WO2013060539A1

WO2013060539A1 - Method and system for establishing a relationship between sets of information about a single person

Info

Publication number: WO2013060539A1
Application number: PCT/EP2012/068789
Authority: WO
Inventors: Patrick Guerin
Original assignee: Celtipharm
Priority date: 2011-10-28
Filing date: 2012-09-24
Publication date: 2013-05-02
Also published as: FR2982104A1; EP2772003A1; FR2982104B1

Abstract

The invention relates to a method for establishing a relationship between sets of information about a single person from a plurality of sets of information about a plurality of persons, each information set being associated with a personal identification number imprint (DH(NIP)) from a personal identification number (NIP), characterized in that the method comprises the following steps in the or each information device (Ei) hosting databases in which said information sets are stored: ciphering (3) each imprint (DH(NIPj)) with a so-called first key (lki) depending on the personal identification number (NIPj) from which the imprint originates in order to obtain a first ciphered imprint (C(lki;DH(NIPj)); ciphering (4) the first key (lki) with another so-called second key (Pwi) in order to obtained a ciphered key (C(PWi, lki)); transmitting both the ciphered imprint (C(lki;DH(NIPj)) and the ciphered key (C(PWi, lki)) to the central device (Ec); wherein the method further comprises the following steps in the central device (Ec) dedicated to the establishment of the relationship: deciphering (5) each of the ciphered keys (C(PWi, lki)) by means of the second key (Pwi) in order to obtain the first key (lki); deciphering (6) each ciphered imprint (C(lki;DH(NIPj)) by means of the first key (lki) thus deciphered in order to obtain the imprint (DH(NIPj) of each information set; and established a relationship between the two information sets when the imprints (DH(NIPj) associated thereto correspond.

Description

Method and system for linking together sets of information relating to the same person

The present invention relates to a method of linking together sets of information relating to the same person. It also relates to information and central equipment provided for the implementation of this method and a system for chaining together sets of information stored in databases that uses this linking method and a computer program.

It is increasingly common to want to link (cross) between them information relating to the same person in order to identify trends of consumption or use and other statistics and, in particular, in the social or social field. health.

It is not uncommon, especially in the field of health, that patient information sets are collected and stored in databases hosted by multiple remote information facilities and that related information sets relating to the same person to know, for example, his consumption habits, to make follow-ups of treatments, or to calculate statistics concerning an epidemiological study carried out by several institutions, etc. The linking of these sets of information allows the chaining of databases that allows to query these databases to retrieve all information related to the same person.

Linking these sets of information between them requires that these sets be identified as relating to the same person. The person identifier number (PIN or PIN for Personal Identification Number) is usually used for this purpose. Thus, the person identifier numbers associated with the sets of information collected by the different remote devices are compared with each other and, as soon as two numbers are identical, the associated sets are related because they are related to the same person.

This type of method of linking sets of information can not be implemented as simply in practice because it is not possible to leave any equipment the possibility, on the one hand, to be able to put in relation confidential information relating to the same person and, secondly, to go back to the identity of that person.

In other words, the problem solved by the present invention is to define a method which makes it possible to relate together sets of confidential information of a person, in particular for purposes of statistical exploitation while preserving the anonymity of these people.

For this purpose, there are known methods that combine hash functions and key encryption for medical applications (Quantin C, Bouzelat H., Allaert FA., Benhamiche AM., Faivre J., Dusserre L. Automatic record hash coding and linkage for epidemiological follow-up data confidentiality.

Med 1998; 37: 271-7) or again (Blakely T., Woodward A., Salmond C.) Aust N Z J Public Health

2000; 24: 92-5) or (Churches T., Christen P. Some Methods for Blindfolded Record Linkage, BMC Med Inform Decis Mak 2004, 28: 4-9). Subsequently, the term encryption is synonymous with the term encryption also used in the literature.

In these methods, the hash function transforms the person ID number into a single, reduced-length hash value called a fingerprint.

This fingerprint serves to quickly identify a person without being able to go back to his ID number and thus to his identity. This fingerprint is often also called anonymous ID number. A hash function is defined so that the probability that two person ID numbers have the same fingerprint is very small.

In some of these methods, the hash function is not applied directly to the person identifier number but to a code formed by the concatenation of a prefix (sometimes called a hash key) and this identifier number. belongs to nobody. This solution avoids any so-called dictionary attack. In fact, a first piece of equipment, which has collected sets of information relating to a person, obtains, from a prefix, a particular code for each person whose sets of information have been collected. On the other hand, a second device, which is not aware of this prefix, can not regenerate this code from the identifier number of this person because he does not know this prefix. This second equipment can not therefore obtain a fingerprint relative to an ID number of a person that is identical to that generated by the first equipment and can not go back to the identity of this person.

This type of method therefore imposes the use by the information equipment of the same prefix each time the sets of information collected by these information equipment must be put in relation to each other. This constraint goes against the limitation of fraudulent access by remote information equipment to the collection of information sets because it is sufficient for this information equipment to know this prefix to access (by dictionary attack) sets of information collected by all information facilities that use this prefix.

Hence the use in these methods of a key encryption function that limits access to the person identifier numbers thus anonymized by hashing. This encryption function allows equipment that has collected sets of information to be able to protect their access to any other remote device by keeping the encryption key secret. Access is thus restricted even to equipment that uses the same encryption key. This encryption function can also be used to secure the transmissions between equipments since, for example, a person identification number must be transmitted by a device, for example a collector, to another equipment, for example central. Again access to fingerprints of person ID numbers is limited to equipment that knows the encryption key used.

These methods of linking sets of information use, most often, a central piece of equipment which requests the information equipment which has collected these sets of information to send it the encrypted fingerprints of the persons for whom they are storing data. sets of information. Each piece of information equipment uses a particular encryption key that allows this equipment to limit access to the sets of information that it stores. The central equipment is then able to decrypt the encrypted prints that are issued by the information equipment because it knows the decryption keys relating to each of these collecting equipment. The central equipment can then relate decrypted fingerprints but is the only one to be able to do so because the information equipment knows only these decryption keys.

To solve the above technical problem, the present invention relates to a method of relating together sets of information relating to the same person among a plurality of sets of information relating to several persons, each set of information associated with a person ID number imprint from a person ID number.

According to the invention, this method comprises the following steps performed in the or each piece of information equipment hosting the databases in which the said sets of information are stored:

encrypting each fingerprint with a key, called the first key, which depends on the person identification number from which the fingerprint is issued, in order to obtain an encrypted fingerprint,

encrypting the first key with another key, called the second key, in order to obtain an encrypted key,

transmission to said central equipment on the one hand, the encrypted footprint and, on the other hand, the encrypted key,

as well as the following steps performed in said central equipment dedicated to the connection:

decryption of each of the encrypted keys by means of the second key in order to obtain the first key, and

decryption of each encrypted fingerprint by means of the first key thus deciphered in order to obtain said fingerprint of each set of information, - Linking two sets of information when the fingerprints associated with them correspond.

Double encryption (of the fingerprint and the first key) makes it possible to increase the robustness of the process against possible dictionary attacks because only the knowledge of these two keys (first and second) makes it possible to go back to the fingerprint of person ID number. This means that only duly authorized equipment can access the fingerprint used to link sets of information. Thus, from the knowledge of these two keys, the process finds fingerprints and uses them to link sets of information, for example for statistical purposes.

According to one embodiment, the first key is the result of the application of a hash function on a person identifier number fingerprint.

This embodiment further increases the security of access to the person ID numbers because it introduces a second hashing step in the method that is related to the person ID number.

In addition, the hash function used for these two hash functions is preferably the same which facilitates the implementation of the method compared to the use of different hashing methods, on the one hand, to "anonymize" the number of person identifier and, secondly, to "obtain the first key from a person ID number.

According to one embodiment, a fingerprint associated with a set of information is the result of the application of a hash function on a code obtained by concatenation of a prefix followed by a person identifier number.

According to one embodiment, the first key is a public key of an asymmetric encryption method.

This embodiment makes it possible to have different keys for encryption and decryption, which increases the communication security of the encryption keys between devices.

The invention also relates to a computer program, which can be stored on a medium and / or downloaded from a communication network, in order to be read by a computer system or a processor. This computer program includes instructions for implementing either the steps of the aforementioned method that are implemented in information equipment, or the process steps that are implemented in a central equipment, when said program is executed by the computer system or the processor. The invention also relates to storage means comprising such a computer program.

According to its material aspects, the present invention relates to information equipment which comprises means for implementing the steps of encryption and transmission of the method and a center equipment which comprises means for implementing the steps of decryption and linking the process.

Finally, it also relates to a system for chaining sets of information that include these different devices.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being given in relation to the attached drawings, among which:

Fig. 1 is a diagram of the steps of the method of relating together sets of information relating to the same person according to the present invention.

Fig. 2 is a diagram illustrating a system for chaining sets of information relating to persons using the method of FIG. 1.

Fig. 3 schematically illustrates the architecture of the communications equipment implementing the method of FIG. 1.

In FIG. 1 is schematically represented a diagram of the steps of the method according to the invention of linking together sets of information relating to the same person among a plurality of sets of information relating to several people. These steps are implemented, on the one hand, in an information equipment Ei and, on the other hand, in a central equipment Ec. Each information device is intended to store a set of information that is associated with a fingerprint issued from a PIN number. Two sets of information are related, according to the method, when the fingerprints associated with them correspond or even are identical. This association is performed in the central equipment Ec after the one has received from at least one equipment Ei an encrypted associated fingerprint and a first key encrypted by a second key, as explained below.

According to one embodiment, a fingerprint of person ID numbers, also called simply fingerprint, associated with a set information, and noted DH (NIP), is the result of applying a hash function on a PIN person ID number.

According to another embodiment, a DH (NIP) fingerprint is the result of the application of a hash function on a code obtained by concatenation of a prefix followed by a PIN number.

According to a variant of this embodiment, a fingerprint, denoted DH (DH (NIP)), is the result of the application of a hash function on a new code obtained by the concatenation of a new prefix followed by the previous fingerprint DH (NIP).

This variant is particularly effective in limiting the possibility for equipment involved during a statistical analysis of the information collected by different equipment to be able to go up to the anonymized person identification number because only a limited number of equipment can know the first prefix and an even more limited number can know both prefixes.

According to one embodiment, the hash function used implements an algorithm of the SHA (Secure Hash Algorithm) family that can be found for example on the site (http // en.wikipedia.org / wiki / SHA_hash unctions).

The method further includes a step 3 of encrypting each DH (NIP) fingerprint with a key lk. This key lk, called the first key, is obtained in step 2 of the method from the PIN person identifier number from which the DH (NIP) fingerprint is issued or directly from the DH fingerprint (PIN ) as shown in FIG. 1, for example, by applying a hash function.

The method further comprises a step 4 of encrypting the first key lk with another key Pw, said second key.

Steps 3 and 4 are implemented in an information equipment Ei.

The method further comprises, implemented in a central equipment Ec, a decryption step 5, from the encrypted key C (Pw, lk) transmitted by an information device Ei, of the first key with the second key Pw and a decryption step 6, from the transmitted encrypted footprint C (lk; DH (NIP)) by the same information equipment Ei, the identifier number DH (NIP) with the first key lk obtained after decryption in step 5.

The central equipment Ec is in turn designed to implement a step of linking two sets of information when the footprints associated with them correspond or are identical. Fig. 2 is a diagram illustrating a system for chaining sets of information relating to persons using the method of FIG. 1.

Here, two pieces of information El and E2, for example remote, are connected to the same central equipment EC. The equipment El, E2 and EC are provided with means enabling them to bidirectionally exchange information-carrying signals via a wired or non-wired communication network, for example the Internet. Assume that each information equipment E i has collected sets of information relating to J persons identified by their personal identifier numbers NIPj and therefore by their fingerprints DH (NIPj).

The equipment El, respectively E2, knows, beforehand, a first encryption key denoted 1k1, respectively lk2, and a second key Pw1, respectively Pw2. The central equipment EC knows, beforehand, the two keys Pwl and Pw2. On the other hand, the equipment El does not know the key lk2 nor the key Pw2 and in the same way the equipment E2 does not know either the key 1k1 or the key PW1 and this in order to secure the system against dictionary attacks . Two pieces of information Ei can know and use the same key PWi. This is the case, for example in the field of health, where the sets of information of people are collected by two pieces of information for the same epidemiological study for example which is associated with a single specific PWi key. However, even in this case, two devices Ei can never know the encryption key lki used by another remote device.

Once an information equipment Ei has collected its information sets Ei, it transmits to the central equipment EC the associated encrypted footprint C (lki; DH (NIPj)) to each of these sets of information. This encrypted footprint is thus obtained, according to an embodiment of the method explained above, by hashing the PIN number and then encrypting by means of the key lki. Other methods for obtaining the impression are of course possible without departing from the scope of the present application.

The sets of information remain, in turn, stored by the information equipment Ei who collected them. The central equipment EC is then able, for each of these sets of information to decrypt each first key lki received from a second key Pwi, known beforehand, and then decrypt each encrypted footprint C (lki; NIPj)) received from a first key lki thus decrypted and thus obtain the fingerprint DH (NIPj). The central equipment EC is then able to retrieve the fingerprints of person identifier numbers DH (NIPj) which are associated with the different sets of information transmitted by the equipment Ei, to compare these number fingerprints with each other. identifying a person and connecting two sets of information to each other when their associated DH ID (NIPj) fingerprints match or are identical.

The advantage of this method is to allow the chaining of sets of information that are stored in information equipment comprising remote databases and which are related to the same person while ensuring the confidentiality of this information. Each piece of information equipment Ei will store the information sets of each person with a PIN person identifier number and create an associated encrypted fingerprint C (lki; DH (NIPj)) of its own. It is therefore impossible for equipment to decrypt and thus find the person ID numbers and thus find the person who is associated with this information dictionary attack. In addition, the EC central equipment that knows the decryption keys could go back to the identities of the people from the encrypted person ID number fingerprints but could not make the link between these people and the sets of information collected because these Sets of information remain stored on the information equipment Ei which collected them and are therefore not accessible to this central equipment EC.

The methods and systems have been described above using symmetric key encryption methods, i.e. the same key is used for encryption and decryption. These methods make it possible to quickly encrypt the person ID number fingerprints compared to the time taken by asymmetric key encryption methods, ie the so-called private encryption key is different from the encryption key. decryption, called public.

According to one embodiment, the first key lki is a public key of an asymmetric encryption method.

This embodiment makes it possible to have different keys for encryption and decryption, which increases the security of the encryption method because the public key (corresponding to a key Pwi) is then known only equipment Ei which in need to encrypt their fingerprints of person ID numbers. The decryption of the collected information sets that are stored by the different information equipment Ei is then possible only if these devices know the private key that corresponds to the public key Pwi and encrypted person identifier numbers fingerprints received by the EC equipment are then decrypted by this equipment only if he knows this private key.

This embodiment therefore prevents information equipment Ei from being able to exchange decryption keys and thus facilitates access control to these decryption keys compared to the use of secret keys. In addition, since the time to encrypt the person ID numbers is relatively small and the encryption / decryption of these numbers is not a predominant criterion, it is preferable to use this embodiment rather than a symmetric key encryption method.

Fig. 3 schematically illustrates the architecture of information equipment Ei or central equipment implementing the method of FIG. 1.

The communication equipment 300 comprises, connected by a communication bus 306:

a processor, micro-processor, microcontroller (denoted μο) or CPU (Central Processing Unit in English or Central Processing Unit in French) 301;

a random access memory RAM (Random Access Memory in English or Random Access Memory in French) 307;

- a read-only memory (ROM)

Reading Only in French) 302;

possibly a 305 medium storage drive, such as a SD card reader (Secure Digital Card in English or Secured Digital Card in French);

interface means 303 with a communication network, such as for example an Internet-type network; and

possibly, human-machine interface means 304, allowing, for example, to manage a touch screen and / or a set of keys.

The microcontroller 301 is capable of executing instructions loaded into the RAM 307 from the ROM 302, an external memory (not shown), a storage medium, such as an SD card or the like, or a communication network. When the device 300 is turned on, the microcontroller 300 is able to read instructions from RAM 307 and execute them. These instructions form a computer program that causes the implementation by the microcontroller 301 of all or part of the methods described below in relation to FIGS. 1 and 2. All or part of the methods described above in relation to FIGS. 1 and 2 may be implemented in software form by executing a set of instructions by a programmable machine, such as a DSP (Digital Signal Processor in English or Digital Signal Processing Unit in French) or a microcontroller, such as the microcontroller 301, or be implemented in hardware form by a machine or a dedicated component, such as an FPGA (Field-Programmable Gate Array in English or Programmable Gate Matrix on Field in French) or an ASIC (Application-Specific Integrated Circuit in English or Integrated Circuit Specific to an Application in French).

Implemented in an information equipment Ei, the microcontrollers 301 and the RAMs 307 and ROM 302 cooperate with each other to form encryption means of a fingerprint ID of a person identifier DH (NIP) with a key lk, and to form encryption means of the first key lk with another key Pw. These encryption means are required for the implementation of the method by the communication equipment 300.

Implemented in a central equipment Ec, the microcontrollers 301 and the RAMs 307 and ROM 302 cooperate with each other to form means for decrypting a first key which depends on a fingerprint of the person identification number with another key, and to form means for decrypting an identifier number fingerprint with the first key thus decrypted. These encryption means are required for the implementation of the method by the communication equipment 300.

According to one embodiment, the microcontrollers 301 and the RAMs 307 and ROMs 302 also cooperate with each other to form means for connecting sets of information relating to the same person when the associated person ID numbers are associated. to each of these sets are identical.

Claims

1) A method of relating together sets of information relating to the same person among a plurality of sets of information relating to several persons, each set of information being associated with a fingerprint of the identifier number of person (DH (PIN))) derived from a person identification number (PIN), characterized in that it comprises

the following steps performed in the or each piece of information equipment (Ei) hosting the databases in which said sets of information are stored:

- encryption (3) of each fingerprint (DH (NIPj)) with a key (lki), said first key, which depends on the person identifier number (NIPj) from which the fingerprint is issued, in order to obtain an encrypted footprint (C (lki; DH (NIPj)),

encrypting (4) the first key (lki) with another key (Pwi), called the second key, in order to obtain an encrypted key (C (PWi, lki)),

transmission to said central equipment (Ec) on the one hand, of the encrypted footprint (C (lki; DH (NIPj)) and, on the other hand, of the encrypted key (C (PWi, lki)),

as well as the following steps performed in said central equipment (Ec) dedicated to the connection:

decrypting (5) each of the encrypted keys (C (PWi, lki)) by means of the second key (PWi) in order to obtain the first key (lki), and

decrypting (6) each encrypted fingerprint (C (1ki; DH (NIPj)) by means of the first key (lki) thus decrypted in order to obtain said fingerprint (DH (NIPj) of each set of information,

- Linking two sets of information when the footprints (DH (NIPj) associated with them correspond.

2) The method of claim 1, wherein each fingerprint (DH (NIPj)) is the result of the application of a hash function on a person identifier number (PIN). 3) The method of claim 1, wherein each fingerprint (DH (NIP)) associated with a set of information is the result of the application of a function hash on a code obtained by concatenating a prefix followed by a person identifier number (PIN).

4) The method of claim 1, wherein each fingerprint (DH (DH (NIP))) is the result of a hash function on a first code obtained by concatenation of a first prefix and another fingerprint (DH (NIP)), itself the result of the application of a hash function on a second code obtained by concatenation of a second prefix followed by a person identifier number (PIN). 5) Method according to one of the preceding claims, wherein said first key (lk) is the result of the application of a hash function on a fingerprint of a person identifier number (DH (NIP)).

6) Method according to one of the preceding claims, wherein the first key (lk) is a public key of an asymmetric encryption method.

7) Information equipment (Ei) hosting at least one database in which at least one set of information relating to a person associated with a person identifier number (NIPj) and a fingerprint (DH) is stored (NIPj)) which depends on the person identifier number (NIPj), characterized in that it comprises

means for encrypting each print (DH (NIPj)) with a key (lki), called the first key, which depends on the person identifier number (NIPj) from which said print is issued, in order to obtain a encrypted footprint (C (lki; DH (NIPj)),

means for encrypting the first key (lki) with another key (Pwi), called the second key, in order to obtain an encrypted key (C (PWi, lki)),

means for transmitting to a central equipment unit (Ec) dedicated to linking together sets of information, on the one hand, of the encrypted footprint (C (Iki; DH (NIPj)), and on the other hand, the encrypted key (C (PWi, lki)).

8) Central equipment (Ec) dedicated to linking together sets of information stored in databases hosted in at least one information equipment (Ei) according to claim 8, a second key (PWi) being stored in said central equipment (Ec), characterized in that it comprises

means for decrypting each of the encrypted keys (C (PWi, lki)) transmitted by said at least host communication equipment by means of said second key (PWi) in order to obtain the first key (lki), and

means for decrypting each encrypted fingerprint (C (Iki; DH (NIPj)) transmitted by said at least one piece of information equipment (Ei) by means of the first key (lki) thus decrypted in order to obtain said print (DH (NIPj) of each set of information,

means for linking two sets of information when the fingerprints (DH (NIPj) associated therewith correspond.

9) System for chaining sets of information relating to persons and stored in databases hosted by at least one communication equipment, characterized in that said at least one communication device is in accordance with claim 7 and in that it further comprises an equipment dedicated to the linking of sets of information according to claim 9.