EP1149361A1

EP1149361A1 - Method and system controlling access to a resource restricted to certain time slots, the acceding and accessed resources not having a real time clock

Info

Publication number: EP1149361A1
Application number: EP00900664A
Authority: EP
Inventors: Fabrice Clerc; Marc Girault
Original assignee: LA POSTE
Current assignee: LA POSTE
Priority date: 1999-02-01
Filing date: 2000-01-26
Publication date: 2001-10-31
Also published as: WO2000046757A1; FR2789203A1; FR2789203B1

Abstract

The invention concerns a method for controlling access to an electronic key for an electronic lock, within a predetermined time slot, which consists in: previous to all attempt at accessing, storing in the lock a control time value (VHS), delivered by a real time clock of an external validating entity; then, at each accessing attempt, in the key, reading a time slot (PH); storing a testing time value (VHC), delivered by the validating entity; transmitting from the key to the lock the time value (PH) and the testing time value (VHC); in the lock, verifying the conformity of the testing time value (VHC) with the time value (PH), and with the control time value VHS); in case of conformity, allowing access, and updating the control time value (VHS), from the transmitted testing time value (VHC); in case there is no conformity, access is prohibited.

Description

METHOD AND SYSTEM FOR CONTROLLING ACCESS TO A RESOURCE

LIMITED TO CERTAIN TIME RANGES, ACCESING RESOURCES

AND ACCESS WITHOUT A REAL-TIME CLOCK

The present invention relates to a method and a system for controlling access, by an accessing resource or electronic key, devoid of real time clock, to an accessed resource or electronic lock, also devoid of real time clock, this access being limited at certain time slots.

It applies to controlling access to any resource, accessed resource, the use of which is to be controlled, and the access to which is to be limited to one or more specific time slots, also called predetermined validity periods, that the resource considered is a building, a computer system, or any other object, such as a mailbox or a bank safe.

The invention applies more particularly to the control of access to accessed resources which are not autonomous in energy and / or which have only a limited potential for verifying a valid time slot, in particular resources which do not have real time clock.

The validity range can be either the actual period during which it is possible to access the resource, or any other parameter making it possible to limit in time an attack by fraudulent use of the accessing resource.

The main advantage of a logical means of access to a resource compared to a physical means of access generally lies in the possibility of allowing access to the resource only within a relatively short time slot. predetermined. Under these conditions, if the electronic key is lost, stolen, assigned or duplicated, it will not allow its illegitimate holder to access the resource outside the predetermined time slot. However, this assumes that the accessed resource is able to verify that this time range is respected. This generally implies that the resource accessed has a real time clock.

Thus, document FR-A-2 722 596 describes an access control system limited to authorized and renewable time slots by means of a portable storage medium. This system, based on cryptographic mechanisms, makes it possible to limit the period of validity of access rights to a short duration, in order to avoid illegitimate use in the event of unlawful loss, theft, transfer or duplication.

However, the solution described is based on the highly restrictive assumption that the resource accessed is energy independent, in order to maintain a real-time clock enabling it to check the validity of the time slot in which the access attempt takes place by the accessing resource.

Access control methods and systems are also known in which the accessed resource does not include a real-time clock, but only a counter, updated after a successful access attempt from the accessing resource to the accessed resource.

However, in such methods and systems, the resetting of the counter in the accessed resource is generally carried out by the accessing resource, by means of a real time clock with which the accessing resource is provided. A drawback of this solution is that it requires ensuring the energy autonomy of the accessing resource, so that the latter can permanently maintain its real time clock. The present invention aims to remedy the aforementioned drawbacks by allowing an accessed resource to verify a range of validity associated with an access right presented by an accessing resource while eliminating the need for the presence of a real-time clock, not only in the accessed resource, but also in the accessing resource.

To this end, the present invention provides a method of controlling access from at least one electronic key to at least one electronic lock, within a predetermined time range, according to which:

(a) prior to any attempt to access the electronic key to an electronic lock, a control hourly value is stored in the lock, delivered by a real time clock from an external validation entity; then, on each attempt to access the electronic key to an electronic lock: in the electronic key:

(b) a predetermined time slot is read, previously stored in the electronic key;

(c) a test hourly value stored by the real time clock of the external validation entity is stored in the key;

(d) the time range and the test time value are transmitted from the electronic key to the electronic lock, and in the electronic lock: (e) it is verified that the transmitted hourly test value is within the predetermined time range, and that it is later than the control hourly value stored in the lock; (f) if the verifications carried out in step (e) are satisfied, access is authorized, and the control hourly value is updated, from the transmitted hourly test value;

(g) if the transmitted hourly test value is outside the predetermined time range, or if it is earlier than the control hourly value stored in the lock, access to this key is prohibited.

In an embodiment which provides increased security, the following additional steps are carried out: in the electronic key:

(bl) in step (b), we read, in addition to the time slot, or instead of the time slot, an electronic signature of this time slot, previously calculated and stored in the electronic key;

(dl) in step (d), the electronic key is transmitted to the electronic lock, on the one hand, said electronic signature in addition to or instead of the time slot and, on the other hand, the hourly test value, and in the electronic lock:

(el) before step (e), the transmitted signature is verified, using a specific verification key;

(fl) in step (f), access is authorized, and the control hourly value is not updated, from the transmitted test hourly value, unless the checks carried out in steps ( el) and (e) are satisfied; (gl) in step (g), access from the key to the lock is prohibited if the transmitted hourly test value is outside the time range, or if it is earlier than the hourly value of control memorized in the lock, or if the verification carried out in step (el) is not satisfied.

Alternatively, the order of execution of steps (el) and (e) can be reversed.

The specific verification key used in step (el) can be a public or secret key.

In another particular embodiment capable of providing increased security, the following additional steps are carried out: in the electronic key: (c2) in step (c), one calculates and stores, in addition to the value test schedule, an electronic signature of this test schedule value;

(d2) in step (dl), the electronic signature of the hourly test value is also transmitted from the electronic key to the electronic lock, and in the electronic lock:

(e2) before or after step (e), the signature of the test value is verified, using a second specific public or secret verification key; (f2) in step (f), access is authorized, and the check hourly value is updated, only if the checks carried out in steps (e), (el) and (e2) are satisfied;

(g2) in step (g), access of the electronic key to the electronic lock is prohibited if one of the verifications carried out in steps (e), (el) or (e2) is not satisfied. β The introduction of an electronic signature of the test value aims to protect the electronic key and lock against a type of fraud which would consist, for a pirate with a time slot value and an hourly value d 'authentic test, to modify the hourly test value so that it becomes later than the hourly control value contained in the lock while remaining within the validity range. The aforementioned time slot may include several separate time slots.

In a particular embodiment, the time slot is an interval comprising two limits each expressed as a date in day, month, year and a schedule in hours, minutes, seconds.

The present invention also provides an electronic access control system, within a predetermined time range, comprising at least one electronic lock and at least one electronic key, in which the key comprises:

a module for memorizing a test hourly value, accessible in read and write, and

- a communication module for transmitting to the lock a predetermined time range and the test time value, and in which the lock comprises:

a module for memorizing a control hourly value, accessible in read and write, and

- a module for comparing the test hourly value with the predetermined time range and with the control hourly value stored in the lock storage module. In an embodiment which provides increased security, the communication module for transmitting to the lock a predetermined time range and the test hourly value is accompanied by a module for transmitting to the lock an electronic signature of the time slot and an electronic signature of the test hourly value, and the lock further comprises a module for verifying the electronic signatures transmitted by the key.

In a particular embodiment, the storage module comprises an electrically reprogrammable non-volatile memory.

In a particular embodiment, the electronic key communicates with the electronic lock using a contactless transmission module, by electromagnetic induction.

This contactless transmission module may include a first electromagnetic coil provided in the key and a second electromagnetic coil provided in the lock. These two windings can be concentric. The present invention also provides an electronic key comprising at least one logical key calculation unit, a transmission - reception module for key access control signals for implementing an access control method between this electronic key and an electronic lock from lock access control signals generated by this electronic lock, this key being remarkable in that it further comprises:

a module generating a power signal, controlled by the aforementioned key calculation unit; and - a key transfer module for transferring key and lock access control signals and a power signal, the key transfer module comprising at least one winding interconnected to the module generating a power signal and to the transmission - reception module.

The present invention further provides an electronic lock comprising at least one logical unit for calculating a lock and a module for transmitting - receiving lock access control signals for implementing an access control method. between this electronic lock and an electronic key from key access control signals and a power signal generated by this electronic key, this lock being remarkable in that it further comprises:

- a lock transfer module for the key and lock access control signals and the power signal, the lock transfer module comprising at least one winding interconnected with the transmission module - reception of control signals lock access; and

- a module for storing the electrical energy conveyed by the power signal, interconnected with the aforementioned winding.

Other characteristics and advantages of the present invention will appear on reading the following detailed description of particular embodiments, given by way of nonlimiting examples. The description refers to the accompanying drawings, in which: FIG. 1 is a flow diagram of the access control method of the present invention, in a first particular embodiment; - Figure 2 is a flowchart of the access control method of the present invention, in a second particular embodiment; FIG. 3 is a flowchart of the access control method of the present invention, in a third particular embodiment; FIG. 4 schematically represents the access control system of the present invention, in a first particular embodiment; FIG. 5 schematically represents the access control system of the present invention, in a second particular embodiment; - Figure 6 shows schematically the access control system of the present invention, in a third particular embodiment; FIG. 7 partially reproduces FIG. 1a of the French patent application for filing number 98 10396; and - Figure 8 shows schematically the contactless transmission module allowing the electronic key to communicate with the electronic lock, in a particular embodiment.

In the following, we consider an electronic key used for an attempt to access an electronic lock. The electronic key and lock have a calculation unit.

An external validation entity is provided with a real-time clock. This real-time clock delivers a current hourly value VH, expressed for example in day, month, year, hours, minutes, seconds.

We want to limit access from the key to the lock to a given time range PH, defined as the time interval between two determined time values VH1 and VH2: PH = [VH1, VH2], or more broadly as a meeting of such intervals: PH = [VH1, VH2] [VH3, VH4] ... [VHn-1, VHn].

As shown in FIG. 1, a first step 1001 of the method consists in storing in the electronic lock a time value VH _S , current time value delivered by the real time clock of the aforementioned validation entity. By convention, in the following, this hourly value VH _S is called "hourly control value VH _S ".

We then consider a situation where the electronic key attempts to access the electronic lock. This situation can be expressed in various ways, depending on the form and nature of the supports containing the key and the lock. By way of nonlimiting example, if the key has a tubular part or in the form of a flat tongue, the access attempt is made by introducing the tubular part into a complementary tubular cavity of the lock, or into a complementary slot, respectively.

A protocol for verifying the right of access of this key to this lock is then implemented successively in the key and in the lock.

In the key, as indicated in 1002 in FIG. 1, we read a predetermined time range PH, which has been previously stored in the electronic key.

As indicated in 1003, during the access attempt, a hourly value VH _C is stored in the key, current hourly value delivered by the real time clock of the aforementioned validation entity. By convention, in the following, this hourly value VH _C is called "hourly test value VH _C ". Then, in 1004, the range of validity PH and the hourly test value VH _C are transmitted to the lock. The following verification steps then take place in the lock.

In 1005 and 1006, one checks, on the one hand, the consistency between the hourly test value VH _C transmitted and the predetermined time range PH, and on the other hand, the consistency between VH _C and the hourly control value VH _S memorized in the lock.

For example, in the case of a time slot reduced to an interval [VH1, VH2], it is verified that VH _C is posterior to VHl and prior to VH2, and that VH _C is posterior to VH _S.

If one of the verifications carried out in steps 1005 and 1006 gives rise to a negative response, the access of this key to this lock is prohibited.

If all of these checks have been satisfied, access is authorized and VH _{S is} updated by replacing it, for example, with the hourly test value VH _C.

Another embodiment of the method of the invention is described below, which provides increased security compared to the previous embodiment. We consider an accessed resource that is not self-sufficient in energy and / or that has only a limited potential for verifying an access right.

By "right of access" is meant the electronic signature of a range of validity. An electronic signature can be obtained using various cryptographic mechanisms, such as encryption mechanisms, or authentication. It can for example be obtained using a secret key signature algorithm or a public key signature algorithm. When a "accessing resource", or "electronic key", presents a right of access to a "accessed resource", or "electronic lock", a protocol verification of the right of access is implemented. In this embodiment, this protocol includes, in addition to checking the range of validity, checking the electronic signature of this range of validity. In this embodiment, the validity range can be either the period proper during which it is possible to access the resource, or the period of validity of a signature key of the accessing resource allowing it to authenticate vis-à-vis the accessed resource, or any other parameter making it possible to limit in time an attack by fraudulent use of the accessing resource.

As shown in FIG. 2, in this embodiment, a first step 2001 consists, as in step 1001 in the previous embodiment, in storing in the electronic lock a control hourly value VH _S , issued by the validation entity.

In the case where the electronic signature S used is calculated using a public key algorithm, of the RSA (Rivest Shamir Adleman) type for example, the public key K _P for verifying the signature is stored in the electronic lock . This public verification key K _p must be stored so that it cannot be modified by an unauthorized entity. The key K _p will if necessary be stored in a physically protected memory.

The electronic signature S can also be calculated using a secret key algorithm, of the DES (Data Encryption Standard) type for example. In this case, unlike the previous case, the verification key which is stored in the lock in step 2001 is secret. Therefore, it will have to be stored in a memory physically protected, so that it cannot be read or modified by an unauthorized entity.

We then consider a situation where the electronic key attempts to access the electronic lock. As in the previous embodiment, a protocol for verifying the right of access of this key to this lock is implemented successively in the key and in the lock.

In the key, as indicated in 2002 in FIG. 2, one reads or establishes an electronic signature S (PH) of the predetermined time slot PH. This step takes place, either in addition to or in place of step 1002 of reading the time slot PH of the previous embodiment.

This electronic signature S (PH) may have been calculated beforehand, for example by an external entity for calculating signatures, independent of the key.

In this case, during a loading step, for example by means of a validation terminal, the aforementioned validation entity transfers and stores the signature S (PH) in the key before this key is put into service.

As a variant, the key can itself establish the signature, if the private key necessary for this operation, as well as the cryptographic signature algorithm, has been stored in the electronic key, and if this key has the necessary computing resources.

As indicated in 2003, during the access attempt, the test hourly value VH _C delivered by the validation entity is stored in the key.

Then, in 2004, the electronic signature S (PH) of the validity range and the hourly test value VH _C are transmitted to the lock. If, in step 2002, the time range PH was read in addition to the signature S (PH), we transmit also this time slot PH at the lock in step 2004.

The following verification steps then take place in the lock. In 2005, we verify the signature transmitted. If the signature calculation algorithm is a public key algorithm, step 2005 consists, for the electronic lock, of applying the public key K _P , previously stored in the lock, to the verification algorithm. The positive verification of the signature makes it possible to ensure the authenticity of the range of validity [VH1, VH2], said range being obtained either by re-establishing the message during the signature verification stage, or by simple reading if it was transmitted in clear with the signature.

In 2006 and 2007, we check, on the one hand, the consistency between the hourly test value VH _C transmitted and the predetermined time range PH, and on the other hand, the consistency between VH _C and the hourly control value VH _S memorized in the lock.

If one of the verifications carried out in steps 2005, 2006 and 2007 gives rise to a negative response, the access of this key to this lock is prohibited.

If all of these checks have been satisfied, access is authorized and VH _{S is} updated by replacing it, for example, with the hourly test value VH _C. A third embodiment of the method of the invention is described below with the aid of FIG. 3, which is likely to provide increased security compared to previous embodiments.

The steps 3001 and 3002 illustrated in FIG. 3 are respectively identical to the steps 2001 and 2002 of the previous embodiment and will not be described again.

As indicated in 3003 in FIG. 3, during the access attempt, the test hourly value VH _C delivered by the validation entity is stored in the key. In addition, an electronic signature S (VH _C ) of the hourly test value VH _C received from the validation entity is calculated and stored in the key.

As a variant, this electronic signature S (VH _C ) can be calculated by a signature calculation unit independent of the key, for example contained in the validation entity.

In this case, upon delivery of the hourly test value VH _C , the validation entity also transfers and stores the signature S (VH _C ) in the key. As a variant, the key can itself establish the signature of the test value VH _C , if the private key necessary for this operation, as well as the cryptographic signature algorithm, has been stored in the electronic key, and if this key has the necessary computing resources. Then is transmitted to the lock, in 3004, the electronic signatures S (PH) of the PH validity range and S (VH _C) of the hourly value VH _C test, and the value VH _C Test schedule. If, in step 3002, the time range PH has been read in addition to the signature S (PH), this time range PH is also transmitted to the lock in step 3004.

The following verification steps then take place in the lock. In 3005, the signatures S (PH) and S (VH _C ) transmitted are verified, for example by means of the same verification algorithm. If the signature calculation algorithm is a public key algorithm, step 3005 consists, for the electronic lock, of applying the public key K _P , previously stored in the lock, to the verification algorithm.

The positive verification of the signature S (PH) makes it possible to ensure the authenticity of the range of validity [VH1, VH2], this range being obtained, either by restoring the message during the stage of verification of signature, or by simple reading if it was transmitted in clear with the signature.

The positive verification of the signature S (VH _C ) ensures the authenticity of the hourly test value VH _C.

The following steps 3006 and 3007 are respectively identical to the steps 2006 and 2007 of the previous embodiment and will not be described again.

If one of the verifications carried out in steps 3005, 3006 and 3007 gives rise to a negative response, the access of this key to this lock is prohibited.

If all of these verifications have been satisfied, access is authorized, and VH _{S is} updated by replacing it, for example, with the hourly test value VH _C , as in the previous embodiments.

A particular embodiment of the access control system according to the present invention will now be described with the aid of FIG. 4.

The system includes an electronic key 1 and an electronic lock 2.

The electronic key 1 comprises a memory 13, in which the validity range PH is stored and a hourly test value VH _C , such as that delivered by the external validation entity (not shown in FIG. 4) as part of the access control method described above. The memory 13 is connected to a module 14 for communication of the key with the lock. The module 14 allows the key, during each access attempt, to transmit to a communication module 21 included in the lock 2 the time range PH as well as the test time value VH _C delivered by the validation entity , the values PH and VH _C being stored in memory 13.

The module 21 for communicating the lock with the key is connected to a memory 22 which can be read and written, in which a hourly control value VH _S is stored, such as that delivered by the external validation entity in the context the access control method described above.

The control hourly value VH _S is updated, for example using the test hourly value VH _C transmitted by the key 1, on each successful access attempt. The memory 22 is for example an electrically reprogrammable memory of the EPRO or EEPROM type.

The electronic key 1 can, by way of nonlimiting example, be produced in a form analogous to that of an assembly described in relation to FIG. 7 of this application. The content of the aforementioned application No. 98 10396 is incorporated by reference in the present description. As shown in Figure 7 of the present application, the electronic key 1 includes a transmission module - receiving 1 ₂ control signals key access. This module 1 ₂ can advantageously comprise a module for transmitting the key access control signals and a module for receiving the lock access control signals. By convention, the key access control signals designate the access control signals emitted by the key towards the lock and the lock access control signals designate the access control signals emitted by the lock towards the key.

The electronic key 1 also comprises, as indicated above, a calculation unit, called the logical key calculation unit l _x . The logical key calculation unit li makes it possible to control all of the operating operations of the electronic key 1.

The electronic lock 2 also comprises, as indicated above, a calculation unit, called the logical lock calculation unit 2ι, and a transmission / reception module 2 ₂ of lock access control signals.

Conventionally, the logic unit for calculating the lock 2 _X also makes it possible to control all of the operating operations of the electronic lock 2. Thus, under the respective control of the logic units for calculating the key and the lock l _x and 2ι, the transmission - reception modules for key and lock access control signals 1 ₂ and 2 ₂ allow the implementation of an access control protocol between the electronic key 1 and the electronic lock 2 .

The assembly shown in Figure 7 of this application further comprises, at the electronic key 1, a module 1 ₃ generator of a power signal.

The power module 1 ₃ can be supplied by an external electrical energy source (not shown). As a variant, but not necessarily, the power module 1 ₃ can be powered by an optional power supply module. energy 11, shown in Figures 4, 5 and 6 of this application, by way of non-limiting example.

The power module 1 ₃ can be controlled by the logical key calculation unit lχ. Thus, all of the functional modules for transmitting - receiving 1 ₂ of key access control signals and power generator 1 ₃ are connected by a link to the logical key calculation unit l _x and controlled by this last. In addition, as shown in Figure 7, the electronic key 1 comprises a first transfer circuit called key transfer circuit 1 ₄ , allowing in particular the transfer of key access control signals and lock as well as the signal power generated by the power module 1 ₃ . More specifically, the key transfer circuit 1 ₄ is connected, on the one hand, to the power module 1 ₃ and on the other hand, to the module for transmitting reception of key access control signals 1 ₂ .

As shown in Figure 7, the electronic lock 2 has a second transfer circuit, said lock transfer circuit 2 ₄ allowing in particular the transfer of key and lock access control signals and the power signal mentioned above.

In addition, the electronic lock 2 also includes a module 2 ₅ for ensuring the storage and therefore the recovery of the electrical energy conveyed by the power signal.

As shown in a nonlimiting manner in FIG. 7, the lock 2 can also be provided with a module 2 ₃ for recovering a clock signal.

The functional modules constituting the electronic lock 2, that is to say, in the particular mode of embodiment of FIG. 7, the transmission module - reception of the lock access control signals 2 ₂ , the electrical energy storage module 2 ₅ and, if necessary, the clock recovery module 2 ₃ , are connected via a link to the logic unit for calculating lock 2.

The lock transfer circuit 2 ₄ is connected, on the one hand, to the transmission - reception module 2 ₂ of the lock access control signals and, on the other hand, to the energy storage module 2 ₅ as well as, if necessary, to the clock recovery module 2 ₃ .

Advantageously without limitation, as shown in Figure 7, the transfer circuit 1 of the key and the transfer circuit 2 ₄ of the lock can be constituted by the primary winding and the secondary winding of a transformer . In such conditions, the primary windings, denoted Li, and secondary, denoted L ₂ , are coupled from the electromagnetic point of view when the electronic key and the electronic lock are brought into contact, this contacting being carried out for make an access attempt.

As shown in FIG. 4, the lock 2 further comprises a comparison module 25, which receives the hourly test value VH _C transmitted by the key 1, and compares it with the predefined time range PH = [VH1, VH2] and at the hourly control value VH _S stored in memory 22. The comparison module 25 tests if VH _C > VH1 and VH _C <VH2, and if VH _C > VH _S.

In a particular embodiment, as indicated above, the key 1 may further comprise a power supply module 11 for supplying the lock 2 with the energy necessary for verification operations performed by the comparison module 25, as well as the energy necessary for the operation of updating the hourly control value VH _S stored in the memory 22 in the event of a successful access attempt. As a variant, the key 1 does not include any energy supply module and the energy necessary for the verification and updating operations is supplied by an external electrical energy source.

With the aid of FIG. 5, another embodiment of the access control system of the invention is described below, comprising an electronic key 41 and an electronic lock 42, which provides increased security with respect to in the embodiment of FIG. 4.

The elements of this system which are analogous to those of the embodiment of FIG. 4 bear the same reference numbers, and will not be described again.

In this embodiment, the memory 13 of the key 41 contains not only the range of validity PH, but also the electronic signature S (PH) of this range of validity.

The module 14 for communication of the key with the lock allows the key 41, during each access attempt, to transmit to the communication module 21 included in the lock 42, not only the hourly test value VH _C and the time slot PH, stored in memory 13, but also the electronic signature S (PH) stored in memory 13.

The lock 42 comprises, in addition to the module 21 for communication with the key, the memory 22 and the comparison module 25, described above, a signature verification module 24. The module 24 is connected to the module 21 for communication of the lock with the key and to the comparison module 25. The module 24 receives the signature S (PH) of the validity range and, in the case where the signature calculation algorithm used is a public key algorithm, verifies the signature S (PH) received by means of the public key K _P.

As previously, in a particular embodiment, the key 41 may further comprise a power supply module 11, for supplying the lock 42 with the energy necessary for the verification operations performed by the verification module 24. signature and the comparison module 25, as well as the energy necessary for the operation of updating the hourly control value VH _S stored in the memory 22 in the event of a successful access attempt.

As a variant, the key 41 does not include any energy supply module and the energy necessary for the verification and updating operations is supplied by an external electrical energy source. A third embodiment of the access control system of the invention is described below, with the aid of FIG. 6, also comprising an electronic key 41 and an electronic lock 42, which is capable of providing a increased security compared to previous embodiments.

The elements of this system which are analogous to those of the embodiment of FIG. 5 bear the same reference numbers, and will not be described further.

In this embodiment, the memory 13 of the key 41 contains not only the range of validity PH and the electronic signature S (PH) of this range of validity, but also the electronic signature S (VH _C ) of the hourly test value.

The module 14 for communication of the key with the lock allows the key 41, during each access attempt, to transmit to the communication module 21 included in the lock 42, not only the hourly test value VH _C , the time slot PH and the electronic signature S (PH), stored in memory 13, but also the electronic signature S (VH _C ) stored in memory 13.

The signature verification module 24 receives the signatures S (PH) of the validity range and S (VH _C ) of the test value, in the case where the signature calculation algorithm used is a public key algorithm , verifies these signatures using the public key K _P.

As previously, in a particular embodiment, the key 41 may further comprise a power supply module 11, for supplying the lock 42 with the energy necessary for the verification operations performed by the verification module 24. signature and the comparison module 25, as well as the energy necessary for the operation of updating the hourly control value VH _S stored in the memory 22 in the event of a successful access attempt. As a variant, the key 41 does not include any energy supply module and the energy necessary for the verification and updating operations is supplied by an external electrical energy source.

FIG. 8 illustrates a particular hardware embodiment of the modules 14 and 21 for communication between the key and the lock, applicable both to the mode of embodiment of FIG. 4 than in the embodiments of FIGS. 5 and 6.

The key 1 (or 41 in the case of the embodiments of FIGS. 5 and 6) comprises a rod 30 made of ferromagnetic material, furnished with copper windings 31 forming a first winding. This first winding is connected to the module

14 for communication of the key with the lock.

At each access attempt, the key 1 or 41 is housed in a tubular cavity 32 with a diameter slightly greater than the diameter of the rod 30. The cavity 32 is also furnished with copper windings 33 forming a second winding, connected to the module 21 for communication of the lock with the key. The two windings 31, 33 are then concentric, and the information is transmitted in binary coded form between the key and the lock 2 (or 42 in the case of the embodiment of FIG. 5) by electromagnetic induction.

The present invention finds an application particularly suitable for access, by successive users, to resources which are only made accessible to a given user after having been released by a previous user, and which, after the access achieved by this given user no longer allows access to the previous user. It is thus possible to apply the invention to resources such as hotel rooms or lockers with automatic deposit.

The security of the access control can be further strengthened by adding other data to the signature and time slot information transmitted by the key to the lock. For example, you can add a serial number identifying the electronic key. In this case, the lock can be fitted with a counting module, associated with this serial number. The beginning of the next time slot during which a key bearing this serial number can access the lock is memorized in this counting module.

Claims

1. Method for controlling access of at least one electronic key to at least one electronic lock, within a predetermined time range, according to which:

(a) prior to any attempt to access the electronic key to an electronic lock, a control hourly value (VH _S ) is stored in the lock, delivered by a real time clock from an external validation entity; then, during each attempt to access the electronic key to an electronic lock: in the electronic key: (b) a predetermined time slot (PH) is read, previously stored in the electronic key;

(c) storing in the key a test hourly value (VH _C ), delivered by the real time clock of said external validation entity; (d) the time range (PH) and the test time value (VH _C ) are transmitted from the electronic key to the electronic lock, and in the electronic lock:

(e) it is verified that the transmitted hourly test value (VH _C ) is within the predetermined time range (PH), and that it is later than the control hourly value (VH _S ) stored in the lock ;

(f) if the verifications carried out in step (e) are satisfied, access is authorized, and the hourly control value (VH _S ) is updated, from the hourly test value (VH _C ) transmitted; (g) if the transmitted hourly test value (VH _C ) is outside the predetermined time range (PH), or if it is earlier than the control hourly value (VH _S ) stored in the lock, prohibits access of this key to this lock.

2. Method according to claim 1, characterized in that: in the electronic key:

(bl) in step (b), we read, in addition to the time slot (PH), or instead of the time slot (PH), an electronic signature (S (PH)) of said time slot

(PH), previously calculated and stored in the electronic key;

(dl) in step (d), the electronic key is transmitted to the electronic lock, on the one hand, said electronic signature (S (PH)) in addition to or instead of the time slot (PH) , and, on the other hand, of said hourly test value (VH _C ), and in the electronic lock: (el) before step (e), the transmitted signature is checked (S (PH)), at from a specific verification key;

(fl) in step (f), access is not authorized, and the control hourly value (VH _S ) is not updated, from the transmitted hourly test value (VH _C ), if the verifications carried out in steps (el) and (e) are satisfied;

(gl) in step (g), access of said key to said lock is prohibited if the hourly test value (VH _C ) transmitted is outside of said time range (PH), or if it is earlier than the hourly control value (VH _S ) stored in the lock, or if the verification carried out in step (el) is not satisfied.

3. Method according to claim 2, characterized in that the order of execution of steps (el) and (e) is reversed.

4. Method according to claim 2 or 3, characterized in that said specific verification key is a public or secret key.

5. Method according to any one of the preceding claims, characterized in that: in the electronic key:

(c2) in step (c), in addition to the hourly test value (VH _C ), a electronic signature (S (VH _C )) of this hourly test value is calculated and stored; (d2) in step (dl), said electronic signature (S (VH _C )) of the hourly test value (VH _C ) is further transmitted from the electronic key to the electronic lock. electronic lock:

(e2) before or after step (e), the signature (S (VH _C )) of the test value is verified, using a second specific public or secret verification key;

(f2) in step (f), access is authorized, and the control hourly value (VH _S ) is only updated, if the checks carried out in steps (e), (el) and (e2) are satisfied;

(g2) in step (g), access of said key to said lock is prohibited if one of the verifications carried out in steps (e), (el) or (e2) is not satisfied.

6. Method according to any one of the preceding claims, characterized in that said predetermined time slot comprises several disjoint time slots.

7. Method according to any one of the preceding claims, characterized in that each time slot is an interval comprising two limits each expressed as a date in day, month, year and a schedule in hours, minutes, seconds.

8. Electronic access control system, within a predetermined time range, comprising at least one electronic lock (2; 42) and at least one electronic key (1; 41), characterized in that the key (1; 41) includes:

means (13) for storing a test hourly value (VH _C ), accessible in reading and writing, and

- communication means (14) for transmitting to the lock (2; 42) a predetermined time slot (PH) and said test hourly value (VH _C ), and in that the lock (2; 42) comprises:

means (22) for storing a control hourly value (VH _Ξ ), accessible in reading and writing, and

- Means (25) for comparing the hourly test value (VH _C ) with the predetermined time range (PH) and with the hourly control value (VH _S ) stored in said means (22) for memorizing the lock .

9. System according to claim 8, characterized in that said means (14) of communication of the electronic key (1; 41) further comprise means for transmitting to the lock (2; 42) an electronic signature (S (PH )) of said time slot (PH) and an electronic signature (S (VH _C )) of said test hourly value

(VH _C ) t and in that the lock (2; 42) further comprises means (24) for verifying the electronic signatures (S (PH), S (VH _C )) transmitted by the key (1; 41).

10. System according to claim 8 or 9, characterized in that said storage means (22) comprise an electrically reprogrammable non-volatile memory.

11. System according to claim 8, 9 or 10, characterized in that the electronic key (1; 41) communicates with the electronic lock (2; 42) using contactless transmission means, by electromagnetic induction.

12. System according to claim 11, characterized in that said contactless transmission means comprise a first electromagnetic coil (31) provided in the key (1; 41) and a second electromagnetic coil (33) provided in the lock (2; 42).

13. System according to claim 12, characterized in that the coils (31,33) provided in the key (1; 41) and in the lock (2; 42) are concentric.

14. In an electronic access control system within a predetermined time range comprising at least one electronic key and an electronic lock according to one of claims 8 to 13, an electronic key (1; 41) comprising at least one logical key calculation unit (li), a module (1 ₂ ) for transmitting - receiving key access control signals for implementing an access control method between this key electronic (1; 41) and an electronic lock (2; 42) from lock access control signals generated by this electronic lock (2; 42), characterized in that this electronic key further comprises: means (1 ₃ ) generating a power signal, controlled by said key calculation unit (lχ); and

- key transfer means of said key and lock access control signals and of said power signal, said key transfer means comprising at least one winding (Li) interconnected with said means (1 ₃ ) generating a power signal and said transmission (reception) module (1 ₂ ).

15. In an electronic access control system within a predetermined time range comprising at least one electronic key and an electronic lock according to one of claims 8 to 13, an electronic lock

(2; 42) comprising at least one logical unit for calculating a lock (2χ) and a module (2 ₂ ) for transmitting - receiving lock access control signals for implementing a control method of access between this electronic lock (2; 42) and an electronic key (1; 41) from key access control signals and a power signal generated by this electronic key, characterized in that this electronic lock also includes:

- lock transfer means of said key and lock access control signals and of said power signal, said lock transfer means comprising at least one winding (L ₂ ) interconnected with said transmission module (2 ₂ ) - reception of lock access control signals; and means ( ₂₅ ) for storing the electrical energy conveyed by said power signal, interconnected with said winding (L ₂ ).