AU724882B2

AU724882B2 - Secured access checking system enabling the automatic disabling of stolen or lost electronic keys and/or the transfer of entitlement to produce keys

Info

Publication number: AU724882B2
Application number: AU26433/97A
Authority: AU
Inventors: Marc Girault; Didier Guerin; Constant Hardy; Marie-Josephe Revillet
Original assignee: POSTE
Current assignee: LA POSTE
Priority date: 1996-04-19
Filing date: 1997-04-15
Publication date: 2000-10-05
Anticipated expiration: 2017-04-15
Also published as: CA2252001A1; EP0956540A1; FR2747813A1; WO1997040473A1; AU2643397A; JP2000509451A; FR2747813B1

Description

012989 SECURED ACCESS CHECKING SYSTEM ENABLING THE AUTOMATIC DISABLING OF STOLEN OR LOST ELECTRONIC KEYS AND/OR THE TRANSFER OF ENTITLEMENT TO PRODUCE KEYS The present invention relates to a secured system of access checking that enables the automatic disabling of stolen or lost logic keys and/or the transfer of entitlement to produce keys.

The invention can be applied especially in the field of the checking of accE buildings, computer systems or any kind of object for which the opening or use has to be checked.

There is the known patent application PCT/FR95/00935 published under number W096/029899, for an access checking system limited to authorized and renewable time slots.

This system relies on the use of portable storage carriers such as chip cards (integrated circuit cards) with flush contacts or without contact, magnetic cards, badges and electronic keys with or without contact.

These carriers are distributed to all users to whom access is to be authorized.

For this purpose, the magnetic carriers have a memorized electronic key giving a right of access.

This key has a data element corresponding to an access authorization period and a digital signature of this data element. The period of use corresponds in practice to a date of use and to a time slot of use so much so that the key is valid only for one day and for the specified time slot.

These keys have a short lifetime and are especially well suited to applications such as the distribution and collection of mail by a postman. The user of such a -2carrier must recharge his carrier every day with a new valid key.

The problem of the theft and loss of an information carrier comprising a key of this kind no longer arises since the lifetime of the logic key is ephemeral.

Anyone who has found or stolen the carrier will no longer be able to use it the next day. Consequently, it is no longer even necessary to keep a black list of all the carriers that have been stolen or lost.

This access checking system is highly efficient in applications where no permanent access right or very long-term access right has to be provided. However, if this is not the case, the system proves to be unsuitable.

Earlier checking systems propose the keeping of a black list for stolen or lost carriers in order to prevent unauthorized holders of such carriers from accessing the protected unit.

The maintaining of such lists requires action on electronic locks. For it is ••necessary to make recordings, on these locks, of the identification numbers of the carriers •.ooo* Is that are stolen or lost after their holder has reported the loss. Such action entails

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a constraints.

It is an object of the present invention to substantially overcome or at least O.0.

ameliorate one or more deficiencies of existing arrangements.

The secured access checking system proposed enables the automatic disabling of

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20 keys reported to be lost or stolen.

S* Indeed, according to the present invention, there is no particular action to be taken on electronic locks. It is the carriers of the users that will enable the lost or stolen carriers to be disabled automatically.

[R:\LIBQ]00403.doc:bfd -3- Furthermore, should a person who is entitled to produce electronic keys and record them on the storage carriers have his entitlement withdrawn (in the case of rights of access to a building, this could be for example because of a change in the managing agent or manager of the building), the transfer of entitlement to another person makes it necessary to provide all users who had access rights with new carriers on which the electronic keys are computed with the key-producing means possessing the new entitlement.

This is a constraint that leads to substantial costs.

The secured access checking system according to the invention can be used to i0 substantially overcome or at least ameliorate this problem too. The carriers delivered remain always valid even in the event of a transfer of entitlement to another person or more specifically to another key-producing means.

According to an aspect of the present invention, there is provided a system of access checking by means of a portable storage carrier on which there is recorded an electronic key (CL) including a first data element for the identification of the user and a S. means fulfilling an electronic lock function capable of authorizing access should the storage carrier contain the requisite electronic key, wherein: 1* ~the electronic key CL further comprises a second data element DpA specific to

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the carrier and the digital signature S of the data elements, 20 these data elements are recorded in the lock at the first use of the carrier, S" a new electronic key CL' is produced and this key is recorded on another storage carrier for this same user in the event of loss or theft of the previous carrier, with a new specific data element DpA' having a value higher than the previous specific data element [R:\LIBQ]00403.doc:bfd -4- DpA and invalidating the previous specific data element DpA, at each use of the carrier, the lock verifies the digital signature S and ascertains that the specific data element DPA of the key CL of the carrier is equal to or greater than the data element already recorded and permits access only when these conditions are met.

According to a preferred feature, the signature S is computed from an algorithm with a secret key k and a corresponding public key K by production means LE, and the lock has, in memory, the public key K, a function VK for the verification of this signature S and a means to implement this verification function.

According to another preferred feature, in order to verify a data element DpA specific to a user, the lock: compares the specific data element DPA that is present on the carrier with the data element already recorded during the first use for this user, and

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records this data element instead of the data element already recorded when its C. CCo Is value is greater than the data element already recorded.

:o The data element DPA specific to a user may be the date of customization of his storage carrier.

The specific data element D A may be a value obtained by a counter, this value •.being incremented at each new version of a key for a given user.

i 20 These operations enable the automatic updating of the issuance of a new carrier to a user by the recording, in the lock, of the new data element specific to the carrier, replacing the previous one.

When a new carrier is customized for a given user, the specific data element DPA (the date of customization) has a value greater than the previous one.

[R:\LIBQ]00403.doc:bfd The electronic key CL recorded in a carrier also has a data element identifying this carrier. For example it will be the serial number of manufacture of the carrier.

To increase security, the electronic lock has a data element corresponding to a reference value DH. Access authorization is given only if, in addition, thedata element DpA specific to the user has a value smaller than the reference value DH.

The reference data element DH may be the current date given by an internal clock of the electronic lock.

According to another preferred feature of the present invention, the production means comprise an entitlement information element HA given by an authority to produce the keys CL, including a public key K, and the digital signature CER of this information element; and a transfer of entitlement to new production means is made by the recording of a new public key K' and the corresponding signature CER'.

o The lock verifies any new entitlement.

~To this end, any new public key is recorded in the electronic lock for verification o. *o.

is with its certificate which, in principle, will not be kept.

According to another preferred feature, the data elements pertaining to the i production means comprise an identification data element ID, a period of validity VAL and the public key K, the period of validity assigned to the former key K having an ending date that corresponds to the starting date of validity of the period of validity of the i 20 new key this ending date possibly being later than the starting date (for example later by one month).

[R:\LIBQ]00403.doc:bfd -6- According to another preferred feature, for the verification of a new version of a key K' with a signature CER', the lock compares and replaces the ending date of the period of validity of the former key by the starting date of validity of the next key.

Advantageously, during a verification of an electronic key, the lock furthermore performs the following steps: comparing the customization date DpA with the period of validity VAL of the public key K that has been used, authorizing access if this date should be within the period of validity of this key, and, if not, refusing access.

The public keys K, K' are obtained by the authority through a production function FKA with public key KA, using a secret key ka. The lock has, in memory, at the time of verification, a verification function VKA and the key KA for the verification of the °signatures CER or CER'.

A further aspect of the present invention is a system for access checking by oo* S 15 means of a portable storage carrier C on which there is recorded an electronic key CL, means for the production of these electronic keys and a means carrying out an electronic key function L capable of authorizing access if the storage carrier should have the requisite electronic key, according to which the production means comprise an oo.

information element HA for entitlement to produce the keys CL, including a public key oooo K, and the digital signature CER of this information element, and in which a transfer of entitlement to new production means is made by the recording of a new public key K' and the corresponding signature CER'. This new public key is, after [R:\LIBQ]00403.doc:bfd verification of the entitlement, recorded in the electronic lock L which verifies the keys CL produced by the means LE.

According to another preferred feature, the data elements pertaining to the production means comprise an identification data element ID, a period of validity VAL and the public key K. The period of validity assigned to a new key K' has a starting date that corresponds to the ending date of validity of the period of validity of the previous key K.

Advantageously, for the verification of a new version of the public key with a signature CER', the lock compares the starting date of the period of validity of the new key with the date of the end of validity of the previous key.

The public keys are obtained by the authority by means of a production function FKA with a public key KA, using a secret key ka, the lock having, in memory, at the time of verification, a verification function 20 VKA and the key KA for the verification of these go ooo signatures CER or CER' Thus, when a new production means is in service, "this means is declared to the lock that will check the keys produced by this means.

For this purpose, the authority records the :eo: entitlement certificate in the lock and the key KA that S'-it has used for the computation. The production means may itself record its entitlement in the lock.

The carriers whose keys have been produced 30 fraudulently by means that no longer have entitlement do not permit access to the units protected.

Indeed, the transfer of entitlement is done by the secured loading of a new public key into the lock.

8 The previous public keys are in principle preserved unless the production algorithm has been broken or the secret key of the pair formed by the secret key and the public key has been discovered.

Other advantages and features of the invention shall appear from the following description given by way of a non-exhaustive indication with reference to the appended drawings, of which: Figure 1 shows a secured access checking system according to a first object of the invention, Figure 2 shows a secured access checking system according to a second object of the invention.

It is specified that the term authority is understood to mean an organization possessing secret keys, means capable of delivering public keys and entitlement data elements.

The term secret key is understood to mean a digital data element that is known only by a unit of the authority or by a production means.

S20 The term public key KA, K, is understood o o o :r to mean a digital data element shared among several users, the authority and the means of production of the electronic keys or the means of production and the electronic lock.

The term production means LE of keys is .understood to mean a digital data processing *instrument, for example a microcomputer, containing an entitlement information HA and having computation means ••go to obtain the digital data signal implementing functions such as an algorithm with a conventional S• public key.

The term electronic key or logic key CL is understood to mean a one or more digital data elements accompanied by their digital signature giving right to access.

The invention is described by way of an example in its application to the management of access to buildings.

Reference may be made to the diagram of Figure 1 for a clearer understanding.

The storage carriers C comprising the electronic keys distributed to authorized users could be either chip cards or chip keys or badges or magnetic cards.

The transmission between the carrier C and the lock L may be done through electronic contacts or by radioelectric means or by the reading of a magnetic tape.

By way of an example, a chip card has been chosen as a carrier.

It has an input/output interface I/O 100 and an electrically recordable non-volatile memory 101.

In the example described, the customization of a carrier C consists especially of the recording, in the memory, of an information element IDA for the identification of the user A comprising for example, his name, the number of his apartment and the specific data element D pA that is assigned to him. In a preferred exemplary embodiment, this data element DpA is the date of customization of his storage carrier.

A recording is also made in the memory of an information element identifying the carrier. It is for example the serial number NS of manufacture of the carrier. In general, this information element is entered at the end of manufacture, before the carrier is handed over to the authority AT.

The customization of the carriers is done by the instrument LE (and the person who uses it) possessing an entitlement HA (ID, KA, CER, K).

The production machine LE is for example formed by a PC type microcomputer provided with a card reader.

The diagram of Figure 1 gives a schematic view of the different functional blocks of this instrument LE.

The production machine LE has a microprocessor type processing unit 200 connected by a bus 201 to memories.

A RAM type volatile working memory 202 contains the data elements of the application.

An EEPROM type non-volatile memory has, in a protected zone, the secret key k used for the production of the electronic keys. It furthermore has the program for the production of electronic keys. This program implements a production algorithm of the type with public key FK using the secret key k and the corresponding public key K.

The memory 203 furthermore comprises the customization program which consists of the writing of the characteristic data element, namely according to the preferred embodiment, the date DpA of the day of customization (plus the time as the case may be). This information is obtained from an internal clock 204.

The specific data element may also be obtained by a counter 206 whose value is increased (incremented by 1 for example) with each new version of a key.

The performance of these programs is launched by the entitled person by means of the keyboard 205.

According to another aspect of the invention, the volatile memory 203 may also contain the public key KA and the entitlement certificate CER.

Indeed, a production machine LE must be entitled to produce keys CL. The entitlement, for its part, is taken up again by the authority AT.

In practice, the authority gives it a public key K which will be used by it in the computation of the keys CL. However, the key K is transmitted to it with a signature that is herein called the certificate CER.

This certificate CER is therefore the digital signature of a set of data elements including the identity of the authorized person ID, his public key K and the period of validity VAL such that: CER FKA (ID, VAL, K), FKA being the public key algorithm, ka being the secret key for the computation of the certificate and KA being the corresponding public key. This computation is done by the authority AT.

The electronic locks CL are formed by a chip card reader or microcomputer type of machine fitted out with a chip card reader interface for the exemplary embodiment described.

The lock L has a processing unit 300, an electrically programmable non-volatile memory 301 and a working memory 302. The memory 301 has a program for the verification of the keys implementing a function VK for the verification of the electronic keys CL.

This memory 301 also contains the public key K corresponding to the secret key k that has been used for the production of the keys CL.

The lock L, according to a first object of the invention, enables the detection of false electronic keys.

For this purpose, the lock compares the customization date D pA of the key CL with the customization date that it has memorized for the same carrier (IDA identification) If there is equality, the lock permits access. If the date DpA the date of customization present in the lock, then it is a case of a new version of key. The lock updates its list of keys, namely it registers the new date of customization instead of the old one.

If the date DpA the customization date present in the lock, then it is a case of a re-utilization of a key that has been reported to be stolen or lost.

Access is prohibited. There is no updating of the list of keys.

When an entitlement HA is assigned, the pair consisting of the public key and certificate CER of the key-production machine LE as well as the key KA are recorded in the lock in a working memory for example to enable the lock to perform a verification of entitlement.

This verification is done at each new entitlement.

For this purpose, the key contains also the program of verification of the certificate, and this program implements a function of verification VKA of the certificate. At the end of this verification, if the certificate truly corresponds to the public key K, the key is recorded in an EEPROM memory, and the certificate and the key KA are not preserved.

When a change in entitlement takes place, a certificate CER' for a new key K' is computed by the authority AT and loaded into the instrument LE.

Reference may be made, for the rest of the description, to the drawing of Figure 2.

Thus, according to a second object of the invention, this change in entitlement consists of the use of a new public key K' and of the assigning of this new key K' to the machine.

Electronic keys CL computed by the instrument that had the former public key K will be always valid as well as the new keys that are produced by an instrument having the key provided that the lock has verified this new entitlement.

The period of validity assigned to the key K is chosen so that it has an ending date of validity equal to the starting date of the period of validity assigned to the key K' or a date that is slightly later (by one month for example).

Should a production machine LE have a data element on entitlement HA (ID, KA, CER, be it a first entitlement or a new entitlement, and should the keys produced CL DpA, IDA) have a specific data element such as the date of customization of the carrier on which they are recorded, the lock could verify the conditions of access stipulated in the first part of the description and furthermore compare the date DpA with the period of validity of the public key of the instrument.

This comparison will make it possible for example to detect the keys CL that might have been produced when the production machine LE no longer had any entitlement.

Indeed, the customization dates DpA obligatorily fall in one or the other of the periods of validity VAL or VAL' of the keys K or K'.

In each case, the lock could then compare the customization date with the corresponding period of validity of the corresponding public key. The lock authorizes access when, at the end of this 14 verification, it finds that the date DpA is within the period of validity of the corresponding public key.

Since each public key K or K' has a period of validity that is specific to it, it is easy to detect fraud.

Claims

1. System of access checking by means of a portable storage carrier on which there is recorded an electronic key CL including a first data element for the identification of the user, and a means fulfilling an electronic lock function capable of authorizing access should the storage carrier contain the requisite electronic key, wherein: the electronic key CL further comprises a second data element DpA specific to the carrier, and the digital signature S of these data elements, these data elements are recorded in the lock at the first use of the carrier, a new electronic key CL' is produced and this key is recorded on a new storage carrier for this same user in the event of loss or theft of the previous carrier, with a new specific data element DpA' having a value higher than the previous specific data element DpA and invalidating the previous specific data element DPA, at each use of the carrier, the lock verifies the digital signature S and 15 ascertains that the specific data element DpA of the key CL of the carrier is equal to or -:greater than the data element already recorded and permits access only when these woo. :conditions are met.

02. Access checking system according to claim 1, wherein the signature S is computed from an algorithm with a secret key k and a corresponding public key K by production means LE, and in that the lock has, in memory, the public key K, a function (VK) for the verification of this signature S and means to implement this verification function. B.

3. Access checking system according to claim 1 or 2, wherein to verify a data element DPA specific to a user, the lock: compares the specific data element DpA that is present on the carrier with the data element already recorded during the first use for this user, and [R:\LIBQ1]28 l.doc:mxl -16- records this data element in place of the data element already recorded when its value is greater than the data element already recorded.

4. Access checking system according to any of the foregoing claims, s wherein the specific data element (DpA) assigned to the carrier of a user A is the date of customization of his storage carrier.

Access checking system according to any of the foregoing claims, wherein the specific data element DpA is a value obtained by a counter, this value being incremented at each new version of a key for a given user.

6. Access checking system according to any of the foregoing claims, wherein the electronic lock has a reference value (DH) and wherein access authorization is given only if, in addition, the data element DPA specific to a carrier has a o* 15 value smaller than the reference value.

7. Access checking system according to any of the foregoing claims, wherein the reference data element DH is the current date given by an internal clock of the electronic lock.

8. Access checking system according to claim 2, wherein the production means comprise an entitlement information element HA given by an authority to produce oo the keys CL, including an identification element ID, a public key K, a period of validity VAL and the digital signature CER of this key, and in that a transfer of entitlement is made to new production means by the recording of a new public key K' and the corresponding signature CER'.

9. Access checking system according to claim 8, wherein the period of \validity assigned to the former key K has an ending date that corresponds to the starting [R:\LIBQ]28 I.doc:mxl -17- date of the validity of the period of validity of the new key K' or is subsequent to this starting date.

Access checking system according to any one of claims 8 and 9, wherein for the verification of a new version of a key K' with a signature CER', the lock uses a verification function with a public key and, furthermore, the lock compares and replaces the ending date of the period of validity of the former key by the starting date of validity of the next key.

11. Access checking system according to any one of the foregoing claims, wherein during a verification of an electronic key CL, the lock furthermore carries out the following operations: comparing the customization date DpA with the period of validity VAL of the public entitlement key K that has been used, 15 authorizing access if this date should be within the period of validity of this key, and, if not, refusing access.

12. Access checking system according to any one of the foregoing claims, wherein the public keys are obtained by the authority through a production function FKA ooo° 20 with public key KA, the lock comprising, in memory, at the time of the verification of an entitlement, a verification function VKA and the key KA.

13. A system of access checking substantially as herein described with reference to the accompanying drawings. DATED this twenty-fifth Day of July, 2000 LA POSTE Patent Attorneys for the Applicant SSPRUSON FERGUSON [R:\LIBQ]281.doc:mxl.