GB2353620A

GB2353620A - Security system

Info

Publication number: GB2353620A
Application number: GB9920190A
Authority: GB
Inventors: Michael Koblbauer
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 1999-08-27
Filing date: 1999-08-27
Publication date: 2001-02-28
Also published as: GB9920190D0

Abstract

A challenge-response security system suitable for a vehicle 10 is disclosed. The system comprises a security control unit 12 which communicates with a remote transponder 14. The security control unit 12 is arranged in use to send out a challenge signal when it determines that the transponder 14 is likely to be in the proximity of the vehicle 10. So as to reduce the likelihood of challenge response pairs being bugged during the time it takes to run the information bus 22 up to its operating condition, a batch of challenge signals are pre-generated by a random number generator 16 forming part of the security control unit 12 and are pre-loaded into a memory 26 of the door module 18. When a door handle 24 is operated, the door module 18 sends the pre-loaded challenge signals out in sequence to the transponder 14. This also helps reduce the propagation delay which might exist if a user had to wait for the information bus 22 to become fully operational.

Description

2353620 A Securitv System This invention relates to security systems and

in particular to a challengeresponse security system which is suitable for use in a vehicle.

It is known to provide security systems which operate upon the so-called challenge-response principal, such as might be used for a passive entry system for a vehicle. It is a problem with such systems, that they are sometimes attacked by illegal means in an attempt to relay signals between the protected area security controller and a remote transponder so as try and defeat the security system.

It is an object of this invention to provide an improved security system.

Accordingly, the invention provides a challenge-response security system comprising a security control means arranged in use to send out internally generated challenge signals, wherein at least one said challenge signal is pregenerated by said control means and pre-loaded into a memory means in which said pre-loaded challenge signal is stored until access to a protected feature is requested, said pre-loaded challenge signal then being retrieved from said memory means and being sent out.

Said control means may pre-load a sequence of said challenge signals into said memory means, said pre-loaded challenge signals being sent out in substantially the same sequence as they were pre-loaded into the memory means.

On or after a pre-loaded challenge signal has been sent out, the control means may pre-generate a fresh challenge signal and pre-load said fresh challenge signal into said memory means. Said fresh pre-loaded challenge signal may be sent out in preference to one or more earlier pre-loaded challenge signals.

The system may further comprise a remote transponder arranged in use to receive said challenge signals and to send out response signals, wherein a transmission of a pre-loaded said challenge signal may include a signal portion which enables said remote transponder to determine the sequence number of said challenge signal, such that said remote transponder can indicate with which sequence number pre-loaded challenge signal its response signal is related.

Said challenge signals may be generated by a random number generator.

Said memory means may be connected with a security module which is located remotely from said security control means and is in communication with said security control means by means of an information bus, said security module being arranged in use to detect desired access to a protected feature and, upon such detection, automatically and unilaterally to summon a said pre-loaded challenge signal from said memory means and to send it out.

Said security module may comprise a closure member module of a vehicle and, furthermore, the security system may comprise a security system of a vehicle.

The invention will now be described by way of example only and with reference to the accompanying drawing, in which:

Figure 1 is a schematic diagram of a vehicle which includes a security system according to the invention.

Referring to the figure, a vehicle 10 includes a security system comprising a security control unit 12 and a portable transponder 14. The security control unit 12 further compriges a random number generator 16 which it 12 uses to internally generate security challenge signals.

The security challenge signals are communicated to a security module in the form of a door control module 18 which is included in a door 20 of the vehicle 10. The challenge signals are communicated to the door module 18 from the security control unit 12 via an information bus 22.

The door 20 further comprises a door handle 24 which includes a microswitch for indicating to the door module 18 when the handle 24 has been operated from outside the vehicle 10. Operation of the door handle 24 indicates the likely presence of the remote transponder 14 in the proximity of the vehicle 10 and causes the door module 18 to send out a challenge signal, as described in more detail below.

If the remote transponder 14 is in the proximity of the vehicle 10 and it successfully receives the legitimate challenge signal, it 14 sends out a security response signal. The response signal is picked up by the door module 18 and is communicated via the information bus 22 to the security control unit 12, so that it 12 can perform the necessary security functions such as allowing access to the vehicle 10 and re-enabling vehicle systems (not shown) as appropriate.

The door module 18 includes a memory 26 and the security control unit 12 is arranged, on actual or perceived departure from the vehicle 10 of the remote transponder 14, to use its random number generator 16 to pre-generate a plurality of ready made random challenge signals, which are then pre-loaded into the memory 26.

As challenge signals are pre-loaded into the memory 26, they are assigned a sequence number which is indicative of the order in which they were preloaded and they are sent out substantially in sequence according to their respective sequence numbers each time the door handle 24 is operated. In other words, each time one of these pre-loaded challenge signals is used up, the door module 18 collects the next one in the sequence from its memory 26, in readiness for the next time the door handle 24 is operated. This is done automatically and unilaterally by the door module 18, which means that there is no need for the door module 18 5 to initiate the bus 22 so as to contact the security control unit 12.

When the door module 18 sends out one of these pre-loaded signals, it includes information within the transmission to inform the transponder 14 of the sequence number of the pre-loaded challenge signal which is being transmitted. In this manner, the transponder 14 can -include in its response signal confirmation that it is responding to the challenge signal having that place in the sequence of pre-loade d challenges. This means that the security control unit 12 can derive the particular challenge signal with which it should compare that particular response signal.

When a pre-loaded challenge is used up, a fresh challenge is generated from the security control unit random number generator 16 and passed along the information bus 22 to "top-up"/replenish the store of pre-loaded challenges in the memory 26 of the door module 18.

It is preferable that, if no valid response signal is received in reply to a challenge, the next challenge to be sent out from the door module should be the latest loaded challenge, i.e. the "freshest" or top-up challenge. This will further reduce the possibility that challenge-response pairs might be bugged and captured, by for example externally monitoring the information bus 22 while it is being initiated or "woken-up", so that they can be played back illegally later on.

The fact that the challenges are pre-loaded into a memory 26 in the door module 18 also reduces reaction time of the system which might otherwise be influenced by the run-up time of the information bus. In this manner, propagation delays are reduced.

Whilst the embodiment described above concerns a specific example of the invention as applied to a passive entry system, the scope of the invention is not limited to only such passive entry systems. This invention can be applied to any system which uses a challenge-response type of arrangement. For example, the issue of a challenge from the vehicle could be initiated by a user who sends an c'unlocle' request using a manual button on a transponder in a known fashion. Receipt of such an "unlock" request could cause the issue of a challenge signal which itself requires the transponder to provide a response signal to confirm that it is indeed an authorised transponder for that particular vehicle. The issue of a challenge signal could similarly be initiated using a swipe card type of arrangement.

Claims

-6CLAIMS

A challenge-response security system comprising a security control means arranged in use to send out internally generated challenge signals, wherein at least one said challenge signal is pre-generated by said control means and pre-loaded into a memory means in which said pre-loaded challenge signal is stored until access to a protected feature is requested, said pre-loaded challenge signal then being retrieved from said memory means and being sent out.
2. A system according to Claim 1, wherein said control means pre-loads a sequence of said challenge signals into said memory means, said preloaded challenge signals being sent out in substantially the same sequence as they were pre-loaded into the memory means.
3. A system according to Claim 1 or Claim 2, wherein, on or after a preloaded challenge signal has been sent out, the control means pregenerates a fresh challenge signal and pre-loads said fresh challenge signal into said memory means.
4. A system according to Claim 3 when dependent on Claim 2, wherein said fresh pre-loaded challenge signal is sent out in preference to one or more earlier pre-loaded challenge signals.
5. A system according to any one of Claims 2 to 4, further comprising a remote transponder arranged in use to receive said challenge signals and to send out response signals, wherein a transmission of a pre-loaded said challenge signal includes a signal portion which enables said remote transponder to determine the sequence number of said challenge signal, such that said remote transponder can indicate with which sequence number preloaded challenge signal its response signal is related.
6. A system according to any preceding claim, said challenge signals being generated by a random number generator.
7. A system according to any preceding claim, said memory means being connected with a security module which is located remotely from said security control means and is in communication with said security control means by means of an information bus, said security module being arranged in use to detect desired access to a protected feature and, upon such detection, automatically and unilaterally to summon a said pre-loaded challenge from said memory means and to send it out.
8. A system according to Claim 7, said security module comprising a closure member module of a vehicle.
9. A security system substantially as described herein with reference to the accompanying drawing.
10. A security system according to any preceding claim, comprising a security system of a vehicle.