WO2004086313A2

WO2004086313A2 - Method and installation for the image authentication of an object, using a portable storage unit containing stored characteristic image values

Info

Publication number: WO2004086313A2
Application number: PCT/FR2004/000685
Authority: WO
Inventors: Liming Chen; Kun Peng; Yanling Liu
Original assignee: Ecole Centrale De Lyon
Priority date: 2003-03-21
Filing date: 2004-03-19
Publication date: 2004-10-07
Also published as: FR2852715B1; FR2852715A1; WO2004086313A3

Abstract

The invention relates to a method for the image authentication of an object, using a portable data storage unit. The inventive method comprises the following steps consisting in: during a protection phase, taking at least one image of the object; splitting the image into a first part comprising information corresponding to characteristic values of the image and a second part comprising information corresponding to transformation matrices of the image; and storing the first part on the portable unit and the second part on a data storage system. The invention further consists in: during an identification phase, reading the portable unit in order to recover (i) the first information part contained in the portable unit and (ii) the second part comprising information corresponding to said portable unit, which is stored on the storage system; and reconstructing the image from said first and second information parts.

Description

METHOD AND INSTALLATION FOR IMAGE AUTHENTICATION OF AN OBJECT USING A PORTABLE MEMORY UNIT

The present invention relates to the technical field of authentication of an animated or inanimate object such as for example a person or a product in the general sense.

In many applications, the need arises to authenticate or identify an object in a general sense in a secure manner. A known application relates to the control of people wanting to access premises or buildings.

Another known application relates to the identification of an object having for example a significant market value.

To authenticate a person, the prior art has proposed various technical solutions. One of them is to use a portable data storage unit such as a smart card or a magnetic card that identifies its holder. However, it should be noted that such a portable unit can be falsified or stolen so that the identification function of the carrier of the portable unit is no longer ensured.

The present invention therefore aims to remedy the drawbacks of the state of the art by proposing a technique making it possible to authenticate an object in a general sense in a safe and simple manner. To achieve such an objective, the present invention relates to a method of authenticating an object by the image using a portable data storage unit.

According to the invention, it includes the following steps: • in a protection phase: - to take at least one image of an object, to decompose the image into a first part of information corresponding to values characteristic of the image and a second part of information corresponding to image transformation matrices, - storing the first part of information on the portable unit and the second part of information on a data storage system, • and in an identification phase: to read the portable unit in order to recover on the one hand, the first part of information contained in said unit and on the other hand, the second part of information corresponding to said unit portable and stored on the storage system, and to proceed with the reconstruction of the image from the first and second parts of information. According to a preferred embodiment characteristic, the method consists in taking an image of a person integrating biometric data. According to another preferred embodiment of the invention, the method according to the invention consists in storing the first part of information on a portable unit such as a smart card.

According to a first alternative embodiment, the method consists in decomposing the image represented by a matrix A of dimensions M x N (with M> N) by a coding technique of the type of decomposition of singular values for which:

A = UAV ^T with U and V of matrices of dimension M x N and N x N respectively, with orthogonal columns and A, the diagonal matrix of dimension N x N containing the singular values of A on its diagonal. According to this first alternative embodiment consisting in decomposing the image by a coding technique of the type of decomposition of singular values, the method consists:

• to calculate two matrices AA ^T and A ^T A,

• to take for each calculated matrix, n eigenvectors corresponding to the n largest eigenvalues (n "M, n" N),

• to calculate the matrix of singular values according to the formula:

A _op t ⁼ U ₀ pt AV _op t, with U _op t and V _op t the matrices of the n eigenvectors chosen for the matrices AA ^T and A ^T A, and Λ _opt the diagonal matrix of the n first singular values, • to extract the diagonal elements from the diagonal matrix Λ _{op in} order to obtain the n principal singular values,

• to store in the portable unit, the n main singular values, • and to store in the storage system, the matrices U _opt and V _op .

According to this first alternative embodiment, the reconstruction of the image is carried out according to the following formula:

T

A _re ⁼ U ₀ pt Λ ₀ pt V ₀ pt According to a second variant embodiment, the method consists in ensuring image decomposition using an image compression technique of the type of analysis of the main component .

According to this second variant of decomposition of the image by an image compression technique of the type of analysis of the main component, the method consists:

• to calculate the average A of N different images A of an object of dimensions m x n by:

NV mxn ^ jo to calculate two matrices of covariances R <mxm) and C ( _nX n) such that:

NOT _

1

o to choose the q eigenvectors corresponding to the largest eigenvalues for each matrix in order to obtain two matrices of eigenvectors W ^ _pt of dimension mxq and W ^ _pt of dimension nxq, • to calculate the transformed matrix such that:

¹ y (qy.q) = W ^Vt o ^R pt ^{T Α} AW ^YY o ^C pt

• to store in the portable unit, the qxq elements of the transformed matrix Y _(qXq) ,

• and to record in the storage system the matrices W ^ _t and W ^ _t . According to this second variant embodiment, the method consists in reconstructing the image according to the following formula:

- A "-re = W" o ^R ptY (ç <qγ W ^v op ° t ^T Another object of the invention aims to propose an installation for authenticating an object using a portable data storage unit. This installation includes:

Means for transforming an image of an object into a first part of information and into a second part of information,

A portable unit reader adapted to record and read the first part of information on at least one portable unit,

• a data storage system adapted to store the second part of information, • and reverse transformation means which, starting from the first part of information from the portable unit and from the corresponding second part of information from the system storage, allows the image of said object to be reconstructed. Various other characteristics will emerge from the description given below with reference to the appended drawings which show, by way of nonlimiting examples, embodiments of the subject of the invention.

Figure 1 is a schematic view illustrating the principle of the subject of the invention.

Figure 2 is a diagram illustrating a first embodiment of the subject of the invention.

Figure 3 is a schematic view illustrating a second embodiment of the subject of the invention.

Figure 4 is a diagram explaining the second embodiment of the subject of the invention. The object of the invention relates to a method for authenticating an object by an image, using a portable data storage unit. In the description which follows, the object to be authenticated is a person even if it is clear that the present invention also applies to any type of object.

Figure 1 illustrates the implementation of the method according to the invention using an installation 1 structured around a data processing and storage system, known per se such as a computer system in the general sense . The installation 1 comprises means 2 making it possible to transform a so-called original image 3 representing at least a characteristic part of the object to be identified or authenticated. In the example considered, the object is a person and the image taken relates to the face of the person. Of course, provision may be made to take an image 3 which integrates different biometric data relating for example to fingerprints or the iris of the eye.

The means 2 make it possible to transform the image 3 into a first part of information 3a and into a second part of information 3b. Of course, these first and second parts of information are digital in order to be able to be processed by a computer system. The installation 1 also implements at least one portable data storage unit 4 associated with a reader 5, that is to say a system ensuring data transfer between the portable unit 4 and the computer system.

According to a preferred embodiment characteristic, the portable unit 4 is produced by a smart card. However, it should be noted that the portable unit 4 can be produced by a different support such as a magnetic card for example.

According to the invention, the portable unit 4 is adapted to store the first part of information 3a.

The installation 1 also includes a data storage system 6 adapted to store in particular the second part of information 3b. For example, such a data storage system 6 constitutes a database.

The installation 1 also includes means 7 making it possible to ensure a reverse transformation to the transformation carried out by the transformation means 2 with a view to obtaining an image 8 known as reconstructed. These reverse transformation means 7 are adapted to reconstruct the original image from the first part of information 3a from the portable unit 4 and from the second part of information 3b from the storage system 6 and corresponding to said unit. portable 4.

The reconstructed image 8 corresponds to the original image 3 if the reverse transformation operation uses the first part of information 3a and the second part of information 3b coming from the original image 3. In this case, the carrier of the portable unit 4 can be authenticated securely by the reconstruction of an image representing the face of the wearer of the portable unit 4. In the case where the reconstruction of an image is not carried out from the first part of information 3a and / or from the second part of information 3b corresponding to said image, the reconstructed image such as 8 is disturbed. In the illustrated case, the image 3ι, said to be original, of which part of the information obtained by the transformation means 2ι, identical or similar to the transformation means 2 is integrated in a portable unit 4ι cannot be reconstructed by the means of reverse transformation 7 if the second part of information 3b used does not come from the same original image. The reconstructed image 8ι is disturbed and does not allow the person or the object of the original image to be recognized. In other words, the object of the invention is a means of protection against fraudsters because changes made to only one of the parts of information recorded on the portable unit 4 or on the storage system 6 does not allow to reconstruct the original image.

The method of authenticating an object and in the present case of a person follows directly from the above description.

It must be considered that the authentication method according to the invention comprises a first phase called protection followed by a second phase called identification or authentication.

During the protection phase, at least one original image 3 is taken, representing at least part of the object to be identified. Such a digitized image 3 is broken down into a first part of information 3a and a second part of information 3b. The first part of information 3a is stored on a portable unit 4 while the second part of information 3b is recorded on the storage system 6. Of course, each second part of information 3b is identified so that it can be attached to the first part of corresponding information 3a, that is to say the corresponding portable unit 4.

When the identification of an object and in this case a person is to be carried out, the portable unit 4 is read in order to recover the first part of information 3a contained in said unit. Likewise, the second part of information 3b recorded on the data system 6 and corresponding to said portable unit 4 is recovered. Preferably, the reading of the portable unit 4 automatically provides the information necessary to recover the second part information 3b corresponding to said portable unit 4. From the first 3a and second 3b parts of information recovered, an image is reconstructed. If the two pieces of information 3a, 3b corresponding to an image are not associated, the original image cannot be found, as explained above. According to a preferred characteristic of embodiment, the first part of information 3a stored on the portable unit 4 is defined by essential characteristics of the image so that the absence of such information leads to a significant alteration of the reconstructed image. . Given the storage capacity of the portable unit 4, the method according to the invention provides for compression or coding of the first part of information 3a intended to be stored in the portable unit 4. Thus, advantageously, the first part of information 3a corresponds to characteristic values of the image 3 while the second part of information 3b corresponds to image transformation matrices.

The description which follows describes a first alternative embodiment consisting in decomposing the original image 3 represented by a matrix A of dimensions M x N with M> N, by a coding technique of the type of decomposition of singular values for which:

A = UΛV ^T with U and V of matrices of dimension M x N and N x N respectively, with orthogonal columns and A, the diagonal matrix of dimension N x N containing the singular values of A on its diagonal.

As shown more precisely in FIG. 2, according to this coding technique of the type of decomposition of singular values, the method consists:

• to calculate two matrices AA and A A, • to take for each calculated matrix, n eigenvectors corresponding to the n largest eigenvalues (n "M, n" N),

• to calculate the matrix of singular values according to the formula:

A ^J opt = U ^w o ^T pt A- ™ -V * opt with U _opt and V _op t the matrices of the n eigenvectors chosen for the matrices AA ^T and A ^T A, and Λ _op t the diagonal matrix of the n prime singular values,

• to extract the diagonal elements from the diagonal matrix Λ _{opt in} order to obtain the n principal singular values, • to store in the portable unit, the n main singular values,

• and to memorize in the storage system, the matrices U _opt and V _opt . When a portable unit 4 is introduced into its reader 5 in order to obtain the authentication of its holder, the system recovers the two matrices of eigenvectors U _opt and V _opt corresponding to the portable unit 4 identified. From these two vector matrices and the diagonal matrix of the singular values, formed from the values extracted from the portable unit 4, an Are image is reconstructed according to the following formula:

A _re ⁼ U _op t Λ _op t V _o t If the matrices provided by the data storage system and the singular values from the portable unit come from the same image, then the latter will be correctly reconstructed. However, if a modification has occurred in the information contained on the portable unit 4 or in the packaging system 6, a disturbed image 8ι will be reconstructed. Figures 3 and 4 illustrate a second alternative embodiment for compressing the image stored in the portable unit 4. This second alternative consists in ensuring a decomposition of an image using a technique of analysis type of the main component. According to the invention, this method of analysis of the main component is suitable for compact and secure coding of images to capture the main characteristics of a series of images A of the same object in order to be able to reconstruct each of these images by a single transformation. The method consists for this image coding technique:

• to calculate two matrices of covariances R ( _mm) e C ( _nxn) such that:

To choose the q eigenvectors corresponding to the largest eigenvalues for each matrix in order to obtain two matrices of eigenvectors W _t of dimension mxq and W _gt of dimension nxq,

• to calculate the transformed matrix such that: y (qxq) = W o ^R pt ^T A ^Λ W ^rr o ^C pt

• to store in the portable unit, the qxq elements of the transformed matrix Y _qXq) ,

• and to record in the storage system the matrices W _t and W% _t . When a portable unit 4 is introduced into the reader 5 for an authentication procedure, the two eigenvector matrices W _t and W ^ _t are supplied by the corresponding storage system of the portable unit 4 read . From these matrices and the matrix of the compressed image extracted from the portable unit 4, the image A _re is reconstructed by the following formula

^Α Are - w ⁿ o ^R pt ¹ γ (qxq) w ^π op ^c t ^τ If the two matrices provided by the storage system and the characteristic values from portable unit 4 come from images of the same object, each image will be correctly reconstructed. If on the other hand the portable unit 4 contains modified information, a disturbed image will be reconstructed.

The invention is not limited to the examples described and shown since various modifications can be made without departing from its scope.

Claims

1 - Method for authenticating an object by the image using a portable data storage unit, characterized in that it comprises the following steps:

• in a protection phase: to take at least one image of an object, to decompose the image into a first part of information corresponding to characteristic values of the image and into a second part of information corresponding to image transformation matrices, to store the first part of information on the portable unit and the second part of information on a data storage system, o and in an identification phase: to read the unit portable in order to retrieve on the one hand, the first part of information contained in said unit and on the other hand, the second part of information corresponding to said portable unit and stored on the storage system, - and to proceed to the reconstruction of the image from the first and second parts of information.

2 - Authentication method according to claim 1, characterized in that it consists in taking an image of a person integrating biometric data.

3 - authentication method according to claim 1, characterized in that it consists in storing the first part of information on a portable unit such as a smart card.

4 - Authentication method according to claim 1 or 3, characterized in that it consists in decomposing the image represented by a matrix A of dimensions M x N (with M> N) by a decoding type coding technique of singular values for which:

A = UΛV ^T with U and V matrices of dimension M x N and N x N respectively, with orthogonal columns and Λ, the diagonal matrix of dimension N x N containing the singular values of A on its diagonal.

5 - Authentication method according to claim 4, characterized in that it consists, for decomposing the image by a coding technique of type of decomposition of singular values:

• to calculate two matrices AA ^T and A ^T A,

• to take for each calculated matrix, n eigenvectors corresponding to the n largest eigenvalues (n "M, n" N), • to calculate the matrix of singular values according to the formula:

with U _opt and V _opt the matrices of the n eigenvectors chosen for the matrices AA ^T and A ^T A, and Λ _op t the diagonal matrix of the n first singular values,

• to extract the diagonal elements from the diagonal matrix Λ _{opt in} order to obtain the n principal singular values, o to store in the portable unit, the n principal singular values, β and to store in the storage system, the matrices U _opt and V _opt .

6 - authentication method according to claim 4, characterized in that it consists in carrying out the reconstruction of the image according to the following formula: A _re - U _op t Λ _op t V _op t

7 - Authentication method according to claim 1, characterized in that it consists in ensuring an image decomposition using a type of analysis technique of the main component.

8 - Authentication method according to claim 7, characterized in that it consists, in order to decompose the image by a technique of type of analysis of the main component:

• to calculate the average of N different images A of an object of dimensions m x n by:

1 N d m, n

N i mXn _{ j _{= 1} "to calculate two matrices of covariances R ( _mxm ) and C _(nxn ) such that: NOT

T

(xm) j (mxn) (mxn) A - "(mxn) -" (nixn)

1

To choose the q eigenvectors corresponding to the largest eigenvalues for each matrix in order to obtain two matrices of eigenvectors W ^R _pt of dimension mxq and W _gpt of dimension nxq,

• to calculate the transformed matrix such that:

¹ Y (qxq) = W ^VY o ^R pt ^{T Λ} AW ^YY o ^C pt

T • and to register in the storage system, the matrices W _pt and W r ^ C _t .

9 - authentication method according to claim 8, characterized in that it consists in reconstructing the image according to the following formula:

^Λ Are - ^"""w" o ^R pt ¹ Y (qx _q γ W ^t o ^c pt ^τ

10 - Installation for authenticating an object using a portable data storage unit, characterized in that it comprises:

° means for transforming an image of an object into a first part of information and into a second part of information, ^s a portable unit reader adapted to record and read on at least one portable unit, the first information part, ^“ a data storage system adapted to store the second part of information, • and reverse transformation means which, starting from the first part of information from the portable unit and from the second part of corresponding information from the storage system, allows the image of said object to be reconstructed.