EP2048631A1 - Authentication method, corresponding portable object and computer program - Google Patents

Abstract

The method involves processing an authentication of a signature of a carrier by considering secret information, and delivering information of positive or negative authentication decision. A value indicating an abnormal situation is written in an incorrect signature indicator e.g. counter, after delivering the information if the decision is negative. A delay is generated before authentication if the indicator contains the value. The value is written by storing context relative information e.g. date and time, and/or identifier of a payment terminal i.e. chip card reader terminal. Independent claims are also included for the following: (1) a computer program product comprising instructions to perform a method for authenticating a portable object carrier (2) a secured portable object comprising authentication units.

Description

1. Field of the invention

The field of the invention is that of secure portable objects, such as microprocessor cards, or smart cards. More specifically, the invention relates to the authentication of carriers, or users, of such portable objects, and the fight against fraud attempts, by malicious people attempting to use a secure portable object which they do not hold.

2. Prior Art

Subsequently, the use of smart cards as payment cards is described. Other applications, such as access to a site or service, are of course also known, and treated in the same way. Similarly, it is understood that the concept of "smart card" can be generalized to other types of portable objects equipped with a secure microprocessor.

Smart cards are known and are currently widely used. When a smart card is used as a payment card, the authorized user (the holder) of the smart card can use it, for example to pay purchases at a merchant or to withdraw a ticket at a vending machine of tickets.

When the smart card is used to perform such an operation, it is generally necessary for the authorized user to slip his smart card into a payment terminal and enter his PIN using a payment terminal keypad.

This PIN is also known as the Cardholder's Personal Identification Number (PIN), also known as PIN (Personal Identification Number) or PIN. The PIN associated with a payment chip card is generally composed of a sequence of at least four digits.

Secret information is also stored (stored) in a memory of the smart card. A verification (mathematical treatment) is performed in the smart card, taking into account (at least) this secret information and the confidential code. Thus, when the code entered on the keyboard (signature) matches the secret information stored in the smart card, the card delivers a positive authentication result and allows, for example, secure electronic transactions.

A problem is that a smart card is vulnerable to attack by a malicious third party (a fraudster) who could, for example after stealing the smart card, try to type in a large number of successive combinations of code to find the PIN code of the card.

Different solutions to this problem have been proposed. The best known is probably the one that uses a counter contained in a memory of the smart card that stores the number of incorrect attempts to enter the PIN for a predetermined period of time. Thus, the use of the smart card is blocked when the number of successive incorrect attempts during this predetermined period of time reaches a predetermined threshold value.

A disadvantage with this solution is that a fraudster can interrupt the power supply of the smart card to cause a reset of the counter and feed the smart card again to make new attempts to find the PIN, And so on.

A complementary or alternative solution to the previous one consists in imposing a predetermined delay time between two attempts to enter a code, when the first attempt is incorrect, in order to slow down the fraudster in his search for the confidential code by successive trials and therefore reduce the likelihood that the PIN will be discovered by a fraudster. It is conceivable, however, that the fraudster accelerates the external clock that drives the smart card to reduce the waiting time between two successive attempts to enter a code.

In the case where the power-up time of the smart card is less than the delay time between two successive attempts to enter a code (when the first attempt is incorrect), the fraudster may also temporarily interrupt the power supply of the smart card after the first attempt and thus reduce the waiting time between two successive attempts to enter a code.

3. Objectives of the invention

The invention particularly aims to overcome these disadvantages of the prior art.

More specifically, an object of the invention is to provide a technique for combating attempts to fraudulently use a smart card, or a similar portable object.

Another object of the invention is to reduce the probability that a possible fraudster discovers the PIN of the smart card by successive tests in a relatively short period of time, regardless of the technical means implemented.

The invention also aims to provide such a technique that is relatively inexpensive, reliable and simple to implement.

4. Presentation of the invention

The invention proposes a new solution that does not have all of these disadvantages of the prior art, in the form of a method for authenticating a carrier of a portable object according to claim 1.

Thus, the invention makes it possible to slow down the attempts of a possible fraudster who intends to successively enter a series of signatures, in order to find the correct signature, making it possible to authenticate a carrier. Indeed, even if the fraudster cut off the power supply of the portable object, the latter has memorized the existence of a possible fraud attempt, and systematically impose a delay, or delay, before allowing a new attempt.

The delay may be a function of context information, such as the date and time and / or an identifier of the terminal used, which are stored in the portable object.

In other words, the invention makes it possible to delay the authentication of a carrier of a portable object when the signature previously issued does not correspond to the secret information associated with the portable object, and thus reduces the probability that a possible fraudster will discover, by successive trials, the secret information stored in the portable object, by increasing the time between two tests, without possibility to circumvent or avoid this delay.

According to a particular aspect of the present invention, the method comprises, after said step of generating a delay or after said step of issuing, a step of writing, in said erroneous signature indicator, said value indicating a normal situation.

Thus, the invention makes it possible to deter fraudsters, without introducing too much discomfort for the authorized user, who would have simply made an entry error.

According to a particular embodiment of the invention, said erroneous signature flag is a binary element.

According to another particular embodiment of the invention, said erroneous signature flag is a counter, reset in the presence of a positive authentication decision and incremented in the presence of a negative authentication decision.

Thus, the erroneous signature flag that is allocated in a non-volatile memory of the portable object can be either a binary element or a counter, which allows a simple, relatively inexpensive and reliable implementation of the invention. .

In particular, said delay may be proportional to the value of said counter.

Thus, the delay applied by the portable object can be increased gradually, so as to increase the difficulty for the fraudster.

The invention also relates to a computer program product stored on a portable object and / or executable by a microprocessor, comprising program code instructions for performing the steps of the authentication method described above.

Finally, the invention relates to a secure portable object adapted to the setting of the process described above according to claim 7

• des moyens d'écriture, dans ledit indicateur de signature erronée, d'une valeur indiquant une situation anormale, si ladite décision d'authentification est négative ; et
• des moyens de génération d'un retard, si ledit indicateur de signature erronée contient une valeur indiquant une situation anormale.

According to one particular aspect of the invention, said portable object comprises:

• means for writing, in said erroneous signature flag, a value indicating an abnormal situation, if said authentication decision is negative; and
• means for generating a delay, if said erroneous signature flag contains a value indicating an abnormal situation.

According to yet another particular aspect of the invention, said non-volatile memory of the portable object is an EEPROM or Flash type memory.

5. List of figures

• la figure 1 illustre un exemple de système mettant en oeuvre l'invention selon un mode de réalisation particulier de l'invention ;
• la figure 2 présente les étapes principales du procédé d'authentification selon un premier mode de réalisation ;
• la figure 3 présente les étapes principales du procédé d'authentification selon un second mode de réalisation.

Other features and advantages of the invention will emerge more clearly on reading the following description of two particular embodiments, given as simple illustrative and non-limiting examples, and the appended drawings, among which:

• the figure 1 illustrates an exemplary system embodying the invention according to a particular embodiment of the invention;
• the figure 2 presents the main steps of the authentication method according to a first embodiment;
• the figure 3 presents the main steps of the authentication method according to a second embodiment.

6. Description of embodiments of the invention 6.1 General principle

The general principle of the invention is based on the use of an erroneous signature indicator stored in a non-volatile memory of a portable object, which can not be modified by a power interruption. The value of the control indicator according to the invention the duration of the authentication method of a carrier of the portable object, by imposing a delay, or a delay, systematic if the previous authentication attempt had delivered a wrong result .

6.2 Example of a system implementing the invention

The following is a part of a particular embodiment of the invention, in connection with the figure 1 , according to which the portable object is a smart card 7, which is a payment card issued by a bank, communicating with a payment terminal 2 (smart card reader terminal).

The holder of the smart card 7, which can be either the authorized user of the smart card 7 or a fraudster, wishes to access a banking service that requires it to be authenticated beforehand through the payment terminal 2. For example, this service may be the payment of a product or service by the holder to a merchant by means of the smart card 7 via the payment terminal 2.

The payment terminal 2 can be connected to a remote server 1, which is for example located in a bank, via a communication network 9 which therefore allows the exchange of information between the payment terminal 2 and the server 1. Bank-owned remote server 1 allows secure electronic transactions and can be connected to multiple payment terminals.

Conventionally, the payment terminal 2 is electrically powered by an electrical distribution network and / or by one or more batteries or batteries integrated in the payment terminal 2. The payment terminal 2 generally comprises a display screen 5, a numeric or alphanumeric keypad 3, a card reader 4, a central processing unit (CPU) and a printer (not shown).

The smart card 7 comprises a plastic-type support 6 and at least one integrated circuit (chip) 8 which is generally located in the body of the card 7. The integrated circuit 8 of the smart card 7 comprises an interface 12, which is generally in the form of copper electrical contacts, allowing a power supply of the payment terminal 2 and the exchange of information, in the form of electrical signals, when the card is inserted in the card reader 4 of the payment terminal 2.

For the holder of the smart card 7 can obtain authorization by the bank issuing the smart card 7 to make a payment, it is him necessary to authenticate as being the holder of the smart card 7 or the authorized user.

To do this, the carrier inserts the smart card 7 in the card reader 4 of the payment terminal 2 provided by the merchant and enters his confidential code (signature) through the keyboard 3 of the payment terminal 2.

The microprocessor of the smart card 7 performs a comparison processing, or authentication, according to a control algorithm known to those skilled in the art, taking into account the code issued by the carrier through the keyboard 3 and the secret information derived from the confidential code contained in a ROM memory of the smart card 7, and where appropriate random data provided by the payment terminal 2. The microprocessor of the smart card 7 then issues the payment terminal 2 an authentication decision information, depending on whether the delivered signature is correct or erroneous.

When the secret information stored in the smart card 7 matches the signature issued by the carrier, the secure electronic transactions (or any other operation) are authorized, under the control of the terminal 2 and / or the remote server 1.

The smart card conventionally comprises a microprocessor and various RAM and ROM memories. It also comprises, according to the invention, a non-volatile modifiable memory, for example an EEPROM 14.

The invention therefore proposes to use an erroneous signature indicator (I), which may be a binary element, such as a memory bit. The bit is stored in the EEPROM 14 of the smart card 7. The bit can also be stored in a Flash type memory or any other type of non-volatile memory.

6.3 First example of implementation

We present below, in relation to the figure 2 , the main steps of a method of authenticating a carrier of a portable object according to a first particular embodiment of the invention. We therefore place ourselves in the following in a configuration where the smart card 7 is inserted in the card reader 4 of the payment terminal 2.

As illustrated in figure 2 the authentication method according to the invention starts with a new step, which does not exist in the techniques of the prior art, namely the reading (21) of the erroneous signature flag, hereinafter called I, in the location of the EEPROM memory 14 allocated to it. Depending on the value of this indicator I (test 22), the smart card 7 decides itself (that is to say without the intervention or control of the payment terminal 2) to apply or not a delay, or delay, before performing the standard authentication processing.

Thus, in the case where a value 0 of the indicator I signals a correct situation, and the value 1 an abnormal situation, the output "yes" (221) of the test "I = 0" (22) allows a direct passage without delay, in the conventional authentication step (23), which will compare the signature S issued by the user using a suitable interface (for example a keyboard) to the data present in the smart card. 7. This treatment, known per se and applied in all smart cards, is not described in more detail here. The skilled person will know, depending on the circumstances, implement the appropriate authentication algorithm.

On the other hand, in the case where the indicator I is equal to 1, the output "No" (222) of the test (22) leads to the generation of a delay (24) which may for example be between 10 and 60 seconds. At the end of this delay (24), the value of the indicator I is repositioned to 0 (step 25), then the conventional authentication processing (23) is resumed.

This authentication process (23) delivers information representative of the result of the authentication. If the authentication is validated (test 26), the transaction (27) can be performed in a conventional manner. This transaction can be a payment, authorization to access data or a site, ... If the authentication is not correct (261), the payment terminal 2 implements a suitable processing (28) which is not the subject of the present invention. It can for example count the number of authentication errors, and prevent to achieve, for example, more than three attempts. However, this treatment being carried out by the payment terminal 2, it can easily be hijacked or canceled by a fraudster who has adapted his terminal to enter, without limitation, a very high number of signatures, for example randomly, hoping to find the right one in a reasonable time.

For this reason, according to the invention, prior to this processing (28) the writing (29) of the value 1 in the indicator I of the smart card 7 is carried out.

Thus, even in the case where the fraudster has adapted his payment terminal 2, or in the case where he has several terminals that he plans to use successively, he will be confronted with a waiting period, generated by the card chip 7 itself, preventing the realization of an automated series of signature tests in a reasonable time.

The delay, or delay, applied is chosen so that it is long enough to deter fraudsters, without introducing too much discomfort for the authorized user, who would have simply made a typing error.

6.4 Second implementation example

According to a variant of the method described above, it can be provided that the indicator I is not a simple binary element, indicating whether the previous signature was erroneous or valid, but a counter, accounting for the number of successive erroneous signatures. This can gradually increase the delay applied by the smart card 7, so as to limit the nuisance for the authorized user, and increase the difficulty for the fraudster. This counter may also allow, if necessary, when it has reached a threshold, to cause a definitive blocking of the smart card 7 (again, managed by itself, and not by the terminals).

This approach is illustrated by the figure 3 . The method starts, in the same manner as in the first embodiment, by the reading (21) of the indicator I. A test (31) is performed on the value of the latter. If it is 0, the authentication process (23) is performed in the same way as in the first embodiment. If the result of the test (31) indicates (312) that the value I is different from 0, the smart card 7 generates a delay (32), during which it will not do any processing. This delay is no longer fixed, but depends on the value of I. For example, a linear function, a step function, or an exponential function can be provided.

Once the delay (32) has elapsed, we go to the authentication step (23), then we test (26) on the result of the authentication. If the result of this test (26) is correct, that is to say that the provided signature is authenticated, the value of the indicator is repositioned (34) to 0, then the transaction (27) is carried out.

On the other hand, if the result of the authentication (26) is negative (261), the value of I is incremented (33) before performing the erroneous signature processing (28) in the terminal.

6.5 Variants

If the authentication is not correct (261), the writing (29, 33) in the indicator I of the smart card 7 may also include a storage operation in a non-volatile memory (the EEPROM 14 by example) of the smart card 7 of at least one information relating to the context, such as the date and time and / or an identifier of the payment terminal used. The reading step 21 of the indicator I may comprise a step of reading the information relating to the context that may be stored in the smart card 7 and the delay (24, 32) may be a function of this information.

In other embodiments, the portable object may be a USB key and the electronic terminal may be a laptop or a personal computer for example.

The signature can be entered by means other than a keyboard (touch screen, voice command, ...).

The connection between the terminal and the portable object can be made by contact or remotely (RFID for example).

The present invention can also be applied to any situation requiring a restriction of access to a protected place or premises, to a vehicle belonging to one or more persons, a website or a database, for example.

Claims (9)

A method of authenticating a carrier of a portable object comprising means for storing at least one secret information, comprising the following steps: authentication processing of a signature issued by said bearer, taking into account said secret information; - issuing an authentication decision information, positive or negative, the method implementing implements, in a non-volatile memory of said portable object, an erroneous signature indicator that can take a value indicating a normal situation and at least one value indicating an abnormal situation, and comprising: after said delivery step, a step of writing, in said erroneous signature flag, a value indicating an abnormal situation, if said authentication decision is negative; and before said authentication step, and if said erroneous signature flag contains a value indicating an abnormal situation, a step of generating a delay, characterized in that said writing step also comprises an operation for storing at least one information relating to the context, such as the date and time and / or an identifier of the terminal used. Authentication method according to claim 1, characterized in that it comprises, after said step of generating a delay or after said step of issuing: a step of writing, in said erroneous signature flag, said value indicating a normal situation Authentication method according to any one of claims 1 and 2 characterized in that said erroneous signature indicator is a binary element. Authentication method according to any one of claims 1 and 2
characterized in that said erroneous signature flag is a counter, reset in the presence of a positive authentication decision and incremented in the presence of a negative authentication decision. Authentication method according to claim 4, characterized in that said delay is proportional to the value of said counter. Computer program product stored on a portable object and / or executable by a microprocessor, characterized in that it comprises program code instructions for performing the steps of the authentication method according to any one of claims 1 at 5. Secure portable object comprising: means for memorizing at least one secret information; means for authenticating a signature delivered by said bearer, taking into account said secret information; means for issuing an authentication decision information, positive or negative, means for non-volatile storage of an erroneous signature indicator that can take a value indicating a normal situation and at least one value indicating an abnormal situation, characterized in that it comprises means for storing at least one piece of information relating to the context, such as the date and time and / or an identifier of the terminal used. Portable object according to claim 7, characterized in that it comprises: means for writing, in said erroneous signature flag, a value indicating an abnormal situation, if said authentication decision is negative; and means for generating a delay, if said erroneous signature flag contains a value indicating an abnormal situation. Portable object according to any one of claims 7 and 8, characterized in that said non-volatile memory is an EEPROM type memory or Flash.

Images