EP1866859A2

EP1866859A2 - Making secure data for customer loyalty programmes

Info

Publication number: EP1866859A2
Application number: EP06726214A
Authority: EP
Inventors: Benjamin Morin; Sébastien CANARD; Fabrice Clerc
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2005-03-03
Filing date: 2006-03-02
Publication date: 2007-12-19
Also published as: WO2006092539A2; US20090012900A1; WO2006092539A3

Abstract

The invention concerns a portable device, a terminal, a system and a method for recording data concerning a transaction through the terminal (1) of a merchant on a portable device (3) of customer loyalty with a group of at least one merchant, said transaction being recorded by the said merchant terminal (1) on the portable device (3), in accordance with the following steps, implemented in any particular order: a first recording corresponding to said transaction encrypted with an encryption key (C1) of the customer, and a second recording corresponding to said transaction encrypted with a key (M1) associated with said group to which said merchant belongs.

Description

Data security for customer loyalty programs.

TECHNICAL FIELD OF THE INVENTION The invention relates to the field of securing computer data, and relates in particular to the field of electronic and computer equipment for customer loyalty with at least one group of at least one trader.

Background of the invention

To retain their customers, merchants often use media capable of recording the transactions made with their customers, for the benefit of benefits. The amount and nature of the benefits depend on the loyalty strategy adopted by the merchants and may be a function of a number of transactions, a cumulative amount of expenses, etc.

In general, loyalty systems have in common a mechanism capable of recording all or part of the data related to customer transactions at a merchant. This data includes for example the price of each item, the total amount of the transaction, the number of items, the reference of each item, etc. These data are used to calculate a benefit offered to a customer.

The media or loyalty cards used to record the data, are more or less elaborate, ranging from a simple card buffered by the merchant to each transaction, to magnetic cards.

Non-exclusively, the transaction data can be stored at the merchant or on the customer's support In the case where the transaction data is exclusively stored at the merchant, the loyalty card is used to identify customers. The security of the loyalty system (in particular the protection against fraud) is guaranteed by the security of the underlying storage medium used by the merchant (for example a computer database). However, this approach has several disadvantages. First, security does not protect customers from dishonest merchants, who could for example remove transactions in order not to give their customers the benefits they deserve. In addition, it does not allow customers to know at any time the status of their loyalty points. Finally, this approach requires the merchant to implement a loyalty infrastructure that can be complex.

Conversely, the storage of transactional data on a support owned by the customer does not require the establishment of a complex infrastructure at the merchant and allows customers to know the status of their loyalty points. However, as each merchant has its own loyalty card system, customers must necessarily keep a multitude of loyalty cards in order to benefit from the offers. What's more, certain media require the customer to memorize an access code (PIN code).

From the point of view of security, it is necessary to guarantee the merchants the authenticity of the transactional data. In the case of paper media, the use of a merchant's own logo and a stamp guarantee a form of authenticity, but these characteristics are generally simple to falsify. In the case of more sophisticated media (magnetic cards for example), it is the concealment of data structures and / or technical difficulties in implementing fraud that guarantee security but not in a sufficient manner. Several works focus on the concept of electronic loyalty card. For example, the patent FR2810760 proposes a computer system for customer loyalty comprising a plurality of terminals for merchant equipment, and a plurality of loyalty cards for customers. The terminals include a memory for registering a loyalty program and recording means for recording data corresponding to a commercial transaction in the memory of the loyalty card.

However, this system does not have sufficient security to guarantee merchants the authenticity of transactional data.

Documents GB2397678 and EP0992924 provide secure loyalty card schemes, but the security features relate only to the confidentiality of customer-specific data contained on the card, and do not guarantee security against possible fraud on the part of cardholders. clients.

US66549912 provides a file structure for storing transactions on any type of loyalty card (laptop, smart card, etc.). Only the confidentiality of transactions is evoked and implemented using passwords stored directly on the card by the merchant. Transactions are therefore only accessible by the latter.

The document FR2804228 does not propose a secure scheme of a loyalty card, but only a method of displaying the information contained on a loyalty card to enable a customer to know the status of his privileges at the merchants.

The invention therefore relates to a method for recording data relating to a transaction by a merchant's terminal on a portable device for customer loyalty with at least one group of at least one merchant, said transaction being recorded by the merchant's terminal on the portable device, according to the following steps, implemented in any order:

a first record corresponding to said transaction encrypted with a client encryption key, and a second record corresponding to said transaction encrypted with an encryption key associated with said group to which said merchant belongs.

Thus, the method according to the invention allows a customer to use the same portable fidelity device securely and universally in several merchants belonging to at least one group. Indeed, the first registration ensures that only the customer has access to all transactions and the second registration ensures that only merchants belonging to the same group can decipher the client's transactions with a partner. Advantageously, the method comprises a signature of said transaction with a private electronic signature key associated with said merchant.

Thus, the signing of the transaction guarantees the authenticity, integrity and non-repudiation of transactions. Said first record is decryptable by means of a decryption key of the client, and said second record is decryptable by means of said encryption key associated with said group to which said merchant belongs.

Advantageously, said data relating to the transaction comprise one or more information items selected from the set of the following information:

an identifier of the transaction allowing the non-cumulation of the advantages already granted to the customer,

a customer identifier to prevent a third party from enjoying the benefits illegitimately, - an identifier of the group of merchants to guarantee the universality of loyalty,

an amount of the transaction making it possible to implement loyalty operations according to the total amount spent by a customer at a merchant,

a date of the transaction making it possible to implement limited advantages over time,

a marker to indicate that the customer has already benefited from the benefits resulting from the transaction, or that the transaction is not invoiced, or that the transaction has been canceled, and

a product identifier for organizing loyalty operations based on particular products.

Merchants and customers are protected against possible fraud by merchants or dishonest customers. In addition, depending on the marking of the transaction, the portable loyalty device can be used as a reliable electronic estimate or receipt in addition to its use as a loyalty card.

The invention also relates to a method for reading secure data relating to transactions recorded by means of a secure data recording method according to the above characteristics and comprising the following steps:

decrypting said secure data by means of the encryption key associated with said group to which said merchant belongs, and verifying the authenticity of said transactions by means of the public signing key.

According to one particular aspect of the invention, data relating to transactions recorded on the portable loyalty device are provided as input to a specific loyalty program which after its execution returns information about the benefits granted to the customer for these transactions.

Thus, a merchant who participates in several separate partnerships may choose the loyalty program appropriate for specific transactions.

The invention also relates to a computer system for recording data relating to a transaction by a merchant's terminal on a portable device for the distribution of a clientele to at least one group of at least one merchant, the terminal the merchant being intended to record the data of said transaction on storage means of the portable device, via a first communication channel according to a data structure comprising:

a first record corresponding to said transaction encrypted with a client's encryption key; a second record corresponding to said transaction encrypted with a key associated with said group to which said merchant belongs.

Thus, the system according to the invention is a vectorization system having a universal character and comprises security properties. Advantageously, said data structure comprises a signature of said transaction with a private electronic signature key associated with said merchant.

Thus, the system has authenticity properties for merchants and customers. Advantageously, the system comprises a device accessed by the terminal of said merchant via a second communication channel, said device storing an identifier of said merchant and its public and private keys of electronic signatures.

Thus, the identifier and the public and private keys of signatures can be stored in a simple, secure and non-modifiable way. The system further includes a storage medium connected to the terminal via a third communication channel and storing encryption keys shared by members of the group to which the merchant belongs. Thus, the encryption keys can be shared in a simple and secure manner between several merchants belonging to the same group.

In addition, the system may include a key distributor distributing said encryption keys via a fourth communication channel.

Thus, encryption keys can be distributed confidentially and centrally to all merchants.

The system may also include a server for recording the transaction and / or encrypted coordinates of the client, said server being connected to the terminal via a fifth communication channel.

Thus, the security of the transaction is enhanced by additional registration and the customer's contact information can be used securely and centrally for business studies or advertising campaigns. The system may also include a loyalty program distributor connected to the terminal via a sixth communication channel and intended to distribute the loyalty programs.

Thus, loyalty programs can be distributed uniformly and centrally to each group of merchants according to the loyalty strategy adopted by each group.

The invention also relates to a portable loyalty device for a loyalty computer system according to the above characteristics and comprising a cryptographic calculation means and a storage means for storing the data relating to said transaction. Thus, the portable fidelity device gives the loyalty system a great simplicity of deployment for both the customer and the merchant.

The device also includes a read-only memory storing a client identifier and public and private encryption keys of the client and the storage means further includes personal data of the client stored in an encrypted manner with the public encryption key associated with the client so that access to this personal data is subject to the authorization of the said customer by means of a personal identification number.

Thus, the identifier and the public and private encryption keys of the client are stored in a simple, secure and non-modifiable manner and the personal data of the client are protected.

Advantageously, the device can be used as a loyalty card, an electronic quote, or a receipt according to a marking information included in the transaction.

Thus, the loyalty device guarantees the authenticity and non-repudiation of a commercial proposition and a reliable receipt.

The invention also relates to a terminal for recording data relating to a transaction on a portable device for customer loyalty with at least one group of at least one merchant, characterized in that said registration is carried out according to a data structure comprising:

a first record corresponding to said transaction encrypted with a client's encryption key,

a second record corresponding to said transaction encrypted with a key associated with said group to which said merchant belongs. Advantageously, said data structure comprises a signature of said transaction with a private electronic signature key associated with said merchant.

The invention also relates to a computer program downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor, characterized in that it comprises program code instructions for the performing the steps of the recording method according to at least one of the above features when executed on a computer or a microprocessor.

Brief description of the drawings

Other features and advantages of the invention will appear on reading the description given below, by way of indication but not limitation, with reference to the accompanying drawings, in which:

FIG. 1 illustrates a very schematic example of a loyalty system comprising a terminal and a portable loyalty device, according to the invention, and

FIG. 2 illustrates the loyalty system of FIG. 1 further comprising key and loyalty program distributors and a server.

Detailed description of embodiments

According to the invention, FIG. 1 illustrates a very schematic example of a computer system for recording data relating to a transaction by a merchant's terminal on a portable loyalty or customer loyalty device with a customer. at least one group of at least one merchant. Indeed, the loyalty system is valid for a plurality of groups and each group is defined by a particular partnership between several merchants. So, a partnership is a loyalty operation organized by a group of merchants, which consists in giving customers the benefit of benefits valid for all the merchants of this group. Such a partnership may for example exist between a hairdresser and a seller of beauty products. Through partnerships, the invention also naturally takes into account the case where merchants are part of the same commercial brand. This allows a customer to benefit from its advantages at several different merchants who belong to the same commercial brand.

Of course, a merchant can be a member of different distinct groups, and moreover, a group can be reduced to a single merchant.

The loyalty computer system according to the invention comprises a plurality of electronic terminals 1 intended to equip merchants and a plurality of portable loyalty devices 3 intended for customers.

The electronic terminal 1 of a merchant belonging to said at least one group includes a memory 5 for the recording of at least one loyalty program P1, P2 and means 7 for reading, writing and processing to execute the programs Pl, P2 of loyalty. A loyalty program (or loyalty program) is a computer program that delivers information relating to a benefit granted to the customer based on the transactions made by the customer with the merchant.

Thus, the loyalty program implements a loyalty strategy specific to the merchant or group of merchants, according to a set of rules defining the conditions for benefiting from the benefits, their nature and their amount (for example 5% of purchase on the merchant or merchant group). all of the last ten purchases, or a gift given after five purchases, etc.). A loyalty strategy is a function of several parameters, such as the number of transactions, the cumulative amount of transactions, or a period of validity of transactions.

Of course, a terminal 1 is capable of executing several loyalty programs Pl, P2, for example, so that a merchant participating in several different partnerships can choose the loyalty strategy that is appropriate for a given transaction.

The means 7 for reading, writing and processing the electronic terminal 1 of a merchant, to record the transaction between the merchant and the customer on a storage means 9 of the device 3 portable customer loyalty. Indeed, the portable fidelity device 3 interacts with the merchant's terminal 1 via a first communication channel Ll which can be electrical, magnetic, optical, radio, infrared, or other.

Data relating to each transaction is recorded according to a secure data structure comprising a first encrypted record of the transaction, a second encrypted record of the transaction, and advantageously a signature of the transaction.

The first record corresponds to the transaction encrypted with a public encryption key C1 of the client, the second record corresponds to the transaction encrypted with a symmetric encryption key Ml associated with the group to which the merchant belongs, and the signature of the transaction is carried out with a private electronic signature key M2 associated with the merchant.

In addition, the first record can be decrypted by means of a private decryption key C2 of the client, the second record is decryptable by means of the symmetric encryption key M1, and the signature is verifiable by means of a corresponding public key M3. to the private key of electronic signature M2.

The encryption of the transaction with the key Cl ensures that only the customer has access to all of his transactions, which he can decipher at using his secret key C2. The transaction coding with the Ml key ensures that only merchants belonging to the same group can decrypt the customer's transactions with a partner (and only those transactions). Finally, signing the transaction guarantees the authenticity of the transaction, that is, a dishonest customer can not forge a dummy transaction.

In addition, the transaction can be considered as a / 7-tuple that may include a merchant identifier (or group of merchants as part of a partnership), a customer identifier, a transaction identifier, a product identifier, a amount of the transaction, a date of the transaction, and a marker.

The identity of the merchant uniquely identifies the merchant (or group of merchants) and thus guarantees the universality of the portable 3 fidelity device. The customer identifier uniquely identifies the owner of the portable loyalty device 3. The presence of the customer's identity in each transaction prevents a customer from fraudulently transferring its benefits to a third party. The identity of the customer in each transaction recorded on the portable device 3 must be the same as that of the owner of this portable device 3. This correspondence can be verified by the merchant when providing a benefit to a customer.

The function of the transaction identifier is to prevent a customer from forging fake purchases by duplicating transaction records. The transactions recorded on the portable fidelity device 3 must at least differ by their transaction identifier so that a fraud can be characterized by the existence of two identical transactions. The transaction identifier may be a value assigned by the merchant terminal 1 at the time of the transaction. This value can for example be managed by a counter incremented with each transaction (depending on the client's identity or not).

Alternatively, the transaction identifier may be replaced by a number of units of the same product. A fraud would be characterized by the existence of multiple transactions of the same product, at the same time.

Thus, the transaction identifier allows the non-cumulation of the benefits already granted to the customer.

The presence of the amount in a transaction makes it possible to implement marketing operations which consist in giving the customers advantages according to the total amount spent by the customer at a merchant. The benefits that are dependent on the number of transactions are naturally supported by the portable fidelity device 3.

The presence of the date in the transaction makes it possible to implement advantages limited in time.

The product or service identifier is used to organize product-related marketing operations. This may be the number on bar codes, for example, or a descriptive string. It should be noted that the presence of the identity of the goods does not render the presence of the amount superfluous. Indeed, the amount of a commodity can change over time. Moreover, if the amount of the transactions was based solely on the identity of the goods, the merchants would be forced to possess a complex infrastructure recording the history of the evolution of the price of each commodity.

The function of the marker is to indicate the transactions that have been used by a customer to gain benefits. Its presence in the transactions prevents a customer from modifying his transactions in order to benefit illegitimately several times. The marker can also be used to mark transactions that are quotes (that is, not yet billed) and canceled transactions. The meaning of the markings can be indicated by a code table (for example: 0 = advantage used, 1 = estimate, 2 = transaction canceled). Thus, depending on the marking of the transaction, the portable loyalty device 3 can be used as a reliable electronic estimate or a reliable receipt in addition to its use as a loyalty card.

Then, each customer must own a portable fidelity device 3 equipped with a chip capable of performing cryptographic calculations ensuring the security properties of the loyalty system. Thus, in addition to the storage means 9 for storing the transaction record, the portable loyalty device 3 comprises a cryptographic calculation means 11 and a memory means (for example a read-only memory 13) for storing in a non-random manner. modifiable public and private keys Cl, C2 of client encryption as well as the client identifier.

Furthermore, it should be noted that the storage means 9 may also include personal data of the owner of the portable device 3 loyalty which are encrypted using its public key Cl. Access to these data is thus subject to the authorization of the customer, for example via a personal identification number (PIN).

The portable fidelity device 3 may be a smart card, a mobile phone, a personal assistant, or any other equipment comprising a cryptographic calculation means and a storage means.

Note that in the case where the portable fidelity device 3 is a smart card, the terminal 1 must be provided with a card reader. However, in the case where the portable device 3 fidelity is a mobile phone, the terminal 1 may for example be equipped with a Bluetooth type device to communicate with this portable device 3.

Advantageously, the chip of the portable device 3 of fidelity comprises a means of protection (physical or logical) granting the client only a right of reading on the storage means 9 of transactions and prohibiting the merchant to delete data contained in this storage means 9 of transactions.

According to a particular implementation of the invention, the client can not modify the data entered on the transaction storage means 9 if each of these data is numbered (a data being a new transaction or a consumed advantage) and if the Merchant keeps in memory, for each customer, the number of the last data entered. Using this mechanism, another particular implementation of the invention consists in having the client sign, by means of an electronic signature key, each of the transactions entered by the merchant, thus preventing the merchant from deleting data from the merchant. fraudulent way.

In addition, the loyalty system comprises an integrated circuit device 15 (for example a smart card) to which the terminal 1 of a merchant accesses via a second communication channel L2 (fllear, optical, radio, infrared, magnetic, etc.). This integrated circuit device 15 is intended to store in a secure and non-modifiable manner the public and private keys of electronic signatures M2, M3 of the merchant as well as the identifier of the merchant (or group of merchants).

In addition, the loyalty system comprises a secure storage medium 17 connected to the merchant's terminal 1 via a third secure communication channel L3 and storing the symmetrical encryption keys M1 shared by the groups to which the merchant belongs. FIG. 2 shows that the loyalty system may further comprise a key distributor 19 distributing the symmetric encryption keys M1 via a fourth communication channel L4. According to this modality, the distribution of the encryption keys in the case of partnerships or signs is provided by this trusted key distributor 19 via any secure communication channel.

As a variant, the electronic terminal 1 of one of the members of a merchant group comprises a production means (not shown) intended to generate a symmetric encryption key M1 and then to transmit it securely to the other members of the partnership. . Another possibility would be a joint and secure calculation of the symmetric encryption key M1 by all members of the merchant group. According to one particular embodiment of the invention, the terminal

1 of the merchant can be connected via a fifth secure communication channel L5 to a server 21 responsible for recording the transactions and possibly the coordinates of the customers. These coordinates that come from the client are communicated in an encrypted manner and their access is subject to the agreement of the customer, via a PIN code. Customer contact information can be used for marketing research purposes or customized advertising campaigns.

In addition, the loyalty system comprises a distributor 23 of programs P1, P2, P3 connected to the terminal 1 via a sixth communication channel L6 and for distributing the loyalty programs that are loaded into the memory of the terminal 1. Where appropriate encryption key distribution and loyalty program distribution functions can be provided by the same entity. The loyalty programs Pl, P2, P3 are executed at each transaction, at the request of a customer wishing to benefit from its advantages, or at the initiative of the merchant.

The parameters necessary for the implementation of any loyalty strategy can be reduced to the data stored on the portable device 3 of fidelity.

To give a customer a benefit at the time of one or more transactions, the merchant executes a loyalty program loaded in his terminal 1. The valid transactions recorded on the portable device 3 fidelity are provided as input to the program specific that after its execution returns information about the benefits granted to the customer for those transactions.

Indeed, the loyalty program obtains the transactions made from the merchant or one of its partners by decrypting the recordings stored on the portable device 3 by means of the merchant's symmetrical encryption key Ml. Then, the loyalty program verifies the authenticity of the transactions using the M3 merchant's public electronic signature key. After verification, the loyalty program selects valid transactions, that is, those that have not been marked as already used to provide a benefit to the customer. Valid transactions for which the customer wants a benefit are provided as input parameters to the program that implements the branding strategy and in return gives the amount of the benefit. The new transactions are encrypted, signed and recorded on the portable fidelity device 3 and, where appropriate, the antecedent transactions used to benefit from the advantage are marked, encrypted and signed.

As an example, consider a merchant applying a loyalty strategy that consists of offering its customers a 20% reduction in cumulative past spending less than one year. The discount applies to the price of an item chosen by the customer (this 20% can not exceed the price of the item in question).

It is assumed that the merchant has previously downloaded to his terminal 1 the loyalty program Pl, P2, P3 implementing this strategy.

Consider a customer who has already purchased three items from this merchant in the last six months. When buying his fourth item, the customer wants the benefit to which he is entitled. The customer presents the portable device 3 loyalty to the merchant. The terminal 1 of the latter attempts to decrypt each of the transactions of the portable fidelity device 3 using a symmetric encryption key Ml of the merchant only, in fact, the loyalty strategy relates to purchases made at this merchant exclusively (if the merchant had been partner of other merchants, the terminal would have used the key of encryption idoine, on indication of the merchant).

The merchant terminal then verifies the authenticity of the transactions using the merchant's M3 signature public key, using a signature verification protocol.

The next step for Terminal 1 is to select "eligible" transactions to calculate the benefit, in this case expenditures of less than one year that have not already been used to benefit. Once this transaction list is extracted, the terminal 1 calculates 20% of the sum of the expenses.

Once the discount is made on the new item, the three items used to qualify for the benefit are marked invalid to prevent the customer from reusing them later. These changes are encrypted and signed.

In turn, the new purchase is recorded on the portable device 3 loyalty, signed and encrypted. Remember that transactions are stored in two versions. A version corresponds to the transaction encrypted with the client's public key to enable him to consult all his purchases. The other version corresponds to the transaction encrypted with an encryption key chosen by the merchant (his or shared with partners of the same group).

At any time, the customer can view all the transactions that are recorded on the portable device 3 of fidelity. Thus, a customer can see the benefits he can enjoy before going to a merchant.

For example, the customer may have a display terminal for accessing and displaying the transactions recorded on his portable loyalty device 3. On request of the display terminal and after authorization of the customer for example, by means of a PIN code, the portable loyalty device 3 decrypts the transactions previously encrypted with the client's public key and sends them back to the display terminal. , who displays them.

In the case where the portable device 3 fidelity is implemented using a mobile phone, the latter can also act as a terminal. In the case where the portable fidelity device 3 is a smart card, a dedicated display terminal is required. It can be a device connected to a personal assistant or a personal computer, or even a card reader with a screen.

In the case where the portable device 3 of fidelity is used as an electronic estimate, the customer comes to a first merchant. The merchant signs and encrypts a business proposal (a transaction) for a specific item or service. This article or service is marked as not yet billed, so that a customer does not pass a quote fraudulently for a transaction. The quote is finally saved on the device 3 loyalty notebook. The customer can prove the authenticity of the offer at a competing merchant. To do this, the customer consults the offer made by the first merchant using his display terminal and presents it to the second merchant. Thus, the electronic quote guarantees merchants the authenticity of competing commercial proposals made to customers in the event of negotiation and to customers, the non-repudiation of a commercial proposal made by a merchant.

Furthermore, to use the portable fidelity device 3 as a reliable electronic cash receipt, the customer presents his portable device 3 to the merchant to whom he wishes, for example, to bring back an article. As in the case of a purchase, the merchant's terminal 1 accesses the transactions recorded on the customer's portable device 3 of loyalty. The merchant is sure of the authenticity of these purchases, since he signed them during the transaction. If the merchant accepts the return of the item, the transaction is marked as canceled. Thus, the electronic sales receipt guarantees the merchants the authenticity of their own identity in the transactions recorded on the portable device 3 and the customers the non repudiation of a purchase by a merchant in bad faith. Thus, the present invention provides a method, system and universal loyalty device for implementing any loyalty strategy. The use of portable customer-owned loyalty devices makes deployment easy for both the customer and the merchant. Merchants only need a terminal capable of reading transactions stored on the customer's device that can take the form of, for example, a smart card, mobile phone, or other mobile security device .

In addition, the portable fidelity device can also be used as a receipt or as a quote. In addition, any transaction has security properties

(authentication of purchases, non-accumulation of benefits, non-repudiation of transactions by a merchant, confidentiality of transactions and confidentiality of personal data) protecting both merchants and customers against fraud.

It should be noted that the steps of the recording method according to the invention can be performed by code instructions of a computer program when it is executed on a computer or a microprocessor. This computer program can be downloaded from a communication network and / or stored on a computer readable medium.

Claims

1. A method of recording data relating to a transaction by the terminal (1) of a merchant on a portable device (3) for customer loyalty with at least one group of at least one merchant, characterized in that said transaction is recorded by the terminal (1) of said merchant on the portable device (3), according to the following steps, implemented in any order: -a first record corresponding to said transaction encrypted with an encryption key (Cl) of the customer, and

a second record corresponding to said transaction encrypted with an encryption key (Ml) associated with said group to which said merchant belongs.

2, Method according to claim 1, characterized in that it comprises a signature of said transaction with a private electronic signature key (M2) associated with said merchant.

3. Method according to claim 1, characterized in that said first record is decryptable by means of a decryption key (C2) of the client, and in that said second record is decryptable by means of said encryption key (Ml) associated with said group to which the merchant belongs.

4.Procédé according to any one of claims 1 to 3, characterized in that said data relating to the transaction comprise one or more information selected from the set of the following information: an identifier of the transaction allowing the non-cumulation of the advantages already granted to the customer,

a customer identifier to prevent a third party from benefiting illegitimately, an identifier of the merchant group to guarantee the universality of the spread,

an amount of the transaction making it possible to implement trivialization operations according to the total amount spent by a customer at a merchant, a date of the transaction making it possible to implement advantages limited in time,

a marker to indicate that the customer has already benefited from the benefits resulting from the transaction, or that the transaction is not invoiced, or that the transaction has been canceled, and a product identifier for organizing the operations of according to particular products.

5. A method for reading secure data relating to transactions recorded by means of a method according to any one of claims 1 to 4, characterized in that it comprises the following steps:

-deciphering said secure data by means of said encryption key (Ml) associated with said group to which said merchant belongs, and -checking the authenticity of said transactions by means of a public signature key (M3).

6. Method according to claim S ₁ characterized in that data relating to transactions recorded on the portable device (3) of fidelity are provided as input to a specific software program which after its execution returns information about the benefits granted to the customer for these transactions.

7. Computer system for recording data relating to a transaction by the terminal (1) of a merchant on a portable device (3) of customer loyalty with at least one group of at least one merchant, characterized in that the merchant terminal (1) is for storing the data of said transaction on storage means

(9) of the portable device (3), via a first communication channel (L1) according to a data structure comprising:

a first record corresponding to said transaction encrypted with an encryption key (C1) of the client,

System according to claim 7, characterized in that said data structure comprises a signature of said transaction with a private electronic signature key (M2) associated with said merchant.

9. System according to any one of claims 7 and 8, characterized in that it comprises a device (15) which accesses the terminal (1) of said merchant via a second channel (L2) communication, said device storing an identifier said merchant, his private electronic signature key and a public electronic signature key.

10. System according to claim 5, further comprising a storage medium connected to the terminal via a third communication channel and storing encryption keys (Ml) shared by the members of the group to which the merchant belongs.

11. System according to claim 10, characterized in that it comprises a distributor (19) of keys ensuring the distribution of said encryption keys (Ml) via a fourth channel (L4) communication.

H.System according to any one of claims 7 to 11, characterized in that it further comprises a server (21) for recording the transaction and / or customer encrypted data, said server being connected to the terminal via a fifth communication channel (L5).

13. System according to any one of claims 7 to 12, characterized in that it further comprises a program distributor (23) connected to the terminal (1) via a sixth channel (L6) of communication and intended to distribute the loyalty programs.

14. Loyalty device (3) for a loyalty computer system according to any one of claims 7 to 13, characterized in that it comprises a cryptographic calculation means (11) and a storage means (9) for storing data relating to said transaction.

15. Device according to claim 14, characterized in that it comprises a read-only memory (13) storing a client identifier and public and private encryption keys (C1, C2) of the client and in that the storage means ( 9) further includes personal customer data stored encrypted with the public encryption key (C1) associated with the customer so that access to such personal data is subject to the authorization of the said customer by means of a personal identification number.

16. Device according to any one of claims 14 and 15, characterized in that said device is used as a loyalty card, an electronic quote, or a receipt according to marking information included in the transaction.

17.Portable device (3) customer loyalty with at least one group of at least one merchant characterized in that it comprises a storage means (9) for storing registration data relating to a transaction involving;

a first record corresponding to said transaction encrypted with a client's encryption key (C1); a second record corresponding to said transaction encrypted with an encryption key (Ml) associated with said group to which said merchant belongs.

18. Device according to claim 17, characterized in that said registration data comprises a signature of said transaction with a private electronic signature key (M2) associated with said merchant.

19. Terminal (1) for recording data relating to a transaction on a portable device (3) for customer loyalty with at least one group of at least one merchant, characterized in that said registration is realized according to a data structure comprising:

a first record corresponding to said transaction encrypted with an encryption key (C1) of the client, a second record corresponding to said transaction encrypted with an encryption key (Ml) associated with said group to which said merchant belongs.

2O.terminal according to claim 19, characterized in that said data structure comprises a signature of said transaction with a private electronic signature key (M2) associated with said merchant.

21. Computer program downloadable from a communication network and / or stored on a computer readable medium and / or executable by a microprocessor, characterized in that it comprises program code instructions for the execution of the steps of the recording method according to at least one of claims 1 to 6, when executed on a computer or a microprocessor.