WO2014080214A1

WO2014080214A1 - A machine-readable tag and a reader and system for use with the tag

Info

Publication number: WO2014080214A1
Application number: PCT/GB2013/053087
Authority: WO
Inventors: Andrew Stephen Leyland CRAMMOND; Graham Bell; Morgan ATKINS; Kurt Paul MORGAN
Original assignee: Pa Knowledge Limited
Priority date: 2012-11-23
Filing date: 2013-11-22
Publication date: 2014-05-30
Also published as: GB201221127D0

Abstract

A machine-readable tag having a readable secure key embedded therein, the tag being configured to change the secure key automatically in response to at least one external factor and a system for use with the tag including a clock configured to provide information indicating the current time, a memory storing information regarding valid secure keys correlated with time, and a processor configured to compare information read from a tag with said information stored in the memory for the time of reading and to validate the tag when said information read from the tag is in accordance with said information stored in the memory.

Description

A Machine-Readable Tag and a Reader and Sys

The present invention relates to a machine-readable tag and also a reader and a system for use with that tag, in particular a tag having a readable secure key embedded therein to be read by the reader and system for validation to authenticate any item supplied with the tag or for use as part of a lottery.

The QR code (Quick Read code) developed by Denso Wave initially for the automotive sector is now in use for a variety of applications. Barcodes are also known.

A QR code is made up of a number of pixels in a known structure - typically a 2D matrix. The matrix is composed of pixel elements depending on the encoded data - which may also include error protection. More information on QR codes can be found at:

http://www.qrcode.com/en/index.html

Typically the QR Code is used to embed / encode information such as a URL to a website. The QR code is then printed on business cards or posters allowing a viewer / user to scan the QR code with a portable terminal, typically a mobile phone running a QR reader application. The QR application interprets the QR code and recovers the embedded information. Where this is a URL to a website, the QR reader application can link the user to the target website.

Barcodes and QR codes have many advantages in terms of providing a machine readable format for transfer of data to a user's terminal device. One disadvantage of the barcode and the QR code is that it can be copied. Barcodes and QR codes can be scanned, photographed and reproduced using consumer grade printers. The technology is therefore not appropriate for applications requiring authentication, or other secure transfers of data. It is therefore an object of the present invention to at least reduce the problem of authentication tags being copied and to provide improved means for validation/authentication. According to the present invention, there is provided a method of preventing or controlling unauthorised copying of a machine-readable tag, the method including changing machine- readable codes in the tag on the basis of time or some other variable, the machine readable codes incorporating an element of a secure key. A plurality of machine-readable tags may be provided as a set to be secured together to a single item for authentication.

According to the present invention, there is also provided a method for providing lottery codes including providing a machine-readable tag, having machine-readable codes in the tag which change on the basis of time or some other variable, the machine-readable codes incorporating the lottery codes.

The present invention also provides a machine-readable tag, a reader and a system for use as part of that method.

According to the present invention, there is provided a machine-readable tag having a readable secure key embedded therein, the tag being configured to change the secure key automatically in response to at least one external factor.

In this way, because the secure key changes, it is not possible for it to be copied by a third party. In other words, if a third party copies the secure key at any particular instance, then subsequently when a consumer comes to validate the copied key so as to authenticate a product, etc, the copied key will not have changed as expected and will not be validated. The external factor can include exposure to light, one or mo

electromagnetic energy or other stimulus. However, preferably, the external factor is time and the tag is configured to change the secure key in response to the passing of a predetermined time. In this way, after the predetermined time, any validation process will expect the secure key to have changed in an expected or predetermined manner and validation can take place on the basis of the new version of the secure key. If the secure key has not changed as expected, then validation will not occur. In some embodiments, the tag may be configured to change the secure key successively with the passing of respective ones of a plurality of time intervals.

In this way, even if a third party attempts to copy the tag and secure key after a first

predetermined time interval, a genuine secure key will be expected to change again before the actual time of validation.

The tag may include readable parts configured to convey respective pieces of information according to their respective properties, wherein at least some of the parts are configured to change their respective properties in response to the at least one external factor so as to change the respective conveyed pieces of information.

In other words, the secure key may be provided as a plurality of individual pieces of information and one or more of those pieces of information may be set to change automatically so as to change the secure key as a whole. In this respect, each changeable piece of information can be configured to change at the expected time intervals or, alternatively, different respective individual pieces of information can be configured to change at longer time intervals, but staggered with respect to each other so as to provide a secure key which as a whole changes with the expected time intervals. The tag may be configured to provide the readable secure key as a radio signal. For example, the tag may be an RFID. In this respect, parts of the tag may be configured to change with the external factor so as to change the secure key provided in the radio signal.

The chemical properties of the at least some of the parts may be configured to change over time.

Appropriate materials for providing colour changing properties as such will be known to persons skilled in the art. For example, the chemical colour change processes used on time-expiry visitor badges, as supplied by Transtech Systems are an example of this kind of time based colour change. In one arrangement, at least some parts of the tag may be printed with such colour changing inks such that the corresponding visual appearance of the tag changes dueto the influence of external factors on the inks. The changing chemical properties may be read in any known manner and could result in corresponding changes in electrical properties, for example to be read directly as electrical information or changing the overall secure key, for instance provided as a radio signal.

In some embodiments, the tag may include an electronic display configured to display at least the at least some of the parts and to change the visual appearance of the at least some of the parts over time.

Any known type of display, such as an LCD, could be used to provide some or all of the pieces of information conveying the secure key. The tag may be pre-programmed to change the display according to passing time intervals.

The readable parts may be together provided as a readable image conveying the plurality of pieces of information of the readable parts. This can be achieved by using a device such as an electronic display or alternatively by using printed information that changes over time according to chemical properties of the at least some of the parts.

Similarly, the readable image may change according to other external factors, such as heat. The chemical properties can similarly change so as to change the readable image.

The readable image may be provided as a barcode or a QR code.

The at least some of the parts may be configured to change in one or both of shade and colour.

The image may be visible to a machine not only within the spectrum of light visible to the human eye, but also in other bands, such as infrared and ultraviolet.

In a further embodiment, the secure code may be represented by at least one modulated source of light. Data modulated onto at least one localised source may be used to represent the secure code. The bitstream(s) may be detected and decoded using camera or photo-detector technology. Multiple sources and or colours may be used to reduce the transmission time.

The machine readable tag has been explained as optionally including a plurality of readable parts, some of which may change in response to the at least one external factor. However, the number of parts can be reduced to only a small number of parts which are modulated in some way so as to provide the information for the readable secure key. In response to the external factor, the modulation can change so as to provide different information. Indeed, it is possible to provide the machine readable tag with only one readable part which is configured to convey information and which is configured to change the information in response to the at least one external factor. The readable part may be provided as a modulated source of light, for example emitting or reflecting light. The readable part may comprise one of a light emitting and a light reflecting element configured to convey the information by a sequence of intensity and/or wavelength changes.

In other words, the readable part may provide a sequence of pulses (on/off or flashes) conveying the information for the secure key. In response to the at least one external factor, the sequence may change to provide different information for a different key.

Alternatively or in addition to the pulsed sequence of intensity, the readable part may convey the information by a sequence of wavelength changes, in other words changing in colour.

In order to reduce a required sequence length and, thereby, reduce any transmission time, plurality of such readable parts can be provided.

The readable part can be provided as a light source, such as an LED or illuminated LCD element. Alternatively, it could be provided as an element with variable pigmentation or reflectivity, such as an LCD or controllable mirror.

Where the present invention is to be used in conjunction with a large product, such as a shipping container, it may be desirable to provide a set of machine readable tags to be secured together on that product.

Each machine readable tag of the set may have its own respective secure key and change in its own respective way, possibly at different respective time intervals. In one preferred embodiment, at least two of the machine readable tags of the set are responsive to different external factors. For example, one machine readable tag e

to a temperature change and another machine readable tag of the same set may change the secure key in response to humidity change. It will be understood that such a set makes the task of faking authentication significantly more difficult.

According to the present invention, there may also be provided a reader for use with a machine- readable tag and configured to read the secure key and validate the tag against time information available to the reader.

In this way, a user may present a tag to the reader for validation. If the tag includes the secure key which has correctly changed in response to the at least one external factor, the tag will be validated, thereby allowing authentication of any item associated with the tag.

The reader preferably includes any appropriate means to obtain the secure key, for instance reading light (visible or other bands), electrical signals or radio waves.

In one preferred embodiment, the reader includes an imaging device configured to provide an image of the tag having the readable secure key and an extraction device configured to obtain the secure key from the image.

In this way, the reader is able to confirm whether or not the read secure key is correct and can be validated.

The reader may include a user interface configured to display whether or not a tag is valid. The reader may include a clock configured to provide inforr

may also be provided with a memory storing information regarding valid secure keys correlated with time. In other words, information is provided for each expected and predetermined time interval, that information indicating the expected secure key for the respective time interval. The reader may also include a processor configured to compare information read from a tag with the information stored in the memory for the time of reading and to validate the tag when the information read from the tag is in accordance with the information stored in the memory.

According to the present invention, there may be provided a system for use with a tag, the system configured to read the secure key and validate the tag against time information available to the reader.

The reader may be a reader as explained above. Alternatively, not all of the features of the reader described above need be provided in the reader itself.

The system as a whole preferably includes a clock configured to provide information indicating the current time and a memory storing information regarding valid secure keys correlated with time. The system preferably also includes a processor configured to compare information read from a tag with the information stored in the memory for the time of reading and to validate the tag when the information read from the tag is in accordance with information stored in the memory. In one embodiment, at least the memory is provided in a database remote from the reader. The memory and the reader may be configured to communicate with each other so as to validate the tag. Of course, it is also possible for the clock and the processor to be provided remotely from the reader. In one application, such as for use with consumer products, the machine readable tag may be configured to change at least some part of the readable image with the passing of respective ones of a plurality of time intervals. These time intervals may be small, for example a few seconds, to provide the secure, copy-proof image and also provide evidence to the consumer (the user) seeing that at lease some part of the readable image is changing, that the authentication system is in place.

In another application, the need for such rapid changing of the at least some part of the image may be unnecessary. For example if the system is used to authenticate parts within a supply chain where parts of transported by ship, there may be no need for the image to change rapidly and hence the time interval may be set to a number of days or even weeks.

In another application, the security of the supply chain may be based on other external factors rather than time. For example the supplier may wish to ensure that the parts are exposed to a controlled humidity, or temperature. Elements of the readable image can be configured to react to humidity, temperature or other external factors such that the expected characteristics of the supply chain can be later confirmed through inspection of the resulting readable image. In another example, the external factor may be the interaction of another entity in the supply chain. For example, the original supplier may establish a secure key for the readable image, which is only modified through interaction with at least one intermediary in the supply chain, for example a port inspector, or shipping authority. This at least one intermediary has the ability to interact with the tag such that at least some parts of the readable image are modified. This interaction may be either electronic or chemical. The interaction indicates that the shipment has successfully passed through that point in the supply chain. This allows the receiving user to check that the shipment has transited through the expect route through the supply chain and hence have confidence that the shipment is authentic. According to the present invention, there may also be provided a system in which machine readable codes are changed on the basis of time or some other variable and which incorporate an element of a secure key.

According to the present invention, there may also be provided a reader which is able to check the machine readable code and validate it against its own knowledge of time, and of the secure key. According to the present invention, there may also be provided a system which uses electronic processing and one or more electronic displays to create the changing codes for such a system.

According to the present invention, there may also be provided a system which uses other electronic or electromagnetic transmission or coding systems to pass such changing information to a reader/receiver.

According to the present invention, there may also be provided a system which uses chemical processes to generate codes which change over time, or in response to exposure to light or other chemical agent or heat or electromagnetic energy or other stimulus.

According to the present invention, there may also be provided a system using the confirmation of correct codes as the basis of product authentication.

According to the present invention, there may also be provided a system using changing codes as the basis of a lottery or advertising medium. According to the present invention, there may also be pro vie

of changing a visible code or representation, as a way of preventing or controlling unauthorised copying. The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which:

Figure 1 illustrates schematically a system embodying the present invention; Figure 2 illustrates schematically functional blocks of a system embodying the present invention;

Figure 3(a), (b) and (c) illustrate a heat changing QR code according to the present invention;

Figure 4 illustrates a tag in use on a product;

Figure 5 illustrates a tag in use on a product;

Figure 6 illustrates a tag embodied in an electronic module; Figure 7 illustrates a tag having a single source; and

Figures 8(a) and (b) illustrate a reader for use with the present invention.

The present invention relates to a method for displaying information code on a display device where a transaction, such as commercial transaction, is to be authenticated by the information code whereby the code changes with some variable, such as time, such that the code cannot be easily copied. The invention can overcome the inherent security issue asso

the concepts of tokens. In the general IT world, secure tokens are commonly used for accessing secure services. One such example is the use of a numeric token for accessing corporate VPNs, or online banking services. These tokens rely on an algorithm generating an apparently random number either automatically (periodically, e.g. every 30 seconds) or in response to a user input. The invention provides a Dynamic QR code that changes over time. This can be embodied, for example, as:

An electronic based system where a display such as a LCD screen or electronic ink screen displays a QR code that automatically changes every n seconds.

A chemical version, where a predefined number of the QR code pixels change over time, e.g. the colour fades due to exposure to an external influence such as light or heat or through some other chemical effect

The relationship to time means that the correct QR code must be displayed at the correct time. Hence the Dynamic QR code cannot be copied as the copied code is only valid for a short (predefined time period). The exact timing of the change is dependent on the nature of the application. For example shipping an item from China to the UK and using a Dynamic QR code for logistics

authentication may only require one change over a two week period. A Dynamic QR code used for authenticating onto an on line server may be required to change every 30 seconds. An important feature of the invention is the dynamic nature of the code, rather than the specific embodiments or applications.

As for "Normal" QR codes, the Dynamic QR code can be read by a QR code reader. The information in the code can then be validated against an application that is in some way aware of the relationship in time and is hence able to validate the Dyi

code is displayed at the appropriate time.

Machine readable tags include a range of technologies often collectively referred to as barcodes such as ID barcodes where data is represented by a plurality of parallel lines of varying widths and spacings; 2D barcodes which utilize rectangles, dots, hexagons and other geometric patterns in two dimensions to represent the data. Known forms of 2D codes include Aqztec Codes (International Standard ISO/IEC 24778), Data Matrix (ISO/IEC 16022), MaxiCode, QR codes and many other variations.

While we use the term QR code it is obvious to those skilled in the art that this system can be applied to any static machine readable tag system.

The basic system, as illustrated schematically in Figure 1, involves the use of a changing machine readable code 2 to indicate a state of validity of an item to which it is affixed. In one manifestation the changeable code is in the form of an electrically changed QR code. In another form this might be an electrically changing linear bar code. In a further manifestation this might be an electronic form of signal such as a radio signal including but not limited to an RFID signal. The optical signals (QR code, bar code or similar formats) may be made in the visible light range or in UV or infrared or in other spectral ranges. Likewise they may include variations in spectral properties (eg colours) to provide further differentiation.

In use the code can be changed at a rate suited to the application.

A reader 4, such as illustrated schematically in Figure 1, is used by a person who wishes to interrogate the data. The reader 4, as well as decoding the basic format of the code 2, is able to analyse the code 2 in order to determine the required validity. The analysis may be based on a parameter which is available to both systems (the code generator 2 and the reader 4), such as time. In this process the reader 4 checks that the code 2 being displayed is appropriate for this current moment in time, allowing for some small variation in record keeping (ie clocks running fast or slow).

Furthermore, the code 2 may incorporate an element which is known only to the code generator and to the reader application. This "key" is analogous to the secret key passed in cryptographic systems. In this case, the reader application is able to check that a) the code is correct with respect to time, and b) the code is correct in accordance with the expected secret key. This then provides authentication of the code.

In operation, such a system may be used to authenticate products. Affixed to a product, the use of the code indicates that the product was authenticated by the vendor (according to the secret key) and has not been counterfeited or otherwise created outside of the control of the authentic vendor.

In a further form, the authentication may be performed by the reader 4 making a remote enquiry to a database 6, perhaps via some wired or wireless link. In this case a similar level of authentication may be achieved, plus also it is possible to obtain authenticated data about the history of the product (for example that it has been sold once already, or

used/installed/commissioned once already).

The changing code 2 can also be used in areas outside of authentication, but which require an element of randomness or selection. An example is in the creation of a form of lottery. The code is presented to users who scan it (with a different application) in order to discover if they have won a prize or been awarded some reward. The code generator is required to manage an appropriate lottery algorithm. The scanner can identify if it has "seen" a winning number or not. Such lottery systems are commonplace on consumer products where customers are encouraged to enter secure codes found on or inside packaging. Example of such lotteries can be found inside crisp packets or cereal boxes where the secure codes are typically alphanumeric codes printed on the packaging. Product owners use such lottery schemes to increase brand awareness through engagement with customers. These schemes however are limited to single interactions due to the static nature of the secure code. An application of the system allows product owners to increase the interaction with products using the fact that the secure code is able to change due to an external factor such as time. This has particular benefits for products that may not otherwise be engaged with on a regular basis by consumers (users), for example cleaning products or automotive spares (such as oil). The changing nature of the code means that consumers (users) can be enticed to re-try the lottery attempt by entering the changing secure code on a more regular basis. An additional benefit of this application, outside or in addition to authentication, is that the interaction with the readable tag allows the product owner to direct the user to additional technical information related to the product. When consumers (users) re-try the lottery they may be directed to product information, for example on the company's website. The technical information may be used to inform the consumers (users) of any new advice or safety warnings (such as product recalls) linked to that product or marketing material appropriate to the product or related products.

In a further implementation of the system, the changing codes 2 may be generated by nonelectronic means. A chemical process which provides colour changes in accordance with time or possibly in accordance with exposure to air or light or some other stimulus, may be chosen and will provide a more limited form of changes. Alternatively, such a chemical process may be used to indicate which of several pre-prepared (but static) codes are currently valid. As noted above, Figure 1 illustrates schematically a system

In particular, a code 2 changes in response to an external factor, such as time. A reader 4 reads the code 2 and optionally checks against a remote database 6. The system, perhaps the reader 4 itself, is able to decode the code 2 and analyse it against locally held time and against a code key.

Figure 2 illustrates schematically functional features of the system.

A detector 12 reads information from a tag 10. As explained above, the tag 10 could provide embedded codes and secure keys in many different ways, such as optically, electrically or with radio waves. In one preferred embodiment, the detector 12 operates as an imaging device for capturing an optical image provided by the tag 10. The imaging device may include some form of scanner, for instance using laser light for scanning barcodes. In one preferred embodiment, the imaging device of the detector 12 may include components of a digital camera for capturing an image. Indeed, the reader 4 may be provided as part of a smartphone and the detector 12 may be provided as part of the smartphone, for example its camera, near field detection components and suchlike.

An extraction device 14, which may be provided as a function of the general processor, functions to extract the readable secure key from the information or signal obtained by the detector 12. The resulting secure key can then be checked by a processor 16 for validation.

In the illustrated embodiment, the processor 16 is provided in communication with a memory 18 and a clock 20. The memory 18 stores information correlating expected secure keys against time. By referring to the current time as provided by the clock 20, the processor 16 can obtain from the memory 18, the expected secure key for the current time. With this information and in any known manner, for instance using tokens, the processor 16 can confirm whether or not the secure key obtained from the tag 10 is valid or not. As illustrated, a user interface 22 is provided. This is configured to provide information to the user indicating whether or not the tag, as read, is valid or not. The user interface could merely include indictors, such as red/green lights or a buzzer, to indicate validation to a user.

Alternatively, the user interface could include a display for presenting more detailed information. Indeed, such a display could be provided on the reader 4 and, where the reader 4 is provided as a smartphone, the screen of the smartphone could provide the display.

It is possible for all of the parts of the system to be provided within a reader. However, in preferred embodiments, at least the memory 18 is provided in an external database as illustrated in Figure 1. The remaining parts of the system could then be provided in a reader 4, for example as part of a smartphone.

The tag can provide the secure key in various alternative ways, for instance as a radio signal (eg from an RFID) or an electrical signal. In certain preferred embodiments, the secure key may be provided as an image readable in wavelengths visible to the human eye or infrared/ultraviolet wavelengths. Possible images can include barcodes and QR codes.

Figures 3(a), (b) and (c) illustrate a secure key provided in an image formed as a QR code 30.

In accordance with the present invention, the QR code 30 may originally have the form illustrated in Figure 3(a). Gradually over time, or after a predetermined discrete time, one or more elements 32 of the QR code change, as illustrated in Figure 3(b). As a result, the secure key presented by the QR code 30 changes.

How the QR code changes with time is predetermined and known to the system such that the system can expect the new secure key as presented in the QR code of Figure 3(b). As a result, even if a third party is able to copy the original QR code 30 of the tag 10, when a user comes to validate the tag 10, the QR code 30 will have changed in a n

third party.

In the illustrated embodiment, over a further period of time, the same or different elements 34 of the QR code 30 can change as illustrated in Figure 3(c). This may be used to validate the tag at different stages and/or make copying by a third party more difficult. The tag 10 may be provided as a printed image to be secured to a product (or printed directly on that product), for example as illustrated in Figure 4. The properties of the materials used to produce the tag, for example the dyes used for the elements 32, 34 can be arranged to change with time, heat, exposure to light, etc. In this way, the QR code 30 changes as illustrated in Figures 3(a), (b) and (C).

In another embodiment, the tag 10 may be provided as an electronic module 40 having a screen 42 for displaying an image including the secure key, for example the QR code of Figures 3(a), (b) and (c).

Figure 5 illustrates such a module 40 attached to a product. Figure 6 illustrates the module 40 with a screen 42. The module 40 includes appropriate hardware and software components, together with an appropriate power source, to display on the screen 42 an image including the secure key and to change that image (and the resulting secure key) over time. The image may be continuously displayed or could be triggered to display when appropriate.

It will be appreciated that each pixel of the QR code described above can be considered to be an individual readable part for conveying information relating to the secure key. It is possible to reduce the number of those pixels (and, hence, readable parts) so that the conveyed information is also reduced. However, each pixel can be arranged to provide information as a sequence, for example modulated by means of intensity and/or colour. In the simplest form, a pixel could flash on and off in a sequence so as to convey particular infi

flash with a different sequence to convey changed information.

The number of pixels may be reduced to only one. With such embodiments, the machine readable tag comprises a single readable part configured to convey information. The readable part may comprise a light emitting or light reflecting element which is modulated so as to convey the required information.

Figure 7 illustrates an embodiment of the present information with a module 44 for attachment to a product. In the illustrated embodiment, the module 44 is provided with a light source 46 such as an LED. The module 44 is configured to operate the light source 46 to provide light which is modulated with a sequence that conveys particular information. In response to external factors, such as time, the module 44 acts to change the information by providing a new appropriate sequence. The light source may be modulate according to intensity and/or

frequency/wavelength.

Figures 8(a) and (b) illustrate schematically a reader 4 embodied in a device such as a smartphone. As illustrated, the reader 4 includes a camera 50 operating as a detector 12 to capture an image. Additionally or alternatively, the reader 4 could include features for receiving a radio signal or include a near field device. In this way, signals including the secure key can be obtained. The images or received signals can be processed to obtain the secure key. The reader 4 can include appropriate software and hardware components to extract and obtain the secure key.

Alternatively, the reader 4 could provide the received/captured information/image and forward this to a remote system/server for processing. In the illustrated embodiment, the reader 4 includes a displa

interface 22. This can provide a user with access to the functionality of the reader 4 and may also provide the user with a display as to whether or not a read tag is valid or not.

Claims

1. A machine-readable tag having a readable secure key embedded therein, the tag being configured to change the secure key automatically in response to at least one external factor.

2. A machine-readable tag according to claim 1 wherein the external factor is time and the tag is configured to change the secure key in response to the passing of a predetermined time.

3. A machine-readable tag according to claim 2 wherein the tag is configured to change the secure key successively with the passing of respective ones of a plurality of time intervals.

4. A machine readable tag according to claim 1, 2 or 3, including a readable part configured to convey information and configured to change the information in response to the at least one external factor.

5. A machine readable tag according to claim 4, wherein the readable part comprises one of a light emitting and light reflecting element configured to convey the information by a sequence of intensity and/or wavelength changes.

6. A machine-readable tag according to claim 4 including a plurality of readable parts configured to convey respective pieces of information according to their respective properties wherein at least some of said parts are configured to change their respective properties in response to the at least one external factor so as to change the respective conveyed pieces of information.

7. A machine-readable tag according to claim 6 wherein the chemical properties of said at least some of said parts are configured to change over time.

8. A machine-readable tag according to claim 6 includ

to display said at least some of said parts and to change the visual appearance of said at least some of said parts over time.

9. A machine-readable tag according to claim 6, 7 or 8 wherein the readable parts are together provided as a readable image conveying the plurality of pieces of information of the readable parts.

10. A machine-readable tag according to claim 9 wherein the readable image is provided as at least one of a barcode and a QR code.

11. A machine-readable tag according to any one of claims 6 to 10 wherein said at least some of said parts are configured to change in one or both of shade and colour.

12. A machine-readable tag according to any one of claims 1 to 4 and 6 wherein the tag is configured to provide the readable secure key as a radio signal.

13. A set of machine readable tags according to any preceding claim, configured to be secured together on a single item.

14. A set according to claim 13, wherein at least two of the machine readable tags of the set are responsive to different external factors.

15. A reader for use with a machine-readable tag according to any one of claims 1 to 12 and configured to read the secure key and validate the tag against time information available to the reader.

16. A reader according to claim 15 including an imagin

image of the tag having the readable secure key and an extraction device configured to obtain the secure key from the image.

17. A machine-readable tag according to claim 15 or 16 including a user interface configured to display whether or not a tag is valid.

18. A reader according to claim 15, 16 or 17 including:

a clock configured to provide information indicating the current time;

a memory storing information regarding valid secure keys correlated with time; and a processor configured to compare information read from a tag with said information stored in the memory for the time of reading and to validate the tag when said information read from the tag is in accordance with said information stored in the memory.

19. A system for use with a machine-readable tag according to any one of claims 1 to 12.

20. A system according to claim 19 including a reader according to claim 15, 16 or 17.

21. A system according to claim 20 including:

a clock configured to provide information indicating the current time;

22. A system according to claim 21 wherein:

at least the memory is provided in a database remote from the reader; and the memory and the reader are configured to commi

the tag.

23. A method of preventing or controlling unauthorised copying of a machine-readable tag, the method including changing machine-readable codes in the tag on the basis of time or some other variable, the machine readable codes incorporating an element of a secure key.

24. The method of claim 23 implemented using a machine-readable tag according to any one of claims 1 to 12 or a set according to claim 13 or 14, together with a reader according to any one of claims 15 to 18 or a system according to any one of claims 19 to 22.

25. A method of authenticating a product including securing a machine readable tag according to any one of claims 1 to 12 or a set according to claim 13 or 14 onto the product.