WO2012110897A2

WO2012110897A2 - Verifying the location of a mobile communication device

Info

Publication number: WO2012110897A2
Application number: PCT/IB2012/000523
Authority: WO
Inventors: Shlomo PERETZ
Original assignee: Peretz Shlomo
Priority date: 2011-02-17
Filing date: 2012-02-17
Publication date: 2012-08-23
Also published as: WO2012110897A3

Abstract

A system for verifying the presence of a mobile communication device (MCD) at a physical site, the system comprising an on-site computing device (OSD) and a remote verification server (VS), the server being communicative with the OSD and with the MCD, wherein - - the OSD has associated therewith a unique identification code and a unique encryption key and is operative to measure elapsed time from a reference time, to generate a site message that contains (a) a current value of the elapsed time, encrypted according to the encryption key, and (b) the identification code and to make the site message available to the MCD while, and only while, the MCD is present at the site; - the MCD, while present at the site, is operative to obtain the site message from the OSD and to send it to the VS; and - the VS is operative, upon receiving a site message from the MCD, to decrypt the elapsed time value contained therein and to check its validity.

Description

SPECIFICATION FOR PCT INTERNATIONAL APPLICATION

TITLE: Verifying the location of a mobile communication device

INVENTOR: Shlomo Peretz

This application claims priority from US Provisional Patent Application No. 61/443,771, filed February 17, 2011 under the title "Sending information to a communication device, based on its verified location".

TECHNICAL FIELD

The field of the invention is retail electronic commerce and in particular - the involvement of inter-device communication in such commerce .

BACKGROUND

In the course of retail commerce that is based on electronic means, such as the Internet, there are often situations in which the realization of a transaction takes place at a specific site, with the presence of the customer, and there is a need to prove the validity of the prior steps of the transaction and to terminate the validity after its realization.

For example, at the current state of art, when a customer acquires over the Internet, a coupon for particular goods or service, and wants to redeem the coupon at a site that offer the goods or service, he may print the coupon or copy it on to his mobile digital device (e.g. cellular phone or tablet computer) and present it at the site; the vendor (i.e. the person in charge of allowing the releasing of the goods or the service to the customer) would then check the validity of the coupon, possibly using a code included therein, note its use (to cancel its validity) and cause the goods or service to be released. This method has several drawbacks: First, in the case of printing, there is a waste of paper and the necessity to remember to carry it to the site; secondly, the method involves several manual operations - by both the customer and the vendor. The second drawback applies also for the case that the customer obtains the coupon as a message (e.g. SMS) on his cellular telephone. For the use with a mobile digital device (such as cellular telephone), a coupon may include a barcode, to be displayed on the device and scanned by a merchant's device; such a method has the drawback that the display quality of particular mobile devices may not be sufficient for such use. Another current method for carrying a coupon in a mobile digital device is to provide it with a suitable application program that can communicate with both the issuer of the coupon and the merchant's device; such a method has the drawback that there are no standards for such a program - making it necessary to acquire and use a multiplicity of such programs and making their use awkward.

As another example, when a customer, after acquiring, over the Internet or through a telephone, tickets to a theater, appears at the theater, he would currently turn to a dispensing terminal, disposed there, and present an identifying card (e.g. a credit card), upon which the terminal, upon approval from a server, would dispense the tickets. This method has the drawback that such terminals are dedicated devices and generally prone to breakdowns - rendering them relatively uneconomic to run.

Thus current methods and systems for concluding electronically arranged transactions upon the presence of the customer at the relevant site are unsatisfactory and there is therefore a clear need for a method and a system that would enable conclusions of transactions at the site with minimum intervention by the customer and by the vendor and using commonly available devices.

There are also other types of situations, in the course of retail commerce that is based on electronic means, that require convenient and economic verification of the presence of a person at a site, such as, for example, the need of an advertising agency to verify that a person has responded to a particular promotion by visiting a relevant site. In many situations it is necessary, furthermore, to verify that such presence of the person is during a particular time period.

SUMMARY OF THE INVENTION

The objective of the present invention is to enable verifying the presence of a person at a given physical site, using commonly available digital devices. Another objective of the invention is to enable verifying the presence of the person at the site during a particular time period and sending to him information that is relevant to that site and that time period.

The present invention is of a system and a method to meet the above stated objectives by means of a mobile communication device (MCD), assumed to be carried by the person, that has data processing capabilities and is operative to run digital application programs and to communicate with a remote server.

According to the present invention, there is provided at each relevant site a so-called On-Site Device (OSD), which may be any device having computing capabilities and the facility to communicate with a remote server over the Internet and/or over a cellular network. The OSD is operative to generate a so-called Site Message that is unique to that site and valid only over a current time period of predefined length and to send it, encrypted, to any nearby MCD. The Site Message generally changes from one time period to another and includes a unique identification code of the particular OSD (referred to as Site ID) and an encrypted version of the value of the current time period, whose start is measured from a given reference time.. The key for the encryption of the time value is preferably unique to each OSD, so as to assure authenticity of its identification during the verification process. In some configurations of the system, the site message, along with the site ID, is preferably formatted together as a

Universal Resource Locator (URL).

Depending on the configuration and embodiment of the OSD, any of a variety of means may serve for sending the Site Message from the OSD to the MCD, including, but not limited to, short-distance inter-device wireless communication systems (such as Bluetooth or NFC), cellular-network messaging (such as SMS) and Internet-based messaging (such as electronic mail services and Website message facilities); another means may be the display and acquisition of a two-dimensional pattern (i.e. a pattern that has variations independently along two orthogonal axes), whose configuration uniquely corresponds to the Site Message.

Further according to the present invention, every MCD assumed to be carried by a person using the system is operative to receive any Site Message from any nearby OSD and to send it to a Verification Server (VS - to be described below). Depending on system configuration, the address of the VS may be stored in the MCD or may be obtained from the OSD.

Further according to the present invention, there is provided a digital server, termed

Verification Server (VS), associated with data storage facility and operative to - - communicate with a plurality of MCDs,

- to receive Site Messages from any MCD, to decrypt and decode it and to accordingly verify the MCD's current location at the indicated site, and

- optionally to transmit to the same MCD and/or to the indicated OSD particular information, retrieved from the storage, that is appropriate for the verified location and time period.

Depending on particular configurations and embodiments of the system, communication between the VS and the MCDs is by means of one or more cellular networks or by the combined means of a cellular network and the Internet.

In some configurations of the invented system, the MCD is operative to transmit to the VS also information about its own identity or that of the person carrying it and the information retrieved by the VS and transmitted back is, further, appropriate for that person.

More generally, the invention is of a system for verifying the presence of a mobile

communication device (MCD) at a physical site, the system comprising an on-site computing device (OSD), disposed at the site, and a remote verification server (VS), the server being communicative with the on-site device and with the mobile device, wherein -

- the on-site computing device has associated therewith a unique identification code and a unique encryption key and is operative to measure elapsed time from a reference time, to generate, frequently or on demand, a site message that contains (a) a current value of the elapsed time, encrypted according to the encryption key, and (b) the identification code and to make the site message available to the MCD while, and only while, the MCD is present at the site;

- the mobile communication device, while present at the site, is operative to obtain the site message from the OSD and to send it to the VS; and

- the verification server is operative, upon receiving a site message from the MCD, to decrypt the elapsed time value contained therein and to check its validity.

In some configurations of the system, the on-site computing device includes a display device, generating a site message is frequent and making the site message available includes generating a two-dimensional code pattern that continuously and uniquely represents the latest generated site message; and

the mobile communication device includes optical image acquisition capability and obtaining the site message from the OSD includes decoding a two-dimensional code pattern appearing in an acquired image. In some configurations of the system, both the OSD and the MCD are mutually communicative over a short-range wireless system and obtaining the site message from the OSD includes receiving the message over the wireless system.

According to a feature of the invention, the OSD is additionally operative to make available, and the MCD is additionally operative to obtain, along with the site message, a Web address of the VS. According to a further feature, the Web address and the site message are jointly encoded in the format of a Uniform Resource Locator.

According to other features of the invention, each site message is unique and valid only for a predefined duration; checking of validity by the VS includes checking for uniqueness and whether the decrypted elapsed time value is within the predefined duration.

According to yet other features of the invention, the VS is further operative, following the checking of validity, to accordingly send a message to the OSD or to the MCD or to each of them; the MCD may be further operative to enable a person that operates it to identify himself while communicating with the VS and any of the messages sent by the VS is also according to the identity of that person.

Generally the system comprises a plurality of on-site computing devices, similar to the OSD specified above, disposed in a plurality of sites. Preferably the time reference is unique to each OSD. In some configurations the system may comprise one or more additional verification servers, similar to the VS specified above, and sending of the site message is directed to any predefined one of all the verification servers.

In another aspect, the invention is of a method for verifying the presence of a mobile communication device (MCD) at a physical site, comprising

(i) providing an on-site computing device (OSD), disposed at the site, and a remote verification server (VS), the server being communicative with the on-site device and with the mobile device;

(ii) associating with the OSD a unique identification code and a unique encryption key;

(iii) in the OSD - measuring elapsed time from a given reference time,

encrypting a current value of said elapsed time according to said key,

generating a site message that contains said identification code and the encrypted version of said current value and making the site message available to the MCD while, and only while, the MCD is present at the site;

(iv) causing the MCD to obtain said site message from the OSD and to send it to the VS; and

(v) In the verification server - receiving the site message from the MCD, decrypting the elapsed time value contained therein and checking its validity.

In some applications of the method, the on-site computing device includes a display device and the said making the site message available includes generating a two-dimensional code pattern that continuously and uniquely represents the latest generated site message; and the mobile communication device includes optical image acquisition capability and the said obtaining the site message from the OSD includes decoding a two-dimensional code pattern appearing in an acquired image.

In yet another aspect, the invention is of a method for transferring data, which vary with time or are time-dependent, from a first computing device to a second computing device, the first device having a display means and the second device having image acquisition capability, the method comprising

(i) in the first device, repeatedly generating a two-dimensional code pattern that continuously and uniquely represents the data and displaying said pattern;

(ii) in the second device, optically acquiring said displayed pattern, at any instant, to obtain a digital image thereof;

(iii) processing said image so as to extract the code pattern therein and decoding the pattern to obtain the data;

wherein said displayed pattern varies with time in correspondence with the variation of the data.

LIST OF DRAWINGS

Figure 1 is a schematic overall diagram of a system according to the present invention.

Figure 2 is a flow diagram illustrating the manner of encoding verification data according to an embodiment of the present invention. DESCRIPTION OF PREFERRED EMBODIMENTS

Turning to Figure 1, there is shown schematically an embodiment of a system according to the present invention for verifying the presence of a person at a particular site and at a particular time period and possibly sending to him information that is relevant to that site and that time period.

A digital server 50, to be termed Verifying Server (VS), is operative to be in two-way communication with a plurality of mobile communication devices 20 (MCD). The VS 50 may be any suitable computer or computing system and has associated with it one or more digital storage facility 55 (briefly: Storage); it may also be a facility within a multi-purpose host computer. The VS is preferably accessible through the WWW facility of the Internet, being addressable by a Uniform Resource Locator (URL); the URL may also include the name of a resource within the VS that serves to activate its function in the context of the invented system, as explained further below. There may be more than one VS in a system.

The communication path 40 between the VS and the MCDs may include any publicly accessible medium, such as (but not limited to) the Internet, a cellular network or a land-line network and may include, in addition, any local wireless communication means (e.g. WAP, wi-fi or Blue Tooth). Some configurations of the system may be limited to one or two of these media.

A mobile communication device 20 (MCD) may, in the present context, be any mobile device, such as, for example, a cellular telephone or a tablet computer, that has data processing and display capabilities and that is operative to run digital application programs and to communicate with a VS 50 over the path 40. Each MCD 20 is assumed to be associated with, and held and operated by, a corresponding person 25, whose presence at a site 30 is to be verified. Preferably the MCD has also optical image acquisition capability (i.e. a camera function) and/or a short-distance inter-device wireless communication capability, such as Bluetooth or NFC.

A site 30, in the present context, is characterized by the presence of a so-called On-Site Device (OSD) 10. Fig. 1 depicts one such site, but there is generally a plurality of such sites in a system. A site 30 may be in a geographically fixed position or its position may change from time to time or it may be moving (e.g. on a vehicle). It is noted that a site is uniquely associated with an OSD and defined, in the present context, in terms of proximity thereto (dictated by the means of communication between the OSD and the MCD, as explained below and typically amounting to a radius of up to a few meters); thus, for example, there may be several distinct sites and associated OSDs in a large store. At all times the current location of each site 30 is preferably known and stored at VS 50. Each OSD 10 is communicative with at least one Verifying Server 50 through communication path 40 - which preferably is the Internet.

An On-Site Device (OSD) 10 may be any device that includes a computing facility (e.g. a digital processor and storage) and a display screen 15 In some configurations of the system, the display screen is viewable by any person at the site (as explained below) and, with appropriate software, the OSD is capable of generating two-dimensional code patterns on the screen that represent corresponding messages or strings of characters (such as ASCII encoded characters). It is noted that such a display capability is sometimes used for purposes of identifying the device, or a process running therein, (by means of an imaging MCD) and therefore such a device is sometimes referred to as a dynamic visual identifier (DVI). An OSD may be, for example, an office computer (with attached screen), a portable computer, a tablet computer, a cellular telephone or a dedicated device.

Each OSD 10 has, stored therein, a unique fixed identification code, which is also associated with its site 30 and is therefore referred to as the site ID; it is also stored at the VS (e.g. at storage 55). In addition, each OSD maintains a variable code that represents the value of the current time period and is therefore referred to as the time ID. A current time period is the latest of a series of consecutive time periods of a given length (typically several seconds to one minute) and its value is the time at which it started, which is derived from a clock in the OSD. Since the OSD is connected to a network (such as a cellular network or the Internet), its clock may be synchronized with a timing server therein; otherwise its accuracy may be checked occasionally and any deviations may be compensated for in the ensuing process. Preferably, the value of the time ID is expressed as the number of seconds elapsed since a given reference time. The reference time may be fixed and universal, but more preferably it is unique for each OSD and secret. In the latter case it is stored at the VS, in association with its site ID, and serves as an element in the process of validation, as explained below. The reference time of any OSD is set by the VS and may be changed by it occasionally. It is noted that for the purpose of subsequent verification, the time ID serves as a password and since it changes periodically it is valid as such for the duration of a period only and expires thereafter. It is further noted that, since the period is relatively short, the probability that more than one MCD obtain the same time ID is relatively small, which renders the time ID as a unique password.

Associated with each OSD is a unique shared secret key for encrypting the time ID; it is stored at the VS, in association with its site ID, and serves in the process of decryption. In some configurations of the system, there is also stored in each OSD a Uniform Resource Locator (URL) of a Verifying Server (VS) - i.e. its Web address and the name of a relevant resource therein.

To be operative within the system, according to the invention, each OSD 10 is loaded with software that makes it operative to continuously maintain the variable time ID and repeatedly or on-demand (depending on the configuration) - to encrypt it according to the secret key, using an encryption algorithm;

package the encrypted time ID together with the site ID into a so-called Site Message and to send, or make available, the site message to any MCD at the site.

In preferred embodiments the OSD is further operative to format the site message as a string of ASCII-encoded characters, which are readily processable by many common application software packages in MCDs. This string is herein referred to as a Transmission String. In some configurations of the system the transmission string also includes the Web address of the VS (or any resource therein) and is preferably formatted as a URL.

There are several means available for transmitting the data (i.e. the site message or the transmission string) from the OSD to a nearby MCD, such as outlined below. Various MCDs may be operative to use variously one or more of these means and the OSD is preferably operative to use all of them.

A readily available and commonly used transmission means is a so-called two-dimensional bar-code (2D barcode), which is displayable on the screen of the OSD. It is a particular format of a two-dimensional binary pattern code, consisting of black and white elementary areas. The data to be transmitted (i.e. the site message itself or the transmission string) are encodable into a corresponding pattern configuration by readily available encoding software. By repeatedly displaying on its screen a pattern code that corresponds to a current site message, the OSD is thus operative to make the site message available to any suitably equipped MCD (as explained below)

Other means for transmitting the data from the OSD to any MCD may include, for example, the following:

(a) A short-range wireless data communication system, such as Bluetooth or Near- Field Communication (NFC) system, which is generally configured to automatically establish communication between the devices when in close proximity or (in the case of NFC) when in mutual contact;

(b) Communication over the Internet, using any of a variety of suitable Web services or applications that enable exchange of messages, such as a social network, or possibly one provided as part of the system;

(c) Communication over the Internet, using electronic mail;

(d) Communication through the cellular network, sending the transmission string, for example, as an SMS message.

In order to avail itself of the system disclosed herein, MCD 20, should be operative to -

- receive the data sent, or made available, by the OSD, through at least one of the means for which the OSD is operative;

- extract from the received data (e.g. the transmission string) the address (if included) of the verification server and the site message; and

- send the latter, over Communication Path 40, to the VS.

Software application programs are readily available to carry out the above-listed functions, but a dedicated application is also contemplated as an optional part of the disclosed system. To be able to obtain data made available by the OSD as a displayed pattern (e.g. 2D barcode), the MCD must have image acquisition capabilities, including a camera, and software operative to capture the image of the pattern and to decode it so as to as to reconstruct the transmission string. Such software is also readily available.

The VS address may, in some configurations, especially when the path thereto is via the cellular network, be stored in the MCD or be part of the application. However, generally and preferably, the path 40 is the Internet and preferably the VS address is provided from the OSD as part of the transmission string. More preferably, the transmission string is formatted as a URL; in this configuration of the system, the MCD need only be operative to apply the received string to a standard Web browser, which is operative to automatically send it on to the VS. Software application programs are readily available to carry this out automatically; some of them, moreover, combine this function with the function of receiving the

transmission string from the OSD, especially when using the optical (2D barcode) or any of the wireless means of transmission, thus making the entire process simple, with minimal intervention by the operator of the MCD. It is noted that this simplicity of operation is an important advantage of the disclosed system.

In some configurations of the disclosed system, the MCD may send additional data to the VS, along with the Site Message, such as data relating to the identity of the MCD 20 and/or of its owner 25 or data keyed into the MCD. Generally, however, once communication between the MCD and the VS has been established, both devices may be operative to exchange information between them.

The Verifying Server 500 (VS) has access to the current time, as well as to data stored in storage 550, which include Site IDs of the OSDs associated with the system and user information related to them. The VS also has programs loaded therein that make it operative to -

- accept data addressed to it over the communication path 40 by any of the MCDs 20 in the system;

- extract from any thus received data the Site Message and any additional data (such as the identity of the MCD or of its owner or keyed- in data);

- extract from the Site Message the Site ID and the time ID and decrypt the latter, using a decryption algorithm and the secret key relevant to that site;

- compare the decrypted time ID with the current time period and accordingly validate the Site Message, thus verifying the current presence of the MCD at the indicated site; and

- in case of positive verification, retrieve from storage 550 information suitable to the identified site, according to suitability rules, and send it to the MCD and/or to the OSD.

It is noted that when the site message is packaged as a URL, the reception of transmitted data and the extraction of its components are part of the common functionality of Web servers.

In some configurations, the VS is further operative to use the identity of the MCD or its owner and any other relevant information, extracted from the received data in applying suitability rules, so as to retrieve from storage and send to the user information that is further suitable for that user, such as personal information related to his current location.

Typical operation of a preferred embodiment of a particular configuration of the system according to the present invention will now be explained, by way of an exemplifying illustration. The description will be in terms of a particular site and a particular user, with his MCD, but it should be understood that it is equally true for any other user and any other site associated with the system.

The OSD at the site continuously displays on its screen a 2D barcode pattern, which changes periodically. The pattern is generated as follows, with reference to the flow chart of Figure 2: There is stored a time reference 2 that is unique to the OSD and there is a date & time register 6, which keeps the real time and is occasionally synchronized with an external reliable time base. A Time ID value is periodically calculated 4, by subtracting the time reference from the current real time; the time ID is typically the number of seconds elapsed from the time reference to the instant of calculation. The length of the period, over which a current time ID is valid and at the end of which a new value is calculated, is a parameter that may typically vary between one second and one minute and is logically related to the expected time proximity at which different MCDs may successively obtain site messages from the OSD; the goal is to assure that different MCDs obtain different site messages, thus eventually enabling unique verification of the presence of each.

It is noted that the time ID is a particular form of a so-called one time password and is convenient because it does not require periodic communication with the VS to renew the password; instead, the VS (for the purpose of validation) reconstructs the password, i.e. the proper time ID (for comparison with the received value) using its own time register (which is directly or indirectly synchronous with those of the MCDs). It is further noted that the unique time reference of each OSD (all of which are stored at the VS) serves the VS to validate the identity of the OSD from which a site message has been received.

Calculation 4 yields a current time value 8, which is preferably concatenated with a pseudorandom number in order to increase the security of the encryption. This then undergoes encryption 10, which is carried out on the basis of a stored key 12 that is specific to the OSD and is also stored at the VS. The result is converted to a string of ASCII-encoded characters - by using, in the present embodiment, a commonly known process of encoding to base64 14. The resulting string is concatenated 15 with the site ID 11, to form the site message; thus [Site Message] = [Site ID] [encrypted time ID]. The Site Message is further concatenated 15 with the stored VS address and formatted into a URL string 16, e.g. http://[VS address]/[site message]. The URL string 16 is ready for transmission to a MCD.

In the present example, transmission to a MCD is carried out by means of 2D barcode;

however, generally an OSD would transmit by whatever means the nearby MCD initiates. The URL string is converted 18 to a 2D barcode pattern, which is displayed on the OSD's display device 20; there is a one-to-one relation between the pattern and the URL. It is noted that the entire process, described above, is repeated successively at the beginning of each period and therefore the displayed pattern changes periodically. It is a particular feature of the present invention to display a two-dimensional code pattern that generally changes with any changes in the data that it represents.

Reference is now again made to Figure 1. A user 25, carrying a MCD 20 and present at site 30 may be seeking information, or wishing to complete a transaction, relevant to that site. He spots and selects a, OSD 10 at that site, on whose screen is displayed a 2D barcode pattern, aims his MCD thereto and acquires an image of its screen. It is noted that the displayed pattern uniquely corresponds to a URL, with the Web address of the verification server and, in the resource field, a recoded version of the site message, which consists of the Site ID and the time ID, the latter encrypted, as described above. On command by the user, one or more software applications in the MCD then -

- capture the acquired image and extract therefrom the pattern that was displayed on the OSD screen;

- convert the pattern into the corresponding URL string; and

- inserts the URL in the address field of a Web browser page.

Optionally the user enters additional data into the page (which may be preformatted for the purpose). The resulting Web page is then sent, over the Internet (which is the preferred means for Communication Path 40), to the Verifying Server 50.

The VS addressed by the URL, upon receiving the sent data -

- extracts from the site message portion thereof the Site ID and the encrypted time ID;

- retrieves from storage 55 the encryption key and the time reference that correspond to the site ID and accordingly decrypts the time ID and converts it to a real time value;

- compares the obtained time value with the current time period (as kept in the VS's own register) and accordingly validates the site message, thus verifying the current presence of the MCD and its user at the site; and

- in case of positive verification, retrieves from storage 55 information, if any, suitable for the identified site and sends it, together with a verification notice, over the Internet, to the relevant OSD and/or MCD. Upon reception of the latter information, the vendor or the OSD is able to proceed with the transaction or with any other suitable action, as the case may be, and the user is possibly notified of the verification by means of his MCD, where he can also read any sent information..

It is noted that the presence verification is needed because the site identification data is available to every MCD nearby and can easily be copied and used at a different site and time - which may produce irrelevant or incorrect or even wrong information to the user or grant him unwarranted rights. By making the site identifier unique and valid only during a predefined time interval and by being securely encrypted in a site-specific manner, the presence of the correct user at a particular site and during a particular time interval is assured.

Claims

1. A system for verifying the presence of a mobile communication device (MCD) at a physical site, the system comprising an on-site computing device (OSD), disposed at the site, and a remote verification server (VS), the server being communicative with the on-site device and with the mobile device, wherein -

- the on-site computing device has associated therewith a unique identification code and a unique encryption key and is operative - to measure elapsed time from a reference time,

to generate, frequently or on demand, a site message that contains (a) a current value of said elapsed time, encrypted according to said key, and (b) said identification code and to make the site message available to the MCD while, and only while, the MCD is present at the site;

2. The system as in claim 1, wherein - the on-site computing device includes a display device, the said generating a site message is frequent and the said making the site message available includes generating a two- dimensional code pattern that continuously and uniquely represents the latest generated site message; and

the mobile communication device includes optical image acquisition capability and the said obtaining the site message from the OSD includes decoding a two-dimensional code pattern appearing in an acquired image..

3. The system as in claim 1, wherein both the OSD and the MCD are mutually

communicative over a short-range wireless system and the said obtaining the site message from the OSD includes receiving the message over said wireless system.

4. The system as in any of claims 1-3, wherein the OSD is additionally operative to make available, and the MCD is additionally operative to obtain, along with the site message, a Web address of the VS.

5. The system as in claim 4, wherein said Web address and the site message are jointly encoded in the format of a Uniform Resource Locator.

6. The system as in any of claims 1-5, wherein each site message is unique and said checking of validity by the VS includes checking for uniqueness.

7. The system as in any of claims 1-6, wherein each site message is valid only for a predefined duration and said checking of validity by the VS includes checking whether the decrypted elapsed time value is within the predefined duration.

8. The system as in any of claims 1-7, wherein the verification server is further operative, following said checking of validity, to accordingly send a message to the OSD or to the MCD or to each of them.

9. The system as in claim 8, wherein the MCD may be further operative to enable a person that operates it to identify himself while communicating with the VS and any of said messages sent by the VS is also according to the identity of said person.

10. The system as in any of claims 1-9, additionally comprising a plurality of on-site computing devices, similar to said OSD, disposed in a plurality of sites.

11. The system as in claim 10, wherein said time reference is unique to each OSD.

12. The system as in any of claims 1-11, additionally comprising one or more additional verification servers, similar to said VS, wherein said sending of the site message to the VS is directed to any predefined one of all the verification servers.

13. A method for verifying the presence of a mobile communication device (MCD) at a physical site, comprising

(iii) in the OSD - measuring elapsed time from a given reference time,

encrypting a current value of said elapsed time according to said key, generating a site message that contains said identification code and the encrypted version of said current value and

making the site message available to the MCD while, and only while, the MCD is present at the site;

14. The method as in claim 13, wherein

the on-site computing device includes a display device and the said making the site message available includes generating a two-dimensional code pattern that continuously and uniquely represents the latest generated site message; and

the mobile communication device includes optical image acquisition capability and the said obtaining the site message from the OSD includes decoding a two-dimensional code pattern appearing in an acquired image.

15. The method as in any of claims 13-14, wherein said time reference is unique to each OSD.

16. A method for transferring data, which vary with time or are time-dependent, from a first computing device to a second computing device, the first device having a display means and the second device having image acquisition capability, the method comprising