver 36. The frequency synthesiser is used to select frequency channels to be processed by the FM receiver 36, which generates a received signal strength indicator (RSSI) output for 15 each of four channels C1 to C4, as discussed in the specification of Australian Patent Application No. 33933/99 by the applicant. The RSSI output for each channel is passed to the A/D converter for conversion into a binary word for processing by the microcontroller The microcontroller 40 treats the binary word as spectral data representative of the received energy in each of the channels CI to C4, and in turn uses the spectral data for comparison with a previously stored spectral signature for the transmitter 6.

The FM receiver 36 also demodulates the data received on one of the channels C2 or C3 which corresponds to the tone signal which transmits the transmitted identification data to obtain any header with the identification data and it forwards this to the microcontroller on a data received output. The microcontroller 40 stores a copy of the unique serial number of the authorised original key 4 as identification data, and uses this stored data to compare with the transmitted identification data.

The system 2 is initiated by placing the key 4 within the predetermined range from the antenna 12 so as to excite the key 4 and cause a transmission of the two fundamental tones and the unique serial number. The spectral data and serial number received by the microcontroller is then stored as the spectral signature and serial number of the transmitter 6 for future P:\OPER\DBWPP5515.98 2/8/199 -7comparison for all subsequent communications between the key 4 and the receiver The key 4 and the base station 8 accordingly execute the following steps when a communication link is subsequently established: Prior to the transmission of any authentication data, the two fundamental tones in channels C2 and C3 are simultaneously transmitted with the serial number in one of the channels C2 or C3.

(ii) The frequency synthesiser 42 selects the four channels Cl to C4 and the FM receiver 36 produces an RSSI output for each of the channels and a data 10 received output for the microcontroller (iii) The microcontroller 40 receives and processes the spectral data representative of the received signal levels for each of the channels, and this is compared with the stored spectral signature.

(iv) If there is any deviation between the spectral signature and the spectral data by more than the microcontroller 40 causes the base station 8 to halt the authentication procedure and prevent access to the secure area and/or use of *-the vehicle.

The microcontroller 40 processes any signals on the data received output to determine if they represent a header and include the stored serial number. If the data on the data received output does not match the stored serial number or the microcontroller 40 detects a delay, exceeding the valid period of time, between executing step (iii) and receipt of data that does match the stored serial number data, the microcontroller 40 causes the base station 8 to halt the authentication procedure and prevent access to the secure area and/or starting of the vehicle. The delay corresponds to any attempted prevention or suppression of transmission of the serial number when a duplicate key 4 is initially excited. More particularly, the delay corresponds to the receipt of more than one header before data to be processed is received, according to the communications protocol.

(vi) The level of deviation between received spectral data and the spectral signature is recorded for subsequent analysis to determine a characteristic third order interception point to identify an attacking station. Any received unauthorised P:\OPER\DBW\PP5515.98 218199 -8serial number of an unauthorised key is also stored to identify the unauthorised key. The number of attacks can also be stored.

(vii) When the base station 8 subsequently detects an authorised user and allows authorised access and/or starting of the vehicle, the microcontroller 40 causes generation of a warning signal to indicate an attack has been made. The warning signal may be in a form of a displayed message, a warning lamp or an audio signal generated in the secure area, i.e. the vehicle.

To excite the key 4, the base station 8 includes an FM transmitter 37 which uses the 10 antenna 12 in order to forward challenge data 50 to a receiver 9 of the key 4. The challenge data 50, as shown in Figure 3, is sent at a time TSTAR

T

at which time the receiver 36 of the base station 8 may begin measuring the valid period of time within which to receive the authentication data from the key 4. The key 4 transmits the authentication data and the serial number on one of the available channels C2 and C3 in a response message 52, as shown in Figure 3. The response message 52 is sent during or after transmission of the challenge message 50. At least part of the response message 52 needs to be received by the base station 8 within an acceptance time window 54 between times TMN and TMA x The frequency channel C2 and C3 used is selected by data contained in the challenge message 50. The time TSTART corresponds to the start 56 of the challenge data 50, and the response 52 needs to be valid and at least partly received no earlier than TM N and no later than TMA

X

If a response 58 is received outside of the time window 54, it is automatically an invalid response 58. The beginning of the time window 54, TMI, may be at TSTART or during or after the challenge message 50 or at the end of the challenge message 50, as shown in Figure 3. TMAX is about 1 millisecond from TMr

N

so that the acceptance window 54 is about 1 millisecond. This is particularly advantageous as any unauthorised user with an attacking station 16 will need at least 2 to 5 milliseconds to determine the transmission frequency for the response 52 in order to intercept the response 52. The time window 54 is accordingly positioned to detect only valid responses 52 and not delayed invalid responses 58 produced by an attacking station 16.

Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention as herein described with reference to the accompanying drawings.

Claims

1. A security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, characterised in that said transmitter transmits identification data unique to said key, said identification data being embedded in hardware of said transmitter, and said security system grants an authority for said secure object on transmission of said authentication data when the identification data transmitted corresponds to identification data of said receiver.

2. A security system as claimed in claim 1, wherein said authority is granted when said S..identification data is received within a valid period of time and corresponds to said identification data of said receiver.

3. A security system as claimed in claim 2, wherein said identification data is transmitted in a header of a communications message between said receiver and transmitter and said header must be received within said valid period of time to grant said authority.

4. A security system as claimed in claim 3, wherein said header is transmitted by said key in a response message to a challenge message received from the secure object, and at least part of said response message must be received within said valid period of time to grant said authority. A security system as claimed in claim 4, wherein said valid period of time is an acceptance window which begins at or a predetermined period of time from the start of transmission of said challenge message.

6. A security system as claimed in claim 5, wherein said predetermined period of time is less than or equal to the length of said challenge message.

7. A security system as claimed in claim 6, wherein said acceptance window is about 1 millisecond. 1~_1 _I I_ P:\OPER\DBW\PP5515.98 2/8199

8. A security system as claimed in any one of the preceding claims, wherein said transmitter includes an integrated circuit in which said identification data is embedded.

9. A security system as claimed in any one of the preceding claims, wherein said transmitter accesses and transmits said identification data when commencing a transmission to the receiver. A security system as claimed in claim 9, wherein said unique identification data represents a serial number for said key and is automatically transmitted irrespective of other i 10 data provided to the transmitter for transmission.

11. A security system as claimed in claim 9 when dependent on at least claim 2, wherein said transmitter transmits a tone signal which the receiver converts to spectral data, and said security system grants said authority on transmission of said authentication data when the 15 spectral data corresponds to a spectral signature of said transmitter, and the identification data transmitted corresponds to identification data of said receiver and is received within said valid period of time. C

12. A security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, said authentication data being included in a response message transmitted by said key in response to a challenge message received from the secure object, characterised in that at least part of said response message must be received within an acceptance time window for said security system to grant an authority for said secure object, said acceptance window beginning at a predetermined period of time from the start of transmission of said challenge message.

13. A security system as claimed in claim 12, wherein said predetermined period of time is less than or equal to the length of said challenge message.

14. A security system as claimed in claim 12 or 13, wherein said acceptance window is about 1 millisecond. M 0 P:\OPER\DBWPP5515.98 2/8/99 11 A security system as claimed in any one of the preceding claims, wherein said authority allows access to said secure object.

16. A security system as claimed in claim 15, wherein said secure object is a vehicle.

17. A security system as claimed in any one of claims 1 to 14, wherein said secure object is a vehicle and said authority allows operation of said vehicle. .18. A security system as claimed in claim 17, wherein said operation includes starting said 10 vehicle. s. a. a A security system including an electronic key having a transmitter and a secure object having a receiver, said transmitter and receiver being adapted to communicate to transmit authentication data, characterised in that the communications protocol executed by said transmitter and receiver detects transmission of said authentication data by an unauthorised transmitter. go.* A security system as claimed in claim 19, wherein said transmission by said unauthorised transmitter is detected by determining compliance with time constraints of said 20 protocol.

21. A security system as claimed in claim 19 or 20, wherein said authentication data includes identification data of said transmitter.

22. A vehicle having a security system as claimed in any one of the preceding claims. DATED this 2nd day of August, 1999 ROBERT BOSCH GmbH By its Patent Attorneys DAVIES COLLISON CAVE