WO2008003886A1

WO2008003886A1 - Electronic module for storing data

Info

Publication number: WO2008003886A1
Application number: PCT/FR2007/051514
Authority: WO
Inventors: Patrick Picard
Original assignee: France Telecom
Priority date: 2006-07-06
Filing date: 2007-06-25
Publication date: 2008-01-10
Also published as: FR2903509A1

Abstract

The invention relates to a method of managing access of an entity to at least one item of data stored on a memory module. According to the invention, access is preceded by a prior allocating step able to allocate said at least one data item an access entitlement level that said entity must possess in order to access this data item. This prior step is followed by a step of accessing said at least one data item by an entity, the access consisting in verifying that the entity possesses a sufficient access entitlement level.

Description

Electronic module for data storage Technical field

The invention relates to the field of storing data, in particular identity data, on an electronic module, and managing access to these data.

The module can take many forms. The chosen form can be indifferently

a memory capable of being coupled to a data processing device able to manage the data stored in the memory; such a memory is, for example, a non-volatile memory of the EEPROM type, Flash-EPROM, etc. Today we find memories of this type sold for example as the USB key (Universai Sériai Bus), or MMC card (Multimedia Memory Gard).

a memory incorporated in a data processing device; for example a smart card.

State of the art

Current procedures for issuing identity cards and passports are not sufficiently secure. Thefts of blank titles take place every year. Authentic titles are also issued improperly on the basis of false certificates of civil status or from real usurped certificates. This identity fraud serves to carry out multiple offenses; illegal immigration, social or welfare allowance fraud, scams, banditry. The cost of such fraud amounts to hundreds of millions of euros a year.

To combat this type of fraud, some states are considering replacing the paper-based identity card with an electronic module storing identity data. The form chosen by many states for this module is that of the smart card. This card would not only store classic identity data as found on a traditional paper identity card, but also complementary identity data. For example, conventional identity data as the French state plans to store on this card are name, surname, date of birth, place of birth, sex, address, handwritten signature _s Prefecture having issued the card, the card number. Additional identity data will include

- data relating to a driving license, a registration certificate, a voter's card,

- a photograph,

- digitized fingerprints,

- etc.

This card will also store personal order data. Personal information, unlike identity data, is unofficial data but related to the owner of the smart card. This personal data may be related to the professional, commercial or personal environment of the card owner.

The applications of such an electronic identity card will be multiple namely the electronic signature, authentication, identification on the Internet, the applications of everyday life such as banking transactions, filling forms online, substitution to other papers such as driving license.

A plurality of entities will have access to the contents of this card to identify an individual: Administrations (gendarmerie, police, taxes, etc.), merchants, content providers via the Internet, etc.

The problem is that there is no access management to the contents of the card able to restrict, for a given entity, access to a subset of data stored on the card. For example, a trader should not have access only to traditional identity data and should not be allowed access to personal order data; Similarly, an administration should have access to all identity data but should not necessarily have access to the personal data stored on the card.

The invention

The present invention provides a solution that does not have this problem.

For this purpose, the invention proposes a method for managing the access of an entity to at least one piece of data stored on a memory module, characterized in that the access is preceded by a prior assignment step able to attribute to said less than one datum, a level of access rights that the entity must possess to access this datum; and in that it comprises an access step in which the entity accesses said at least one data item provided it has a sufficient level of access rights.

At least one piece of data stored on the card is thus associated with a level of access rights that an entity must have to access this datum. It is therefore possible to restrict access to the contents of the module to a subset of data.

Thanks to the invention, it is conceivable to store on the same module all kinds of data, whether they are used

- for identity purposes with reference to the identity card, the passport, the driving license

- or for professional purposes for the storage of access rights to a site, etc.

- commercial for customer profile storage, etc;

- or any other applications requiring data storage. According to one embodiment of the invention, the assignment consists in encrypting the said at least one piece of data by means of an encryption key, and in that, during the access step, the entity accesses the said item. least one data provided that it has the decryption key able to decrypt the result of the encryption of said at least one data. Thus, an encryption / decryption key is shared between the module and the entity; access to data will only be allowed if the entity has the key capable of decrypting the encrypted data.

According to a particular embodiment of the invention, when the module stores at least two data items (DT1, DT2, ..., DTi + 1, DTi, ... DTn) associated with a respective access right level (N1, N2 , N3, Ni + 1, Ni, ..., Nn), said levels verifying the following mathematical relationship

N1c N2c ... c = Ni + 1c Nic ... c Nn (n≥1), each level (N1, N2, N3,

Ni + 1, Ni, ..., Nn) being associated with at least one respective encryption key

(KI ₁ (K1.K2), ..., {K1, ..., KH-I) ₁ (K1, ..., Ki), ... (K1 Kn) ₅ the encryption of a data item DTi associated with a level of entitlement Ni advantageously comprises a succession of encryption according to the following relationship

R, = E _Kι [DTi] for the encryption of the order data i

and the following recursive relation: R, ^ = E _{X 1} [DT ₁ ^ R,],

- Fressing the result of the encryption of at least the data DT,;

- R ₍ _, being the result of the encryption of at least the set including the data DT _1-1 and the result of the previous encryption performed R,;

- E _Kl is an encryption function, the index indicating the key used for encryption; and in that the step of accessing said at least one data DTi, DT _1-1 , ..., DT1 comprises a succession of decryptions of the relationships with said at least one encryption key associated with the level Ni.

This characteristic is interesting because the access to a data DTi of a given level "i" requires your knowledge of at least one key. The higher the access entitlement level, the greater the number of keys to be known. Access to a given level of data will be all the more difficult as the level in question is high.

According to one embodiment of the invention, when an entity wishes to access a piece of data, this entity indicates the order of use of the said at least one key associated with a level for performing decryption, in that the the access step is preceded by a verification step of the indicated usage order, and in that the decryption is performed if the order is correct. Thus, if the encryption of a data DTi is carried out by means of a first key K ₁ and then the encryption of the data DT _1-1 is carried out with a second key K _1-1 and so on, the decryption will consist of using these keys in the reverse order to the one that served encryption; in this case, it is necessary first to decode DT _1-1 with K, _, and then DTi by means of the key

K,. In this way, even if a fraudster is aware of all the encryption keys associated with a level of rights, he should know the order of use of each key for decryption. This feature reduces the risk of fraud.

In a particular embodiment, the number of decryptions successively made is equal to the number of keys associated with the level of access right associated with the data. Thus, an entity associated with a given level of entitlement does not have the opportunity to attempt to access data of a level of law higher than the given level. This method of encryption and decryption is interesting because it may happen that the same encryption key is used to encrypt two separate data and that the key in question is linked to two different levels of access rights. For example, an entity that has a key of a given level will access the data of that level. But nothing prevents the same entity from trying to access other data, associated with higher levels of law, with this same cie, and why not, even if the probability of success is low, to access these other data.

In a particular embodiment, one and only one key is used to perform the sequence of ciphers. According to this particular mode, when an entity requires access to a data item, it indicates a number of successive decryptions to be performed to access this data, and the access step is preceded by a verification step of the indicated number. , the decryption of a data being performed if the number is correct. By limiting the number of decryptions made, the method remains reliable even if only one key is used during the succession of encryption.

The invention also relates to the electronic module and the entity participating in the method.

The module includes

storage means capable of storing at least one datum to which is assigned a respective access right level that must be possessed by said entity to access this datum;

- Verification means able to verify that an entity wishing access to said at least one data has a sufficient level of law.

- Access authorization means adapted to allow access to said at least one data.

As has been seen previously in one embodiment, said at least one piece of data is encrypted by means of an encryption key; the authorization means are able to authorize access to the said at least one data item provided that the entity that accesses the said at least one piece of data has the decryption key capable of decrypting the result of the encryption of the said at least one piece of data. given. As seen previously in one embodiment, the module can store at least two data (DT1, DT2, ..., DTi-H, DTi, ... DTn) associated with a level of access rights respective ones (N1, N2, N3, ..... Ni + 1, Ni, ..., Nn), said levels satisfying the following mathematical relationship N1 cr N2c:.,. c Ni + 1 c Nicz .., cNn (n≥1), each level (N1, N2, N3, ..... Ni-M, Ni, ..., Nn) being associated with at least one key of respective encryption

(K1, (K1.K2), ..., (K1, ..., Ki + 1), (K1 Ki), ... (K1 Kn) In this particular mode, said module comprises

encryption means capable of encrypting a datum DTi associated with a level of right Ni by performing a succession of encryption according to the following relationship

R = _K E [DTi] for the encryption of the order data i

and the following recursive relation R ₁ = E, [DT ₁ ^ R,],

- R ₍ being the result of the encryption of at least the data DT,;

- R, _, being the result of the encryption of at least the set including the data DT _M and the result of the previous encryption performed R _; ;

- E _j1 ,, being an encryption function, the index indicating the key used for encryption;

decryption means adapted to perform a succession of decryptions of the preceding relationships by means of said at least one encryption key associated with the level Ni to access said at least one data item DTi, DT _M , .... DTl As has been seen previously in one embodiment, the module comprises means for limiting the decryption number to the number of key (s) associated with the level of right of an entity.

The module also includes

reception means able to receive, from an entity, the use order of Ia said at least one key associated with a level for performing the decryption of a data,

means for verifying the order of use,

means capable of activating decryption if the order is correct. As we saw earlier, the module also includes

means for receiving a decryption number to be produced

means capable of verifying the number received,

means capable of activating decryption if the number is correct.

The entity comprises storage means capable of storing at least one access right level associated with a respective datum.

In a particular mode, we have seen that a level is represented by at least one encryption key. According to this mode, the entity includes

storage means capable of storing at least one key associated with a given level of entitlement,

means for transmitting said at least one key.

In a particular mode, the entity comprises indicating means able to indicate the order of use of the keys.

Finally, the subject of the invention is the computer program that can be implemented on an electronic module as previously, said program comprising code instructions which, when the program is executed, perform an access authorization step. to at least one datum according to the level of access rights that the requesting entity has access to the at least one data item.

The invention will be better understood on reading the description which follows, given by way of example and with reference to the accompanying drawings. In these figures, for the sake of simplification of the description, the same elements bear the same references.

The figures: Figure 1 is a view of a computer system on ieque! may apply the invention.

FIG. 2 illustrates an example of a recurrence in the computation of the encryption of a data item.

FIGS. 3, 4 and 5 are algorithms illustrating the encryption and decryption steps with reference to the embodiment of FIG. 2.

FIG. 6 is an example illustrating a generalization of the example illustrated in FIG. 2.

Detailed description of an exemplary embodiment illustrating the invention

FIG. 1 represents a SYS computer system in which the invention can be implemented.

The system includes a memory module storing data and at least one entity capable of requesting access to the data.

In our exemplary embodiment, the memory module is a smart card (CP). This card includes a microcontroller including in particular a microprocessor, memory means MElvï for storing data, encryption means and decryption CHF data. io

For the sake of simplification of the description, these encryption and decryption means CHF bear the same reference.

In our exemplary embodiment, an entity accesses the data stored on the card by means of a respective card reader LCT1 and LCT2. Communication between the CP card and a reader is performed, for example, by means of electrical contacts (not shown in the figures).

In our example, an entity corresponds to a natural or legal person wishing to access the contents of the CP card. This person can be an administration, a merchant, etc. In the following description, it will be assumed that the entity designates both a person but also the data processing device (not shown in the figures) with which the person accesses the data stored on the card. This device is for example a computer.

In FIG. 2, for the purpose of simplifying the disclosure of the invention, we will initially limit to three the number of data stored on the card. Consider in this example that two entities, a first entity ENT1 and a second entity ENT2, wish to access the content of at least one piece of data.

According to the invention, access to data is authorized if the entity wishing to access the data stored on the card has a sufficient level of access rights. For this purpose, the card comprises verification means able to verify that an entity wishing access to said at least one item of data has a sufficient level of entitlement, and access authorization means able to authorize access to said at least one datum.

In order to restrict access to a part of the data DT1-DT3, in our example, each data is encrypted by means of at least one encryption key. Let's consider that entities ENT1 and ENT2 have a respective level of access rights N1 and N2. In our exemplary embodiment, this level of access right is represented by at least one encryption key. 1]

A right of access to a data therefore requires the possession of at least one encryption key. If so, the authorization means authorize access.

The encryption method can take several forms illustrated by the following two variants.

According to a first variant of the encryption method, each piece of data may be encrypted, by means of encryption means, by a respective encryption key. For example, if each data DT1-DT3 is associated with a respective level of access rights N1, N2, N3, an entity wishing to access one of the data must have the key associated with the corresponding access level. For example, if DT1 is encrypted with a key K1, if DT2 is encrypted with a key K2, if DT3 is encrypted with a key K3, and an entity wishes to access all or part of the data DT1, DT2, DT3, this The entity must have the key K1, K2 or K3 depending on the data it wishes to access.

According to a second variant of the decryption method, when at least two levels, for example N1 and N2, are such that one is a subset of the other (N1 c N2), meaning that the level N2 provides more than rights that the level N1, the encryption method is advantageously that presented in the following description with reference to Figures 2 and 3.

Note that your encryption means are not necessarily located on the map. Indeed, an external device (not shown) to the card can perform encryption. On the other hand, the result of the encryption is necessarily stored on the card.

In our example, the decryption means are on the card for practical reasons and security reasons.

FIG. 2 illustrates an example of a method illustrating the management of data access DT1-DT3. In this example, it is assumed that the three data DT1-DT3 are associated with three respective levels of law N1-N3 such that N3 is a subset of N2 which itself is a subset of N1. The three levels N1, N2, N3 therefore verify the following inclusion relation:

N1 c N2 c N3, meaning that level N3 provides more rights than level N2 and that level N2 provides more rights than level N1.

The operator c designates the inclusion operator.

Note that in the present description, the term "data" is not limited to a single value. On the contrary, the term "given" may include a plurality of information. For example, an "identity" data item may include, surname, first name, sex, date of birth, etc.

The different steps of the process are illustrated with reference to FIGS. 3, 4 and 5.

The data encryption comprises a first preliminary step ET1, in which each data DT1-DT3 is associated with a level of access rights. The entity comprises storage means capable of storing at least one access right level associated with a respective datum. In our exemplary embodiment, this first identification step is performed prior to the loading of the data in the card by an authorized person, for example the owner of the card or an administration.

In our example, an entitlement level is represented by at least one encryption key. In the remainder of the description, for purposes of simplifying the description, it will be assumed that Ki (i≈1, n) designates both an encryption key and the respective decryption key. Thus, with this terminology, Kn makes it possible to encrypt data and to decipher the encrypted data that results from this encryption.

In our example, the data DT1 is accessible provided that it has a level of access N1, and thus to be in possession of (a key of encryption Kl

DT2 data is accessible provided to have access level N2, and therefore to be in possession of encryption keys K1 and K2; the data DT3 is accessible provided to have an access level N3, and therefore to be in possession of the encryption keys K1, K2, K3.

In a second step ET2, the data DT1-DT3 are encrypted. In our exemplary embodiment, this second encryption step is performed either by an organization authorized to write data on the card or by means of a program stored on the card able to take into account for each data the right level of the data. access and perform an encryption according to the following encryption phases PH 1 to PH5.

During a first preliminary phase PH1, one identifies among the data one (s) associated (s) with the higher level of right; in our example, the data DT3 is associated with the highest level N3.

During a second phase PH2, in our example, the data DT3 being the one that requires the highest access level, this data DT3 is encrypted by means of the key K3. The result of encryption is

R ₃ = E _n (DT ₃ )

During a third phase PH3, one identifies among the remaining data DT2 and DT1, the data associated with the level of law directly below the level N3. In our example, DT2 corresponds to this data.

During a fourth phase PH4, the data item DT2 is encrypted; encryption consists in encrypting both the data DT2 associated with the level access K2 and the result of the previous encryption R ₃ operated at the second phase PH2. The result R K2 of this encryption is

R ₂ = E ^ <DT2, R ₃ )

During a fifth phase PH5, one identifies among the remaining data the data associated with the level of law directly lower than the level N2. In our example, DT1 corresponds to this datum. The encryption of DT1 consists in encrypting both the data DT1 and the result of the previous encryption R ₂ operated at the fourth phase PH4 by the K2 cié. The result R ₁ of this encryption is

R, = E ^ ₁ (DTI, R ₂ ).

At this stage of the process, the data DT1-DT3 are encrypted and stored on the card.

According to the invention, the encrypted data is accessible only by the entities that have the required levels of entitlement.

In a third step ET3, the encrypted data is decrypted on request of an entity.

In order to illustrate the decryption phases, let us now consider that the two entities ENT1 and ENT2, for example an administration and a merchant, respectively, wish to access the data stored on the card. Consider that the first entity at a level of law N3 reads allowing access to the set of data DT1-DT3 and that the second entity has a level of law N1 limited to the data DT1 which corresponds, for example, to data of d1. identity as found on a traditional paper ID card. These identity data are used for example by a merchant to prove the identity of the customer when he makes, for example, a payment by check.

In our example, the first entity ENT1 is in possession of the three decryption keys K1, K2, K3 to access all the data. DT1-DT3 and the second entity ENT2 is in possession of a single key, namely K1 associated DT1 data.

Another example might be to store no key on an entity. The access of an entity to the content of the card would then consist of an authentication of the entity by the card, for example by means of a biometric fingerprint. This authentication allows the card to know the level of access rights associated with this entity. In this example, the fact that entities do not know the keys reduces the risk of fraud.

In our example embodiment, the entity is aware of its level of access rights and associated keys at this level. In our example, the decryption method relating to the first entity ENT1 comprises several phases PH6 to PH10. Decryption is performed by decryption means. These different decryption phases follow, directly or indirectly, the encryption process described above.

During a sixth phase PH6, in our example, the card CP is inserted in the reader LCT1; and the first entity ENT 1 requires access to the data stored on the card.

During a seventh phase PH7, the request initiated by the first entity is transmitted to the card. In our exemplary embodiment, the request includes an identifier of the first entity. In our example, the identifier is represented by the encryption keys K1-K3 corresponding to this level of entitlement that the first entity possesses. The request optionally includes the name of the data DT1-DT3 that the first entity wishes to access; nevertheless, the name of the data is not necessary because the keys alone would make it possible to identify the data to which the first entity will have access.

Note that this phase PH7 is not necessary when the entity stores no encryption key and all the encryption keys are known only to the card. In this case, authentication is sufficient to obtain the identity of the entity and deduce its level of access rights. During an eighth PH8 phase, possibly after having authenticated the first entity and according to the level of right associated with this first entity, the card realizes a decryption of the data corresponding to this level of right by means of the keys K1 to K3.

Preferably, in our exemplary embodiment, the number of decryption operations to be performed is limited to the number of keys associated with the level of right of an entity. Thus, in our example, since the first entity is associated with the level N3 and at this level corresponds to three keys, the number of decryption operations is limited to three for the first entity.

During a ninth phase PH9, one of the three keys K1 ~ K3 is selected from that used for the encryption of DT1, namely K1. Decryption will then begin with this key.

At a tenth PH10, the card decrypts the result obtained during the fifth phase defined above, namely:

R ₁ = E _Jf1 (DTI, R ₂ ) with the decryption key K1 and obtains both the data DT1 and the result of the encryption by the key K2 namely R ₂ ≈ E _O (DT2, R ₃ ). At this stage, the first entity ENT1 can read the data DT1 and the result R ₂ , but still has no access to DT2 or DT3.

Then, it is selected from the three keys K1-K3 that used for the encryption of DT2, namely K2, A second decryption operation is performed and consists in decrypting R ₂ with the key K2. The result of this decryption provides the data DT2 and R ₃ = E _Ki result (DT _3).

At this point, the first entity ENT1 can read the data DT1 and DT2, DT3 being in encrypted form. the first entity ENT1 holds a third and last key, namely K3; In our example, a last decryption operation is performed with K3. The result of this operation is to get DT3. At this stage the first entity ENT1 has access to the three data DT1 to DT3.

If the entity is the second entity ENT2, the decryption method is different. Indeed, as we indicated previously, the merchant is associated with a reduced level of access right N1 level N1 which corresponds to a single key namely K1.

When the second entity ENT2 accesses the data stored on the card, the decryption phases differ:

The sixth phase PH6 is the same as that defined previously.

During a seventh phase PH7, the request initiated by the second entity ENT2 is transmitted to the card. In our exemplary embodiment, the request comprises an identifier of the second entity. In our example, the identifier is represented by the encryption key K1 corresponding to the right level N1. The request optionally includes the name of the data DT1 that the second entity wishes to access; however, the name of the data is not necessary because key K1 alone would identify the data to which the second entity ENT2 will have access.

The eighth PH8 phase remains unchanged.

The ninth PH9 phase is deleted because it no longer needs to be.

During the tenth phase PH10, the card decrypts the result obtained during the fifth phase defined above, namely:

R ₁ = E _J0 (DTI, R ₂ ), with the decryption key K1. The result of this decryption makes it possible to obtain the data DT1 and the encrypted data R, the result of the fourth phase defined above.

The second entity ENT2 has no other rights. The decryption phases are completed. Unlike the encryption phases relating to the first entity, the following phases do not take place. Preferably, as indicated above, the number of decryption operations to be performed is limited to the number of ciues associated with the entity's level of entitlement. Thus, for the second entity ENT2, the number of decryption operations is limited to one.

For this purpose, the card comprises means adapted to count for a given access right level the number of associated keys, for example by means of a counter; and to achieve a decryption number equal to the number of keys in question.

The card could also include means capable of inhibiting the decryption function when the limit in the number of decryptions is reached.

More generally, with reference to FIG. 6, consider that the card stores n data (DT1 _S DT2, .... DTi + 1, DTi, ... DTn), n being any integer. Consider that these n data are associated with a respective level of law (N1, N2, N3, NH-1, Ni, ..., Nn). Let us consider that the different levels satisfy the following mathematical relation N1 c N2c ... c: Ni + 1 c Htc ... c Nn (n ≥ i) in the sense that a level Ni-1 includes in a level Ni a minus of law that this level Ni (i being an integer greater than 1). Consider that each level (N1, N2, N3, ...., Ni + 1, Ni, ..., Nn) is associated with at least one respective encryption key (K1, (K1.K2), ... , (K1, ..., Ki + 1) ₁ (K1, ..., Ki), ... (K1, ..., Ki, ..., Kn).

The encryption of a datum DTi associated with a right level Ni comprises a succession of ciphers according to the following relationship

R ₁ = E _J0 [DTi) for the encryption of the order data i

and the following recurrence relation R _M = E, [DT ^ R ₁ ], - R, being the result of the encryption of at least the data DT,;

- R _M being the result of the encryption of at least the set including the data DT, _, and the result of the previous encryption performed R ₍ ;

- E _p being an encryption function, the index K, indicating the cie used for encryption;

Note that the encryption function E _K) can be different at each encryption phase.

The two preceding relationships include parameters in square brackets, namely [DTi] and [DTi, R _{1 + 1} ]. In our example, the brackets indicate the relevant data taken into account during the ciphering namely respectively the data DTi and the set related to the recurrence (DTi, Ri). For purposes of simplification of the disclosure of the invention, irrelevant data, for example constant data are not indicated in these brackets. Another writing of previous relationships could be:

R = E ^ [ϋTi, Ci] for the encryption of the order data i

and the following recurrence relation

R _H = E, JDI:

C, and C _1-1 designating constant data taken into account to obtain the result Ri and R, _, respectively.

Note that a key Ki may comprise a set of keys w1 to wj (j being any integer).

In this general case, the step of accessing a data item DTi comprises a succession of decryptions of the previous relationships. This step of accessing the data DT1 to DTi requires the possession of the key Ki of order i as well as the keys (K1, K2, K3, ..., K _1-1 ) allowing access to the data associated with the levels lower law (N 1, ..., Ni-1) at the Ni level. Access to the data of order "i" DTi consists of a plurality of successive decryptions of the results obtained during the encryption, starting with the result R1 obtained by the key K1, and thus follows to R, obtained by the respective key Ki.

It has been seen previously, with reference to FIG. 2, that the number of decryption operations to be performed is limited to the number of keys associated with the level of right of an entity. For this purpose, limiting means stored on the card have the function of limiting the number of decryption (s) to the number of key (s) associated with the level of right of an entity.

According to a first variant, when an entity wishes to access a piece of data, this entity indicates the order of use of the said at least one key associated with a level for performing a decryption. For example, access to data DTi requires possession of the keys (Ki,..., K1) and knowledge of the order of use of the keys. In our example, the order of use of the keys for decryption is the reverse order of the one used for encryption. For this purpose, the entity comprises storage means capable of storing at least one key associated with a given level of law means for transmitting said at least one key. the map includes

reception means capable of receiving, from an entity, the order of use of the said at least one key associated with a level for carrying out the decryption of a data item,

means for verifying the order of use,

means capable of activating decryption if the order is correct.

Correlatively, in our example, the entity comprises indicating means able to indicate the order of use of the keys.

Seion a second variant, one and only one key is used during the succession of ciphers. According to this particular mode, when entity requires access to data, this entity indicates a decryption number (s) to be made to access this data, the access step being preceded by a verification step of the indicated number, the decryption of a given that the number indicated is correct. For example, in the example illustrating FIG. 2, the first entity indicates to the card that three successive decryptions must be made in order to have access to the data D1 to D3. The card checks this number and allows access if the number is correct. For this, the card stores beforehand a table including, for at least one datum, the number of decryptions to perform. For this purpose, the module includes

means for receiving a number of decryptions to be made,

- verification means able to verify the number received,

means capable of activating decryption if the number is correct.

It should be noted that the different verification means may be included in one and only verification means, or may be separated from one another.

In a particular embodiment, the first variant is applied to a subset of data and the second variant is applied to another subset of data.

In order to improve the security of information during exchanges between the card and the reader, the data is encrypted by means of an encryption algorithm. In our example, the algorithm is symmetrical. With this type of algorithm, the longer the length (number of bits) of the secret code is greater the algorithm is resistant to attacks. The current trend is therefore to increase the length. However, increasing the size of the keys has the effect of increasing the time required for encryption and decryption of data. To overcome this drawback, a solution for improving this resistance of the keys is as follows: the card and the reader stores the same table with the same key values. In this array, to a key corresponds a respective index. In our example, the transmission method is as follows:

- the card randomly calculates an index;

the card encrypts the data to be transmitted with ease associated with this index;

the card transmits the encrypted data and the calculated index to the entity that initiated access to this data;

the entity receives the encrypted data and ['index;

the entity deduces the associated key by virtue of the received index;

the entity decrypts the encrypted data by means of the deduced key.

In our example, the message transmitted from the card to the entity advantageously comprises information, for example a bit, indicating that the message includes encrypted data and that its access will require decryption.

Advantageously, the organization of the memory is based on a partition of the memory in at least one folder. In our example of realization, 4 files are created namely: an official file, a professional file, a commercial file a personal file. In our example, a folder includes at least one application.

The number of files can be more or less important; the user can, at will, add folders or applications; he can also delete it. Consider, for example, the "official" file. Let's consider that this "official" folder contains an APP1 application that includes driver license information. The application APP1 includes for this purpose several fields associated with a respective level of law. For example, consider that the APP1 application comprises the fields appearing in the table represented below and that each field is associated with a respective level of law N1, N2, or N3 satisfying the following inclusion relation: N1 c N2c N3

In this example, the DT1 data is

Last name

First

Validity date

Access to this data DT1 requires the possession of the key K1. In the same way, the DT2 data is

Address

City

Photo holder

Access to this data DT2 requires the possession of keys K2 and K1. In the same way, the data DT3 is Birth date

Place of birth

Native country

Seal of authority

Date of issue

Access to this data DT3 requires the possession of the keys K1, K2 and

K3.

Thus, an access right level N3 will allow the reading of the data DT1, DT2 and DT3 by means of the keys K1, K2 and K3, an access level N2 will allow the reading of DT1 and DT2 by means of KI and K2; and lastly the level of access right N1 will allow the reading of DT1 by means of the key K1.

Note that the invention relates to an access management method of an entity to at least one piece of data stored on a memory module. The term "an entity" does not limit the use of the invention to a single entity; on the contrary, the invention applies to all entities able to communicate with the card.

Claims

claims

1. Access management method of an entity (ENT1, ENT2), at least one datum (DT1, DT2, ..., DTi + 1, DTi ₁ ... DTn) stored on a memory module (CP ), characterized

the access is preceded by a preceding assignment step able to attribute to said at least one datum a level of access right that must be possessed by said entity to access this datum;

and in that it comprises an access step in which the entity accesses said at least one item provided that it has a sufficient level of access rights.

2. Method according to claim 1, characterized in that the assigning step consists in encrypting said at least one piece of data by means of an encryption key, and in that during the access step, the entity accesses said at least one item provided that it has the decryption key capable of decrypting the result of the encryption of said at least one piece of data,

3. Method according to claim 2, characterized in that, if there are at least two data (DT1, DT2, ..., DTi + 1, DTi, ... DTn) associated with a level of access rights respective ones (N1, N2, N3, ..... NH-1, Ni, .... Nn), said levels satisfying the following mathematical relation N1 c N2c.,. c Ni + 1 cNic ... cNn (n≥ I), each level (N1, N2, N3, ...., Ni + 1, Ni, ..., Nn) being associated with at least one encryption key respective (K1 (K1, K2), ..., (K1, ..., Ki + 1), (K1 _t ..., K), ... (K1 Kn), in that encryption of Ie a data item DTi associated with a level of right Ni comprises a succession of ciphers according to the following relation

R ₍ = E _fi [DTi] for the encryption of the order data

And the following recurrence relation

R, _, = E ^ ₁ [DT ₁ ^ R ₁ ], R, being the result of the encryption of at least the DT data;

R, being the result of the encryption of at least the set including the data DT _M and the result of the preceding realized encryption R,

- E ^, being an encryption function, the index indicating the key used for encryption; and in that the step of accessing said at least one data DTi, DT, _,,

..., DT1 comprises a succession of decryptions of the previous relationships by means of said at least one associated encryption key at the Nt level.

4. Method according to claim 3, characterized in that the number of decryptions made successively is limited to the number of keys associated with the level of access right.

5. Method according to claim 3 or 4, characterized in that the entity indicates an order of use of said at least one key associated with a level, in that the access step is preceded by a step verification of the order of use indicated, and in that the decryption of data is carried out if the order is correct.

6. Method according to claim 3, characterized in that if a single key is used to carry out the succession of ciphers, the entity indicates a number of successive decryptions to be performed to access a datum, and in that the step d access is preceded by a verification step of the indicated number, and in that the decryption of a data is performed if the number is correct.

7. Electronic module capable of communicating with an entity through a reader, said module storing at least one datum, characterized in that it comprises storage means capable of storing at least one datum to which is assigned a respective access right level that must be possessed by said entity to access this datum;

verification means capable of verifying that an entity wishing access to said at least one item of data has a sufficient level of entitlement,

- Access authorization means adapted to allow access to said at least one data.

8. Module according to claim 7, characterized in that said at least one piece of data is encrypted by means of an encryption key, and in that the authorization means are able to authorize access to said at least one piece of data. provided that the entity accessing said at least one piece of data has the decryption key capable of decrypting the result of the encryption of said at least one piece of data,

9. Electronic module according to claim 8, characterized in that it stores at least two data (DT1, DT2, .. ,, DTi + 1, DTi, ... DTn) associated with a respective level of access right (N1, N2, N3, ..... Ni + 1, Ni _1, ..., Nn), said levels satisfying the following mathematical relationship c N2E N1 ... Ni + c 1 c c Nic ... Nn ( n≥i), each level (N1, N2, N3, ...., Ni + 1, Ni, ..., Nn) being associated with at least one respective encryption key

(K1, (K1.K2), ..., (K1, ..., Ki + 1), (K1 Ki), ... (K1 Kn), said module comprising

R ₁ = E _Kl [DTi] for the encryption of the order data item

and the following recurrence relation

- R ₁ being the result of the encryption of at least the data DT,; - R _{^ j} being the result of the encryption of at least the set including the data DT, _, and the result of the previous realized encryption R,;

- E _Kl being an encryption function, the index K _; indicating the key used for encryption;

decryption means capable of realizing a succession of decryptions of the preceding relationships by means of said at least one encryption key associated with the level Ni in order to access said at least one data item DTi, DT, _, DT1.

10. Module according to claim 9, characterized in that it comprises limiting means capable of limiting the decryption number to the number of key (s) associated with the level of right of an entity.

11. Module according to claims 9 or 10, characterized in that it comprises

means for verifying the order of use,

means capable of activating decryption if the order is correct.

12. Module according to claims 9, characterized in that it comprises

means for receiving a number of decryptions to be made,

means capable of verifying the number received,

means capable of activating decryption if the number is correct.

13. Entity able to communicate with an electronic module through a reader, said module being able to store at least one datum (DT1, DT2, ..., DTi + 1, DTi, ... DTn), characterized in that it includes means of storage capable of storing at least one access right level associated with a respective data item.

An entity according to claim 13, characterized in that a level is represented by at least one encryption key.

15. Entity according to claim 13, characterized in that it comprises

means for transmitting said at least one key.

16. Entity according to claims 14 or 15, characterized in that it comprises indicating means adapted to indicate the order of use of the keys.

17. A computer program adapted to be implemented on an electronic module as defined in claim 7, said program comprising code instructions which, when the program is executed performs a step of authorizing access to at least data according to the level of access rights owned by the entity requesting access to said at least one data item.