WO2005112009A2

WO2005112009A2 - Method and apparatus for optical authentication

Info

Publication number: WO2005112009A2
Application number: PCT/IL2005/000508
Authority: WO
Inventors: Samuel Kosolapov
Original assignee: Samuel Kosolapov
Priority date: 2004-05-19
Filing date: 2005-05-16
Publication date: 2005-11-24
Also published as: WO2005112009A3; IL162063A0

Abstract

An optical authentication device (Fig. 8, 1) comprising a plurality of elements having optical polarizing properties distributed in a pseudo-random manner over a predetermined area (33); at least three optically detectable markers (29, 30, 31, 32) positioned in predetermined positions with respect to the predetermined area; whereby, when viewing the predetermined area with an optical imaging sensor of a reader under an illumination having specific polarization properties a first image is obtained that is different from one or more other images obtained under one or more illuminations having different polarization properties, thus by comparing two or more images of at least a portion of the device to saved images of the same device or a portion thereof taken under the same illuminations, using the markers (29, 30, 31, 32) for aligning images to be compared, authentication is achieved.

Description

METHOD AND APPARATUS FOR OPTICAL AUTHENTICATION

Field of the Invention

The present invention relates to the field of authentication. More particularly, the present invention relates to methods and apparatus for simple and inexpensive authentication and authorization by utilizing unique optical keys that can not be duplicated, forged or copied in an inexpensive way and, therefore, may be used as reliable authentication tools. Additionally, this invention relates to methods and apparatus for reliable, simple and inexpensive evaluation of properties of above- mentioned keys in order to ensure reliable authentication of such keys by authentication apparatus (reader apparatus).

Background of the Invention

Modern society increasingly employs various techniques for authentication and authorization. Such techniques are presently used in many areas of our daily life, ranging from transaction authorization to identity checks. For example, magnetic cards and magnetic cards readers are popular tools that are often used for authentication and authorization, hi such cases, a magnetic card needs to be inserted into a magnetic card reader in order to either authenticate a registered user, or commence a transaction. Then, the information, which is recorded on the designated magnetic stripe, is automatically evaluated by an authorization server that, in turn, either authorizes or rejects the transaction. Unfortunately, magnetic cards are prone to unauthorized copying resulting in a great number of forgeries. Many such cases are notoriously known.

The problem is that any person skilled in the art may easily duplicate original magnetic cards by simply copying the digital data written on any original magnetic card onto the forged card. In such cases, a magnetic card reader will not be able to distinguish between the original card and its duplicate. Short passwords that are sometimes used provide only limited protection since such password can be intercepted by utilizing various hacker techniques, well known in the public domain. Another well known example of a modern authentication solution consists of Smart Cards and a Smart Card readers. Still, despite many emerging technologies aimed at protecting Smart Cards from unauthorized copying, anyone skilled in the art is capable of creating an illegal duplicate of such Smart Card. Once such unauthorized duplicate is created, the Smart Card reader technology will not be able to distinguish between the original card and its forgery.

Other known examples of authentication solutions also include optical ID (one- dimensional) and 2D (two-dimensional) bar-codes, optical "Safe Cards" and many others. However, such solutions are not capable of distinguishing between original cards and their duplicates.

Many authentication solutions may optionally contain protection elements that can not be easily copied, i.e. photographs with unique layover stamps, complex holograms, drawings with small irregularities, pressure sensitive devices, color and ultraviolet marks, etc. However, such protection elements are designed in order to be authenticated manually by a human operator. Notwithstanding, such protection elements cannot be easily validated in an automated fashion.

Additionally, well known examples of authentication systems also include biometry. It is assumed that each user has unique set of biometrical data, such as, for example, fingerprints, face shape, voice, etc. By measuring relevant parameters, authentication is achieved. Unfortunately, current biometry-based implementations are unreliable. For example, most optical fingerprint systems may be circumvented by gelatin-made finger imprints. Another well known problem of biometry systems lies in the fact that sensitive biometry data, once stolen, may be easily misused for illegal activities.

US4490790 proposes a method for discriminating authenticity of a bill by evaluating polarization characteristics of specially embedded into said polarized component by utilizing one light source and two light-receiving elements. Effectively this setup measures polarization characteristics in only one point of the bill, which may not be good enough for the strict requirements of today's authentication systems. US4476468 proposes protection of magnetic card by addition of a strip containing light changing crystals (Polaroid) modulating light beam. The proposed design requires mechanical movement of the card in the direction of the strip. However, standard magnetic readers have allowed vertical shift tolerance of about 1 mm that limits the size of said polarizer to practical value of say 1mm x 1mm, thus the proposed strip can not be considered non-forgeable enough, whereas lower sizes will provide unacceptable high false negative rate.

Patent application WOO 160047 described "automated authentication of documents protected with security features" according to which one or more imaging sensors detects spectral and geometric distribution, degree of polarization and/or alignment by illuminating protected document by using different illumination means. Unfortunately, the drawings and description do not take into account that different instances of digital cameras have different optical and spectral characteristics, different instances of light sources have different spectral and light distribution characteristics, and that all above together combined with the known fact that any mechanical misalignment in the proposed setup will lead to creation of significantly different images of the same protected document for different setups. Said patent application does not provide any practical way of defining said spectral and polarization characteristics specifically for the goals of the proposed applications.

US5974150 proposes "System and method for authentication of goods" according to which at least two CCD sensors detect the attribute (angle of rotation of polarization) and position of irregular bundle of dichroic fibers containing fluorescent dye by illuminating said bundle by a light. Despite that the proposed implementation utilizes relatively powerful lamp/laser, the light generated by fluorescent dye is weak, thus limiting practical size of pixel to relatively large size of 0.3mm X 0.3mm. The proposed method of calculating attribute requires exact alignment of the two CCDs (each having its polarization filter) relative to an object in test and it is asserted that the proposed method may provide unacceptably high false negative rate because of inevitable variations in real life of light source's and CCD's parameters and their relative positioning. Detailed description of this patent does not provide means for compensating for those inaccuracies. An additional possible reason for anticipated high false negative rate is high camera noise (because of low-light work mode). Proposed compensation of this noise by utilizing frames averaging may require unacceptably high acquisition time.

US2005/0047593 proposes method of guaranteeing the authenticity of documents by utilizing embedded into document optically prominent particles having specific optical properties (such as fluorescent, phosphorescent, polarization sensitive, viewing angle dependent, etc.). However this patent application does not provide description of apparatus for reliable evaluation of such properties in the real-life conditions.

hi other words, all of the above-mentioned solutions do not provide reliable, cost efficient and fully automated authentication and authorization.

It is therefore an object of the present invention to provide a way of producing inexpensive Unique Optical Key which can be easily implemented for mass production.

It is another object of the present invention to provide a way of evaluating relevant properties of above-mentioned Unique Optical Key.

It is still another object of the present invention to provide a compact Optical Key

Reader apparatus that is capable of reliably evaluate relevant properties of the Unique Optical Key which apparatus is inexpensive, easy to operate and reliable..

It is still another object of the present invention to provide a compact Optical Key Reader apparatus wherein the accuracy of arrangement of its optical components, relative to one another, and quality of such optical components are not critical to the apparatus's proper functioning.

It is a further object of the present invention to provide an Optical Key Reader apparatus that is capable of operating rapidly or essentially in "real-time".

It is a further object of the present invention to provide a method of reliable authentication by using evaluated properties of the Unique Optical Key. Other objects and advantages of the invention will become apparent as the description proceeds.

Summary of the Invention

There is thus provided, in accordance with some preferred embodiments of the present invention, an optical authentication device comprising: a plurality of elements having optical polarizing properties distributed in a pseudorandom manner over a predetermined area; at least tliree optically detectable markers positioned in predetermined positions with respect to the predetermined area; whereby, when viewing the predetermined area with an optical imaging sensor of a reader under an illumination having specific polarization properties a first image is obtained that is different from one or more other images obtained under one or more illuminations having different polarization properties, thus by comparing two or more images of at least a portion of the device to saved images of the same device or a portion thereof taken under the same illuminations, using the markers for aligning images to be compared, authentication is achieved.

Furthermore, in accordance with some preferred embodiments of the present invention, the device is further provided with at least one public identification detail that is optically distinguishable in a machine readable form.

Furthermore, in accordance with some preferred embodiments of the present invention, the device is further provided with at least one additional area containing a plurality of elements having optical polarizing properties distributed in a pseudorandom manner, for validating interaction with a specific reader.

Furthermore, in accordance with some preferred embodiments of the present invention, at least a portion of each element is fully or partially optically transparent, so as to allow incident illumination to pass through the device. Furthermore, in accordance with some preferred embodiments of the present invention, at least a portion of each element is fully or partially optically reflective, so as to allow incident illumination to be reflected from the device.

Furthermore, in accordance with some preferred embodiments of the present invention, at least some of the elements of optical polarizing properties comprise elements changing orientation of polarization of incident illumination of specific polarization orientation.

Furthermore, in accordance with some preferred embodiments of the present invention, at least some of the elements of optical polarizing properties comprise elements exhibiting properties of linear polarization filters.

Furthermore, in accordance with some preferred embodiments of the present invention, at least one of the elements of optical polarizing properties comprise an element having predetermined shape and position exhibiting properties of linear polarization filters.

Furthermore, in accordance with some preferred embodiments of the present invention, one or more of the elements has its own spectral properties.

Furthermore, in accordance with some preferred embodiments of the present invention, the device is further provided with one or more fluorescent elements.

Furthermore, in accordance with some preferred embodiments of the present invention, there is provided a reader apparatus for reading the device, the apparatus comprising: a source of a light beam a first polarizer for modifying in a controllable manner the polarization of the light beam; a holder for holding the device in the optical path of the beam; a second polarizer for modifying in a controllable manner the polarization of the light beam after it passes through or reflected from the device; a controller for controlling the first polarizer or the second polarizer or both; an optical imaging sensor for obtaining different images of the device in different polarization orientations of the first polarizer or the second polarizer or both; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison.

Furthermore, in accordance with some preferred embodiments of the present invention, the holder further comprises an additional area comprising a plurality of elements having optical polarizing properties distributed in a pseudo-random manner, wherein at least a portion of each element is fully or partially optically transparent, for validating interaction with a specific optical authentication device.

Furthermore, in accordance with some preferred embodiments of the present invention, there is provided a reader apparatus for reading the device of claim 1, the apparatus comprising: a plurality of controllable sources of light beams each source having its own polarizer for polarizing its light beam in a predetermined polarization orientation; a holder for holding the device in the optical paths of the beams; a controller for controlling separately or in combinations said plurality of controllable sources of light beams; an optical imaging sensor for obtaining different reflected images of the device illuminated by a chosen combination of one or more light beams of said plurality of controllable sources of light beams; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison.

Furthermore, in accordance with some preferred embodiments of the present invention, the apparatus is further provided with a controllable polarizer filter positioned between the holder and the optical imaging sensor.

Furthermore, in accordance with some preferred embodiments of the present invention, the apparatus is further provided with one or more ultraviolet illumination sources for illuminating the device and detecting fluorescent elements. Furthermore, in accordance with some preferred embodiments of the present invention, the apparatus is further provided with one or more illumination sources each having its own filter having predetermined spectral properties.

Furthermore, in accordance with some preferred embodiments of the present invention, one or more of the polarizers has its own predetermined spectral properties.

Furthermore, in accordance with some preferred embodiments of the present invention, there is provided a method for authentication comprising: providing a reader apparatus comprising: a source of a light beam; a first polarizer for modifying in a controllable manner the polarization of the light beam; a holder for holding a device to be authenticated and in the optical path of the beam; a second polarizer for modifying in a controllable manner the polarization of the light beam after it passes through or reflected from the device; a controller for controlling the first polarizer or the second polarizer or both; an optical imaging sensor; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison; placing the device on the holder and obtaining different images of the device in different polarization orientations of the first polarizer or the second polarizer or both; comparing the obtained images with image information stored in a database of optical authentication devices, each device comprising: a plurality of elements having optical polarizing properties distributed in a pseudo-random manner over a predetermined area; at least three optically detectable markers positioned in predetermined positions with respect to the predetermined area authenticating the device if the obtained images match or are close enough to stored images of a device, or rejecting the device if differences larger than a predetermined level are found.

Furthermore, in accordance with some preferred embodiments of the present invention, the method further comprises providing a public identification detail to each device to be authenticated and using the same public identification detail when comparing the obtained images with image information in the database.

Furthermore, in accordance with some preferred embodiments of the present invention, there is provided a method for authentication comprising: providing a reader apparatus comprising: a plurality of controllable sources of light beams each source having its own polarizer for polarizing its light beam in a predetermined polarization orientation; a holder for holding the device in the optical paths of the beams; a controller for controlling separately or in combinations said plurality of controllable sources of light beams; an optical imaging sensor; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison; placing the device on the holder and obtaining different reflected images of the device illuminated by a chosen combination of one or more light beams of said plurality of controllable sources of light beams different polarization orientations of the first polarizer or the second polarizer or both; comparing the obtained images with image information stored in a database of optical authentication devices, each device comprising: a plurality of elements having optical polarizing properties distributed in a pseudo-random manner over a predetermined area; at least three optically detectable markers positioned in predetermined positions with respect to the predetermined area authenticating the device if the obtained images match or are close enough to stored images of a device, or rejecting the device if differences larger than a predetermined level are found.

Brief Description of the Drawings

Fig. 1 schematically illustrates a general layout and functionality of authentication system.

Fig. 2 schematically illustrates one simplest explanatory implementation of the Unique Optical Key physically embedded into optically transparent Card.

Fig. 3 schematically illustrates the main components of an Optical Key Reader according to the simplest exemplary embodiment of the present invention.

Fig. 4 schematically illustrates the operation of Optical Key Reader according to the simplest exemplary embodiment of the present invention.

Fig. 5 schematically illustrates the effect of Second Linear Polarizing Filter Rotation.

Fig. 6 schematically illustrates one possible practical implementation of the Unique Optical Key physically embedded into Card.

Fig. 7 schematically illustrates additional unique optical member integrated into Optical Key Reader in order to enable reliable authentication of said Optical Card Reader and in order to provide additional security features (described further). Fig. 8 schematically illustrates one possible implementation of the Unique Optical

Key having special markers and other elements designed to ensure reliable operation of the Optical Key Reader.

Fig. 9 schematically illustrates the operation of Optical Key Reader according to the exemplary embodiment of the present invention.

Fig 10 schematically illustrates the operation of another implementation of the Optical Key Reader modified for reflection-based Card.

Fig 11 schematically illustrates the operation of yet another implementation of the Optical Key Reader (modified for reflection-base Card) having fixed number of stationary positioned linear Polarization filters.

Fig. 12 schematically illustrates main electronic blocks of an authentication system in accordance with a preferred embodiment of the present invention.

Detailed Description of Preferred Embodiments

The present invention introduces simple novel method and apparatus for authentication.

The present invention is characterized in that the method for authentication utilizes Unique Optical Key. This Unique Optical Key holds unique pseudorandom pattern which can not be easily reproduced.

The present invention also provides an Optical Key Reader apparatus, which can reliably recognize unique pseudorandom pattern and encode said pattern, in full or in part, into a digital form.

The present invention also provides a Processing and Comparison Unit, which is connected via a communication link to an Optical Key Reader. Processing and Comparison Unit can control operation of Optical Key Reader by sending commands, which are recognized by the reader as REQUEST, accept digitally encoded data describing unique pseudorandom pattern as RESPONSE, and authenticate Unique

Optical Key by evaluating data contained in the RESPONSE to the specific REQUEST.

According to one aspect of the present invention, Unique Optical Element has physical properties, such that when viewed with known certain optical setup a known pseudorandom pattern is get by Optical Key Reader, and when viewed with second known certain optical setup a second known pseudorandom pattern is get by Optical Key Reader, which physical properties are very difficult to reproduce.

According to another aspect of the present invention, a number of possible optical setups, whereas each specific setup generates predetermined pseudorandom pattern that is significantly different from other pseudorandom patterns, is large or very large, thus making duplication of Unique Optical Key extremely difficult or practically impossible. .

According to another aspect of the present invention, specific known optical setup of the Optical Key Reader may be selected remotely by sending to the reader specially encoded command containing arguments requesting such specific optical setup.

The present invention is additionally characterized in that only chosen segments of the above pseudorandom patterns can be used for the authentication.

According to one aspect of the present invention, this limited set of selected segments of selected pseudorandom patterns is chosen pseudo randomly.

According to one aspect of the present invention, Optical Key Reader apparatus can reliably read specific segment of any specific pseudorandom pattern and encode said segments in digital form.

According to one aspect of the present invention, specific known segments of specific pseudorandom patterns may be selected remotely by sending to the Optical Key Reader specially encoded commands with proper arguments, i.e. REQUEST. The present invention is additionally characterized in that whenever Unique Optical

Key is properly positioned relative to Optical Key Reader, and whenever properly selected REQUEST is sent to the Optical Key Reader by the Processing and Comparison Unit, the above Optical Key Reader returns specific RESPONSE to the Processing and Comparison Unit. Taking into account the fact that pseudorandom patterns are used, it is assumed, that, in most cases, specific REQUEST generates a different RESPONSE for each specific Unique Optical Key.

The present invention is additionally characterized in that each Unique Optical Key must be initialized before usage. During initialization process specific Unique Optical Key is properly positioned inside Optical Key Reader. Then, Processing and Comparison Unit generates (by using any appropriate pseudorandom algorithm) a set of REQUESTS and by sending said set of REQUESTS to Optical Key Reader, records a set of relevant RESPONSES. It is therefore assumed that for each Unique Optical Key different unique sets of {REQUEST-RESPONSE} pairs will be generated.

According to another aspect of the present invention, practical implementation of the Unique Optical Key enables generating a large number of such unique pairs, large enough in order to exclude direct guessing attack while minimizing server storage requirements.

According to one aspect of the present invention, each pair {REQUEST-RESPONSE} will be used for authentication of each specific Key only once, thus eliminating the possibility, that such pair may be misused, both when generated either legally (for example in the process of a valid transaction), or illegally (for example by illegally monitoring communication line between Optical Key Reader and Processing and Comparison Unit). In such case, a specific Unique Optical Key may be used only for a limited number of times after which it can be discarded or returned for re- initialization.

According to yet another aspect of the present invention, each Unique Optical Key may be initialized several times by different Processing and Comparison Units while each of these units stores its own unique set of pairs {REQUEST-RESPONSE} for each specific Key. This behavior may be useful in order to reduce the number of Keys in the possession of a specific person. Optionally, the same Unique Optical Key may be used for several applications simultaneously, while each application uses its own statistically different set of pairs {REQUEST-RESPONSE} for the authentication optionally by utilizing different Processing and Comparison Units for communication.

According to yet another aspect of the present invention, security level maybe regulated dynamically by properly setting the maximum allowed number of pairs {REQUEST-RESPONSE} used for authentication. Here, the more pairs are used for the authentication, the fewer are the chances that a brute-force random "guessing" attack would result in positive authentication.

According to the one embodiment of the current invention, Unique Optical Key is formed (in full or in part) from optically transparent substrate on the surface of which (or inside the body of which) Plurality of Small Birefringent Elements and or Linear Polarizing Elements are pseudo randomly dispersed, each element having unique shape, position, orientation and color.

According to another embodiment of the current invention, Unique Optical Key is formed (in full or in part) from optically reflecting substrate on the surface of which Plurality of Small Birefringent Elements and Linear Polarizing Elements are pseudo randomly dispersed, each element having unique shape, position, orientation and color.

According to yet another embodiment of the current invention, Unique Optical Key is positioned on the surface of the standard plastic card which card can optionally contains additional authentication means, such as magnetic passes, SmartCards, images, holograms, biometry data, etc.

According to the one embodiment of the current invention, Optical Key Reader consists of non-polarized white light source, first linear polarizing element, direction of polarization of which may be changed in a controlled fashion, Key Holder for proper positioning of the Unique Optical Key relative to other elements of the reader, second linear polarizing element, direction of polarization of which may be changed in a controlled fashion and imaging element providing pattern resembling optical properties of the Unique Optical Key, which pattern, later, can be converted into digital form (for example into digital image).

According to the one embodiment of the current invention, said light source, imaging element, first and second linear polarizing elements and optically transparent Unique Optical Key are positioned along common optical axis, h this embodiment rotation of first and/or second linear polarizing element will provide different patterns (images) according to the goals of the current invention.

According to the one embodiment of the current invention, a light source, as well as a first linear polarizing element are positioned around the first optical axis, whereas a second polarizing element and an imaging element are positioned around the second optical axis, and, whereas, first and second optical axes intersect at some point and, whereas, reflection-based Unique Optical Key is positioned at the point of intersection, h tins embodiment, rotation of first and/or second linear polarizing element(s) will provide different patterns (images) according to the goals of the current invention.

According to yet another embodiment of the current invention, Unique Optical Key and Key Holder have additional special optically active and optically inactive elements, regions and markers in order to ensure reliable calibration of the Optical Key Reader, thus preventing affects of possible inaccuracies resulting from relative positioning of the elements of the Optical Key Reader.

According to the one embodiment of the current invention, first and/or second linear polarizing elements are linear polarizing filters that are rotated around optical axis by any appropriate mechanical means, controlled electronically according to the REQUEST.

According to another embodiment of the current invention, first and/or second linear polarizing elements are any appropriate optically active elements, polarization properties of which may be changed by applying electrical or magnetic fields, strength of which may be controlled electronically according to the REQUEST. According to another embodiment of the current invention, an imaging element can be either a standard monochrome, or color video (or still digital camera), converting a specific optical pattern into a digital image, whereas each pixel of this image can be accessed upon REQUEST, and thus returning either monochrome, or {R, G, B} value of this pixel as RESPONSE.

According to yet another embodiment of the current invention, some combination of the values of the pixels of the region specified in the REQUEST will be calculated and returned as RESPONSE, thus preventing inaccuracies of the imaging elements from influencing the authentication results.

According to yet another embodiment of the current invention, Optical Key Reader contains a plurality of light sources, each having its own linear polarizing element aligned at a specific angle relative to reflective Unique Optical Key and one Imaging Element (optionally having Linear Polarizing Filter with controlled or fixed orientation) monitoring the surface of the Unique Optical Key. In such embodiment, different patterns are generated by electronically switching on/off specific light sources.

According to yet another embodiment of the current invention, light source may have any appropriate electronically, controlled in accordance with REQUEST means that enable changing of spectral compound of the light source, and, therefore, providing additional patterns encoded by unique color patterns of the Unique Optical Key (defined either by unique optical transmission spectra, or by optical reflection spectra of the specific segment of the Key) in combination with polarization properties of such Unique Optical Key and thus making duplication of such Unique Optical Element more difficult.

According to yet another embodiment of the current invention, additional Ultraviolet light sources controlled electronically in accordance with REQUEST may be used in order to excite some regions of the Unique Optical Element, therefore, leading to fluorescence of said regions, thus providing even more patterns making duplication of Unique Optical Element even more difficult. Reference is now made to the accompanying drawings.

Fig. 1 schematically illustrates a general layout and functionality of one possible implementation of the Authentication System. Card 1 containing Unique Optical Key is physically inserted into Optical Key Reader 2 (reader apparatus), connected by Communication Links 3 and 4, to Processing Unit 5, which is connected by Communication Link 6 to Service Provider Unit 7. After Card 1 is inserted, Optical Key Reader 2 communicates with Processing Unit 5 by using Communication Links 3 and 4 according to Authentication Protocol described further and, in case of Positive Authentication, Processing Unit 5 sends signal enabling the service (for example, "open the gate") to Service Provider Unit 7 by using Communication Link 6.

Fig. 2 schematically illustrates one simplest and explanatory implementation of the Unique Optical Key using optically-transparent (or semi-transparent) Birefringent

Element 8 physically embedded into Optically Transparent Region 9 of Card 1. h this explanatory implementation, Birefringent Element 8 has Arrow shape resembling direction of optical alignment of the underlying molecules of the Element 8 and is positioned in the center of the Card 1, "arrow" pointing upwards. Practically, Birefringent Element 8 may have any arbitrary shape and may be positioned at any arbitrary place of the dedicated for that goal zone of the Card 1.

Fig. 3 schematically illustrates the main components of Optical Key Reader 2 according to the simplest exemplary embodiment of the present invention. White Light Source 10 (optionally inexpensive Standard Spot Lamp or White LED) provides non-polarized white light in the direction of the Main Optical Axis 11. First Linear Optical Polarizer 12 (optionally inexpensive thin film linear polarizer), Optical Axis of which 13 currently points upward, converts non-polarized light of White Light Source 10 to linearly polarized light direction of polarization of which 15 coincides with direction of Optical Axis 13. Direction of Polarization 15 can be optionally changed by rotating First Linear Polarizing Filter 12 around Main Optical Axis 11 by using controllable rotation means 14 (optionally, said controllable rotation means can be a stepper motor that is controlled by electronic controller of Optical Key Reader 2 according to Authentication Protocol described further). Linearly Polarized Light passes between Horizontal Guiding Members 16 and 18 and Vertical Stopper 17, and thus Direction of Polarization 19 of Linearly Polarized Light is not changed compared to Direction of Polarization 15. This Linearly Polarized Light passes through Second Linear Polarizing Filter 20 (Optical Axis of which 22 currently points upward) which filter passes linearly polarized light practically without modification and thus direction of polarization 23 coincides with direction of arrow 22. The direction of Polarization 23, after passing through the Second Linear Polarizing Filter 20 may optionally be changed by rotating Linear Polarizing Filter 20 around Main Optical Axis 11 by using rotation means 21 (optionally stepper motor controlled by electronics controller of Optical Key Reader 2 according to Authentication Protocol described further). Linearly Polarized Light with direction of polarization 23 passes through Lens 24 (preferably made from material that would not significantly change Direction of Polarization 23, for example glass) and focuses on Imaging Element 25 (optionally standard CCD or CMOS) operation of which is controlled by electronic controller of the Optical Key Reader 2.

Fig. 4 schematically illustrates the operation of Optical Key Reader 2 according to the simplest exemplary embodiment of the present invention, h this example, Card 1 containing Unique Optical Key with optically-transparent Birefringent Element 8 and with Optically Transparent Region 9 is physically inserted into Optical Key Reader 2 and properly positioned inside it by using horizontal and vertical guiding members 16, 17 and 18. Optical 2D image of Card 1 focuses on the Imaging Element 25. When Linearly Polarized Light with Polarization Direction 15 passes through Optically Transparent Region 9 of Card 1, no change of direction of polarization takes place and correspondent regions of the Imaging Member 25 are seen as "white". When Linearly Polarized Light with Polarization Direction 15 passes through Birefringent Element 8 of Card 1, Direction of Polarization 19 changes according to optical properties of the Birefringent Element 8 and thus does not coincide with direction of Optical Axis 22 of Second Linear Polarizing Filter 20. Direction of Polarization 23, after passing through the Second Linear Polarizing Filter 20, is not changed, but intensity of light that passes through Birefringent Element 8 will lessen, and thus correspondent regions on the Imaging Member 25 will appear as "gray" region of some Gray Level. This Gray Level is a function of optical properties of Birefringent Element 8. It means that pixels of the resulting image of Imaging Element 25 are "white" in regions corresponding to Optically Transparent Region 9 and "gray" in regions corresponding to Birefringent Element 8.

Fig. 5 schematically illustrates the effect of rotation of Second Polarizing Filter 20. When Second Linear Polarizing Filter 20 rotates about main Optical Axis 11 there is a certain position where its Optical Axis 22 coincides with Direction of Polarization 19. In such case, Direction of Polarization 19 (before passing Second Linear Polarizing Filter 20) coincides with Direction of Polarization 23 (after passing Second Linear Polarizing Filter 20). hi this case, pixels of resulting image of the Imaging Element 25 will be "white" in regions corresponding to Birefringent Element 8 and "gray" in regions corresponding to Optically Transparent Region 9 (since Optical Axes of First and Second Linear Polarizing Filters 13 and 22 do not coincide). This means that pixels of the image obtained from embodiment of Fig. 4 are different from correspondent pixels of the image obtained from embodiment of Fig. 5.

Generally speaking, Gray Level of pixel of image focused on Imaging Element 25 (optionally CCD or CMOS) can be described by formula [1] as:

where:

/- Gray Level of the pixel (optionally having values from 0 (Level of Black) to 255 (Level of White) ).

Row - Row of the current pixel (optionally having values from 0 to 479 or more for MegaPixel imaging elements)

Column - Column of the current Pixel (optionally having values from 0 to 639 or more for Megapixel imaging elements)

Fi - Some mathematical function. Theoretically this function may be derived with some level of accuracy by using well-known laws of physics, but practically exact nature of this function is of no importance for the goals of present invention. θi - Angle between vertical Axis and Optical Axis 13 of the First Linear Polarizing Filter 12.

02- Angle between vertical Axis and Optical Axis 22 of the Second Linear Polarizing Filter 20.

θ(x,y) - Angle of rotation of the plane of polarization by the Optically Active (Biefringent) Element 8 with coordinates {X,Y} .

X - Horizontal Coordinate measured in some coordinate system associated with Card 1.

Y- Vertical Coordinate measured in some coordinate system associated with Card 1.

Exact Position of Origin of this {X, Y} coordinate system is of no importance for the goals of the present invention.

Other Parameters — Set of parameters that are specific to the practical implementation of the Optical Key Reader 2, for example, power of the White Light Source 10 (Spot Lamp or LED). It is the ultimate goal of the present invention to ensure, that these parameters will have no (or minimal) affect on the operation of the system by means of proper setup, special calibration and auto-calibration procedures (described further).

Fig. 6 schematically illustrates one possible practical implementation of the Unique Optical Key that is physically embedded into optically transparent Card 1. On the surface of the card, Plurality of Small Birefringent Elements and/or Linear Polarizing Elements 26 are scattered in a pseudo random fashion, i.e. size, shape, color, optical orientation and position of each Birefringent Element and that of the Linear Polarizing Elements are pseudo random.

There are a several practical ways of achieving such pseudo random scattering. One exemplary way is: a) Preparing a proper number of sheets of thin transparent plastic which plastic exhibits optical activity (that is rotating plane of polarization). Transparency films used for copy machines or ink-jet printers are good enough for this goal, but any other appropriate thin film may be used. Optionally, prepare polarizing filters implemented as thin plastic films. It is preferable to use a mixture of transparencies of different types. b) Shredding appropriate amount of sheets (by using, for example, rotating blade) into small pieces of pseudo-randomly different sizes and shapes (say of exemplary size of about 0.1 mm or less). c) Spraying (for example using pulverizing gun) color ink on small pieces randomly distributed on some surface. It is preferable to repeat this process several times by using different colors. d) Dispersing randomly the obtained small pieces on the surface of the Card 1 (for example by dropping them from some height in turbulent environment) and an iron such pieces inside the card, thus creating a flat surface. Optionally the surface may be polished and covered by transparent optically inactive protective layer (for example by polyethylene).

At the end of the above process, on the surface of Card 1, Plurality of Small Birefringent Elements and/or Linear Polarizing Elements 26 will be scattered in a pseudo random fashion i.e. size, shape, color, optical orientation, and position of each Birefringent Element and that of the Linear Polarizing Elements will be random, and thus Unique Optical Key with unique optical properties will be created.

It is clear to anyone skilled in the art that such a key can not be duplicated or copied by using reasonable resources and state of the art inexpensive equipment, and thus this key may be considered as unique and as non-forgeable.

It is also clear, that whenever the Unique Optical Key is inserted into the Optical Key Reader 2, then, according to formula [1], for each combination of angles θi and θι different image (set of pixels) will be achieved. Generally speaking, let's assume that angle θj (which may be achieved by using

Rotation Means 14) may be set by sending a number in the range from 0 to 255 (that is byte: Byte #1) to the Rotation Means 14 by utilizing standard electronics elements which are part of the Optical Key Reader 2. In the same fashion angle θz maybe set by sending Byte #2 to the Rotation Means 21.

Let's assume additionally, that Row and Column that are used in Formula [1] may be encoded each by, say, two bytes. This means that by sending a message to the Optical

Key Reader 2, each message containing set of 6 bytes and thus encoding some set of

{θi , Θ₂, Row, Col} - [Request] , Optical Key reader will return one Byte [Response] characterizing Gray level of the corresponding region of the Unique Optical Key. In case that standard true-color Imaging Element is used (which is preferable) a set of three bytes corresponding to basic colors {R, G, B} - [Response] will be returned. It is clear, that for each specific Unique Optical Key specific Request will provide specific Response.

It is clear enough that the number of possible combinations (patterns) is large enough in order to prevent "guessing" attack even for one request.

hi case of sequential requests, the number of total possible combinations will become extremely large, meaning that security level may be custom regulated by varying request' length).

In order to ensure reliable work of the authentication process, it must be ensured that during mass production any properly assembled from standard elements Optical Key Reader 2 will produce the same (or close enough) Response to the same Request sent to the specific Unique Optical Key.

To ensure reliable authentication additional elements (members) and a number of calibration procedures must be added to Optical Key Reader and to Card 1.

Fig. 7 schematically illustrates additional unique optical member: Transparent Unique Member 27 that is integrated into Optical Key reader in order to enable reliable authentication of the specific Optical Card Reader and to provide additional security features (described further). Transparent Unique Member 27 has similar to

Card 1 technical design (that is plurality of optically active elements and, optionally, some calibration markers).

Calibration Procedure of the White Light Source.

hi order to compensate for the differences in position, orientation, power variations and optical characteristics of the White Light Source 10 (optionally Spot Lamp or White LED), the following procedure may be used:

a) Referring to Fig. 3 and Fig. 7 (before Card 1 is inserted), White Light Source 10 is ON and {R, G, B} values of central pixel of the Imaging Element 25 are monitored. Processing Unit 5 operates Rotation Means 14 and 21 until maximum values of {R, G, B} are obtained, meaning that Optical Axes 12 and 22 are, then, nearly parallel.

b) Enable standard auto-brightness and auto-white-balance procedures to run in order to find optimal parameters (such as brightness, contrast, gain control, etc.) for the Imaging Element 25.

c) Disable all automatic controls and store parameters of Imaging Element 25 (such as brightness, contrast, gain control, etc.) in the Processing Unit 5 as Parameters Set #1

d) Grab full image projected to the Imaging Element 25 and store it inside Processing Unit 5 as Image #1.

Image #1 will be used later as reference image providing information about non- homogeneity of spatial distribution of the White Light Source 10. Ideally, all pixels of Image #1 must have equal {R, G, B} values, but practically, central pixels may be brighter than peripheral ones. Additionally (and despite auto-white balance procedure) real colors of the "White" Light Source 10 may be seen as non- white in different regions of Image #1. Such differences are not big, but may appear to be critical for reliable authentication.

First Calibration Procedure of the Rotation Means 14 and 21. In order to create standard interface between Processing Unit 5 and Rotation Means 14 and 21 and in order to eliminate importance of initial positions of mechanical and optical elements of the Optical Key Reader 2, the following calibration procedure may be used:

a) Starting from configuration shown on Fig. 3, rotate First Linear Polarizing Filter 12 clockwise (by sending proper sequence of pulses from Processing Unit 5 through Optical Key Reader 2 to Rotation Means 14) until minimum values {R, G, B} are obtained (meaning that Optical Axes 12 and 22 are nearly perpendicular). Thus a number of pulses required in order to rotate First Linear Polarizing Filter 12 from angle 0° to angle 90° may be evaluated specifically for the current exemplar of Optical Key Reader.

b) Rotate First Linear Polarizing Filter 12 counterclockwise (by sending proper sequence of pulses to Rotation Means 14) until maximum values {R, G, B} are obtained (meaning that Optical Axes 12 and 22 are nearly parallel again). Thus a number of pulses required in order to rotate First Linear Polarizing Filter 12 from angle 90° to angle 0° may be evaluated specifically for the current exemplar of Optical Key Reader. (Ideally, the number of pulses required for rotation from angle 0° to angle 90° should equal to the number of pulses required for rotation from angle 90° to angle 0°, but by utilizing this procedure by a number of times, inaccuracy of mechanical elements of the Optical Key Reader may be evaluated, and thus this procedure maybe considered as accuracy self-test).

After completion of steps a) and b), Processing Unit 5 may create and store proper LUT #1 (Look-Up-Table) which will be used in order to evaluate the number of pulses required in order to rotate First Linear Polarizing Filter 12 to any angle in the range from 0° to 90°. From this moment, sending Byte #1 of specific value to the LUT #1 will rotate First Linear Polarizing Filter 12 by the specific angle known θj, thus eliminating influence of specific mechanical implementation of Rotation Member 14 on Authentication Process. c) Repeat procedure of steps a) and b) for the Second Linear Polarizing Filter 20, thus creating LUT #2.

From this moment on sending sequence of {Byte #1, Byte #2} from the Processing Unit 5 by using Communication Link 4 to the Optical Key Reader 2 will properly set angles θj and 0₂ relative to some axis, exact direction of which remains undefined during this step.

To make Authentication Process reliable, additional means are added to the Unique Optical Key.

Fig. 8 schematically illustrates one possible exemplary implementation of the Unique Optical Key with special zones and markers designed to ensure reliable operation of the Optical Key Reader 2.

Card 1 of Fig. 6, in this implementation, contains additional optically transparent zone (optionally in the top central part of the Card 1): Public ID Zone 28. Some ID either in the human readable form (for example Card Unique Number), or in the machine- readable form (for example bar-code containing Card Unique Number) may be engraved on Public ID zone 28 in such a way, that said ID may be reliably recognized by processing image grabbed by Imaging Element 25 by Processing Unit 5 by using proper OCR procedure. Exact shape, color, orientation and position of this Public ID Zone 28 has no importance to the goals of the present invention while image processing software installed in the Processing Unit 5 may recognize such ID and convert it into a digital form.

Card 1, in this implementation, additionally contains a plurality of optically non- active transparent or semi-transparent markers, hi one possible embodiment, four markers are used: Left Top Card marker 29, Right Top Card Marker 30, Right Bottom Card Marker 31 and Left Bottom Card Marker 32. In one preferred implementation, each marker has different color. Exact positions of these markers are not important while they are positioned close to especially dedicated for such markers zones. The goal of such markers is to compensate for inaccuracy of positioning of

Card 1 relative to Lens 24 and Imaging Element 25.

Card 1, in this implementation, additionally contains Linear Polarizing Element 33 with an easily recognizable shape (for example arrow) pointing (preferably) upwards and positioned in the dedicated region (optionally at the center of the Card 1).

The goal of said Linear Polarizing Element 33 is to calibrate starting positions of Optical Axes 13 and 22 of the First Linear Polarizing Filter 12 and Second Linear Polarizing Filter 20. The exact shape, orientation and position of this Linear

Polarizing Element 33 has no importance for the goals of the present invention while image processing software installed in the Processing Unit 5 can recognize such an element.

Card 1, in this implementation, additionally contains Overlap Zone 34 which is designed to work in coordination with Transparent Unique Member 27.

Fig. 9 schematically illustrates the operation of Optical Key Reader according to the exemplary embodiment of the present invention. Card 1 (according to implementation of Fig. 8) is inserted into the Optical Card Reader (specifically by using Horizontal Guiding Members 16 and 18 until mechanical contact with Vertical Stopper 17). Card 1 must be retained in this position until the end of the authentication process. Insertion and ejection of the Card 1 maybe either manual, or electro-mechanical, i the latter case additional standard means (including insertion and ejection sensors of any appropriate type) must be added.

Before Authentication Process can start, additional calibration procedures are needed in order to compensate for inaccuracy of the insertion of the Card 1 and inaccuracy of mechanical and optical elements of the Optical Card Reader 2.

Public ID Extraction It is assumed, that before insertion of Card 1, Directions of Polarization 13 and 22 are parallel and that optimal parameters of the Imaging Element 25 are properly set. Then, after Card 1 insertion into Optical Key Reader 2, Image #2 is grabbed and stored in the memory of Processing Unit 5. (Any mechanical, optical or other appropriate means may be used to detect the moment of Card insertion in order to initialize

Authentication Process).

Considering the fact, that Public ID Zone 28 exhibits no optical activity, Public ID Number printed in this Public ID Zone 28 will be properly seen on the Image #2. As a result, by using proper OCR procedure, Public ID Number can be extracted and its value in numerical form can be stored in the Processing Unit 5.

The goal of this Public ID Number is to eliminate the need for searching relevant parameters of Unique Optical Key in the Data Base. Here, instead of lengthy search for proper properties set in the Data Base, a much faster direct comparison will be performed thus enabling to achieve fast (practically, real-time) authentication.

The additional goal of this Public ID Number is to provide support for the situations either when there is a malfunction, or when manual authentication is needed.

Card Position Mapping.

Despite the usage of Horizontal Guiding Members 16, 18 and Vertical Stopper 17, position of Card 1 relative to Imaging Element 25 may differ for different reader exemplars, hi order to compensate for this sort of inaccuracy, known to the skilled in the art, 2D Mapping procedure using optically inactive markers 29, 30, 31, 32 will be used:

a) Using extracted earlier Public ID Number, extract from Data Base exact coordinates {X, Y} and {R, G, B} color values and approximate positions {Row, Column} for each of the markers 29, 30, 31, 32.

b) Using Image #2 finalize positions of the markers (using any proper image recognition procedure). To enable fast and reliable mapping shape and color of the markers may be initially chosen specifically for the mapping goals. For example, black rectangle or circle shape may be chosen, center of which on white background may be easily defined with sub-pixel accuracy. Initial {Row, Column} positions of the markers will shorten significantly the time needed to find exact positions of the markers by significantly confining region of search.

c) Using exact values of {X, Y} extracted in the step a) and resulted values of {Row, Column} of the center of each marker obtained in the step b), the following mapping formulas can be created:

R w =F_R0W{X,Y); [2]

Column =F_C0LUMN{X, Y); [3] " ^Mappin^{g Fo} _mu^las.

Any appropriate mathematical parametrical function may be used in order to create practical Mapping Formulas. In the exemplary practical implementation that uses 4 markers, bilinear mapping may be used:

Row =a_n + a_l2 ' X+a_u ' Y+ a_l4 ' X - Y; [4]

Column = a 1"₂J Λ + i~

^*• XY ^* +τ" C al₂₃ ^*• J Y. + I

^■ X • Y ; [5] ^{" Bilinear Mapping}

Coefficients {ai ] ..a₂₄} may be evaluated by using 4 known (after steps a) and b)) associations: {Row, Column} -_> {X, Y}

Then, by using known {X, Y} coordinates of some element on the Card 1 (stored in the Data Base in the Processing unit 5), {Row, Column} values of the same element of the image grabbed by Imaging Element 25 may be calculated by using formulas [4,5] regardless of specific implementation and inaccuracies of the Optical Card Reader 2.

Second Calibration Procedure of the Rotation Means 14 and 21. Exact initial positions of the First and the Second Linear Polarization Filters 12 and 20 can be set by utilizing Linear Polarizing Element 33 embedded into Card 1. Assuming that Directions of Polarization of the First and Second Linear Polarization Filter 13 and 22 are still parallel, First and Second Polarization Filters are simultaneously rotated (say) clockwise while monitoring {R, G, B} values of known pixel of Linear Polarizing Element 33. Position when {R, G, B} values are maximal is considered as starting position with θρ=0 and 0₂=0. In case when extra reliability is needed, LUT #1 and LUT #2 may be recalculated by using Linear Polarizing Element 33 as a reference.

From this moment the following exemplary request may be created:

By sending this request from Processing Unit 5 by using Communication Link 4 to Optical card Reader the following will happen:

- First Linear Polarizing Filter 12 will be rotated clockwise by angle θi - Second Linear Polarizing Filter 20 will be rotated clockwise by angle 0₂ - Imaging Element 25 will grab Image #N and store it temporally in the memory of the Processing Unit. Previously stored Image #1 may optionally be used in order to compensate Uneven Illumination of the White Light Source 10 by using any appropriate and known to the skilled in the art algorithm. - Row and Column of the requested pixel will be calculated by the Processing Unit 5 by using Mapping Formulas [4, 5]. - {R, G, B} values of the pixel having {X, Y} coordinates (Response) will be extracted from the Image #N - and compared (by using proper comparison criteria) with values stored in the data base. - In case of positive comparison result, inserted card will be considered as authentic and Processing Unit 5 will send authorization signal to the Service Provider Unit 7 by using Communication Link 6. In one implementation of the Authentication Protocol, Number N of Requests and Corresponding Responses may be set to some practical number, which number will provide a controlled trade-off between adequate security level (larger N leads to lower chances of successful "guessing" attack, and therefore to better security) and reasonable time required in order to accomplish the test (for large N large number of polarizer's rotations and large numbers of image "grabbing" is required, leading to longer authentication time).

For example, in case of utilizing Authentication Protocol that requires 10 sequential requests, the total number of bits needed for a successful "guessing" attack will be 10*3*8 =240 bits, which is more than enough for a typical secure transaction.

It must be taken into account, that for each transaction, different set of requests will be compiled in a pseudo random way, making random guessing attempts totally impractical.

Assuming, that it would be impractical to store {R, G, B} values for all possible combinations of the angles θj and 0₂ and coordinates [X, Yj, in one possible implementation of the Data Base only small subset of the angles , coordinates and their respective {R, G, B} values will be stored in the Data Base. This feature will not compromise security because the number of all possible requests and responses is still very large for random guessing attack to succeed.

In order to provide better reliability of the authentication protocol, small region (say of circular or rectangular or any other appropriate shape) with known position of its center {X, Y} may be stored as pattern in the Data Base. Then the result of the authentication will be derived as result of pattern comparison between reference pattern stored in the Data Base and currently extracted pattern from specific region of the specific card. Any known to the skilled in the art techniques for pattern comparison may be used, including statistical ones. Thus small variation of the optical properties of the Card and Optical Card Reader will not prevent positive authentication of the valid card, while invalid card having significantly different patterns will still be rejected. In order to provide an analogue of the "slip/iron" procedure, used in the Magnetic Card technology that is used as a proof of manual transaction, Transparent Unique Member 27 is added to Optical Key Reader 2, and Overlap Zone 34 is added to the Card 1. Whenever Card 1 is inserted into Optical Key Reader 2, optical overlap is created between Transparent Unique Member 27 and Overlap Zone 34. Correspondent portion of the Image which is grabbed after setting certain specific values of angles θi and 0₂ may optionally be stored at the Processing Unit 5 as a transaction proof. It is clear to anybody skilled in the art, that creation of such an image without having specific Card and specific Card Reader available at the same place at the same time is practically impossible, and thus such sub-image may be used as a proof of mechanical insertion of the specific Card into Specific Optical Card Reader.

Additionally, Transparent Unique Member 27 may be used as non-forgeable ID of the Optical Key Reader in some additional implementations of the Authentication Protocol.

Fig 10 schematically illustrates the operation of another implementation of the Optical Key Reader modified for reflective Card.

In certain situations, usage of optically transparent Card may be problematic or inappropriate.

In such cases, Card 1 (according to the exemplary implementation illustrated in Fig.6 and Fig. 8) may be produced by using non-transparent base substrate. Unique elements must be embedded to one of the surfaces of such non-transparent substrate. No special modification of the card production equipment is needed, except for proper choice of materials. Plastics that are currently used for the production of most standard magnetic cards are suitable for this goal.

hi this implementation Optical Axis of Incident Light 35 creates some angle with Optical Axis of Reflected Light 36, and positions of the other elements of the Optical Card Reader are modified specifically to the reflectance phenomena. Operation and

Calibration of the reflection-based reader is nearly identical to the transparent-based reader.

Additional option in the configurations presented in the Fig 9 and 10 is that White Light Source 10 is replaced by any appropriate electronically controlled monochromator/spectroscope, thus significantly increasing number of possible combinations, and thus significantly increasing security level.

Additional option for the configurations presented in the Fig 9 and 10 is that First and Second Polarizing filters 12, 20 and their corresponding mechanical Rotation Means 14, 21, are replaced by optically active members polarization properties of which are controlled by changing either Electrical or Magnetic field by using any appropriate electronic means. Advantage of such implementation is that no moving mechanical elements are needed.

Fig 11 schematically illustrates the operation of yet another implementation of the Optical Key Reader 2 (reader apparatus) modified for reflective Card 1 having fixed number of stationary positioned linear Polarization filters (say 39a, 39b, 39c, 39d, 39e and 39f), each filter having specific Direction of Polarization. Proper electronic members of the Optical Card Reader by providing proper switching of White Light Sources (electronically controllable Spot Lamps or white LEDs, say 38a, 38b, 38c, 38d, 38e and 38f) and thus reflected from the card 1 light 37 by passing optional Linear Polarization Filter 40, creates different images on the imaging element 25. Despite the fact that the possible number of combinations in this implementation is less that in the previous implementations, important advantage of such implementation is that no moving mechanical elements are needed, and therefore such design may be considered as the simplest and the cheapest. Additional option in this configuration is to rotate Linear Polarization Filter 40 by utilizing any available controllable rotational means in a manner described earlier. Then, number of possible images of the same card is larger. Such an option maybe useful when reflected variant of the Card is preferred without security compromising. Additional option in the configuration presented in the Fig. 11 is that one of the light sources (for example Light Source 38a) is replaced by Ultraviolet Light Source, and its corresponding polarizing filters (for example First Linear Polarizing Filter 39a) are replaced by transparent to Ultraviolet emission filter, hi this case Card 1 may additionally contain regions that are pseudo-randomly covered by spots of fluorescent dyes of different sizes and fluorescence colors, and thus the number of combinations (and thus possible patterns) will be increased making it increasingly difficult to produce duplicate of this card.

Fig. 12 schematically illustrates main electronic blocks of the authentication system, h one exemplary implementation of the present invention, Optical Key Reader 2 may contain: - Plurality of N (for example 6) Electronically controlled Light Sources 41a, 41b and 41c (for example light sources 38a, 38b, 38c, 38d, 38e, 38f in the reflection configuration of Fig. 11) are switched on/off by utilizing Controller "A" 42. In one preferable implementation of the present invention, Light Sources are LEDs whereas each of those LEDs (or any chosen combination of those LEDs) can be switched ON by applying adequate voltage (of voltages) generated by Controller "A" 42 according to the chosen protocol; - First Polarizing Filter's actuator 43a, and Second Polarizing Filter's Actuator 43b (for example rotation means 14 and 21) are controlled by Controller "B" 44. In one preferable implementation of the present invention, actuators 43a, 43b are stepper motors, operation of which is controlled by sending to them sequences of pulses generated by Controller "B" 44 according to the requested rotation of the relevant polarizing filters; - Imaging Sensor 45 (for example CCD or CMOS image sensor) is controlled by Controller "C" 46, which controller can set relevant parameters of the Imaging Sensor 45 (for example Brightness, Gain) according to the goals of the present invention and convert row data of the said sensor into digital image according to the chosen image format;

- Communication Unit 47 goal of which is to provide communication between Processing Unit 48 and local or remote server 49 by utilizing any appropriate for that purpose protocol;

- Processing unit 48 (for example microprocessor or microcontroller) coordinating operation of controllers 42, 44, 46 and managing communication with the Server 49 by operating Communication Unit 47. h one preferable implementation of the authentication system, all relevant image data concerning initialized cards are stored in the Data Base 50 operated by local or remote Server 49. Any implementation of the blocks 49 and 50 can be chosen, while valid REQUESTS (for example according to the protocol described earlier) can be generated and while RESPONSes received from the Optical Key Reader 2 can be utilized for comparison with those stored in the Data Base 50, thus validating as valid or rejecting as forged pr invalid current card in test.

While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without either departing from the spirit of the invention or exceeding the scope of the claims.

Claims

1. An optical authentication device comprising: a plurality of elements having optical polarizing properties distributed in a pseudo- random manner over a predetermined area; at least three optically detectable markers positioned in predetermined positions with respect to the predetermined area; whereby, when viewing the predetermined area with an optical imaging sensor of a reader under an illumination having specific polarization properties a first image is obtained that is different from one or more other images obtained under one or more illuminations having different polarization properties, thus by comparing two or more images of at least a portion of the device to saved images of the same device or a portion thereof taken under the same illuminations, using the markers for aligning images to be compared, authentication is achieved.

2. The device of claim 1 , further provided with at least one public identification detail that is optically distinguishable in a machine readable form.

3. The device of claim 1 , further provided with at least one additional area containing a plurality of elements having optical polarizing properties distributed in a pseudo-random manner, for validating interaction with a specific reader.

4. The device of claim 1 , wherein at least a portion of each element is fully or partially optically transparent, so as to allow incident illumination to pass through the device.

5. The device of claim 1 , wherein at least a portion of each element is fully or partially optically reflective, so as to allow incident illumination to be reflected from the device.

6. The device of claim 1, wherein at least some of the elements of optical polarizing properties comprise elements changing orientation of polarization of incident illumination of specific polarization orientation.

7. The device of claim 1, wherein at least some of the elements of optical polarizing properties comprise elements exhibiting properties of linear polarization filters.

8. The device of claim 1 , wherein at least one of the elements of optical polarizing properties comprise an element having predetermined shape and position exhibiting properties of linear polarization filters.

9. The device of claim 1, wherein one or more of the elements has its own spectral properties.

10. The device of claim 1 , further provided with one or more fluorescent elements.

11. A reader apparatus for reading the device of claim 1 , the apparatus comprising: a source of a light beam a first polarizer for modifying in a controllable manner the polarization of the light beam; a holder for holding the device in the optical path of the beam; a second polarizer for modifying in a controllable manner the polarization of the light beam after it passes through or reflected from the device; a controller for controlling the first polarizer or the second polarizer or both; an optical imaging sensor for obtaining different images of the device in different polarization orientations of the first polarizer or the second polarizer or both; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison.

12. The apparatus of claim 11, wherein the holder further comprises an additional area comprising a plurality of elements having optical polarizing properties distributed in a pseudo-random manner, wherein at least a portion of each element is fully or partially optically transparent, for validating interaction with a specific optical authentication device.

13. A reader apparatus for reading the device of claim 1 , the apparatus comprising: a plurality of controllable sources of light beams each source having its own polarizer for polarizing its light beam in a predetermined polarization orientation; a holder for holding the device in the optical paths of the beams; a controller for controlling separately or in combinations said plurality of controllable sources of light beams; an optical imaging sensor for obtaining different reflected images of the device illuminated by a chosen combination of one or more light beams of said plurality of controllable sources of light beams; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison.

14. The apparatus of claim 13, wherein the holder further comprises an additional area comprising a plurality of elements having optical polarizing properties distributed in a pseudo-random manner, wherein at least a portion of each element is fully or partially optically transparent, for validating interaction with a specific optical authentication device.

15. The apparatus of claim 13 , further provided with a controllable polarizer filter positioned between the holder and the optical imaging sensor.

16. The apparatus of claim 13 , further provided with one or more ultraviolet illumination sources for illuminating the device and detecting fluorescent elements.

17. The apparatus of claim 13, further provided with one or more illumination sources each having its own filter having predetermined spectral properties.

18. The apparatus of claim 13 , wherein one or more of the polarizers has its own predetermined spectral properties.

19. A method for authentication comprising: providing a reader apparatus comprising: a source of a light beam; a first polarizer for modifying in a controllable manner the polarization of the light beam; a holder for holding a device to be authenticated and in the optical path of the beam; a second polarizer for modifying in a controllable manner the polarization of the light beam after it passes through or reflected from the device; a controller for controlling the first polarizer or the second polarizer or both; an optical imaging sensor; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison; placing the device on the holder and obtaining different images of the device in different polarization orientations of the first polarizer or the second polarizer or both; comparing the obtained images with image information stored in a database of optical authentication devices, each device comprising: a plurality of elements having optical polarizing properties distributed in a pseudo-random manner over a predetermined area; at least three optically detectable markers positioned in predetermined positions with respect to the predetermined area authenticating the device if the obtained images match or are close enough to stored images of a device, or rejecting the device if differences larger than a predetermined level are found.

20. The method of claim 19, further comprising providing a public identification detail to each device to be authenticated and using the same public identification detail when comparing the obtained images with image information in the database.

21. A method for authentication comprising: providing a reader apparatus comprising: a plurality of controllable sources of light beams each source having its own polarizer for polarizing its light beam in a predetermined polarization orientation; a holder for holding the device in the optical paths of the beams; a controller for controlling separately or in combinations said plurality of controllable sources of light beams; an optical imaging sensor; a communication unit for communicating with a local or remote server unit having a database containing information relating to images of relevant optical authentication devices or portions thereof for comparison; placing the device on the holder and obtaining different reflected images of the device illuminated by a chosen combination of one or more light beams of said plurality of controllable sources of light beams different polarization orientations of the first polarizer or the second polarizer or both; comparing the obtained images with image information stored in a database of optical authentication devices, each device comprising: a plurality of elements having optical polarizing properties distributed in a pseudo-random manner over a predetermined area; at least three optically detectable markers positioned in predetermined positions with respect to the predetermined area authenticating the device if the obtained images match or are close enough to stored images of a device, or rejecting the device if differences larger than a predetermined level are found.

22. The method of claim 21 , further comprising providing a public identification detail to each device to be authenticated and using the same public identification detail when comparing the obtained images with image information in the database.