Patent Description:
Tradable Card Games (TCG), also known as collectible card games (CCG), are games played with tradable and collectible trading cards. Such games enjoy an increasing popularity. For example, the game "Magic: the Gathering" (MTG) has a large number of active players. Other examples of trading card games include: Pokémon TCG, World Of Warcraft TCG, Hearthstone, among many others. Hybrids forms between computer games and card games are also known. For example, in the game "Kantai Collection", players collect cards as in a TCG, but to play the game, the cards are scanned into a game console, e.g., an arcade console. Another example of such a computer game using tradable cards is "Sengoku Taisen".

In a TCG players collect cards that represent game elements, such as, characters, abilities or the like, which can be used during game play. Typically, players might acquire a large number of playing cards by buying many small stacks of new cards, known as a foil or a pack; often without knowing which playing cards will be included in the foil. From the large number of playing cards, a player assembles a set of cards, known as a deck, with which they can play the game. Players whose deck includes better cards, enjoy some advantage during game play. For example, a pack might contain <NUM> more or less random cards, while a deck might contain <NUM> selected cards.

The manufacture and sale of the cards used in tradable card games has grown to a large business. It is estimated there were <NUM> million players in <NUM>, with an increase of <NUM>% in the last four years. Apart from the sale of new cards, there is an active secondary market in which players may directly acquire the cards they require for their decks.

Unfortunately, counterfeiting of playing cards is a significant problem in this business. Playing cards are getting more and more expensive, and the incentive to counterfeit continuous to grow. Counterfeits are very hard to distinguish from authentic cards. Counterfeits erode consumer trust. Without trust in the collectability of the game, cards return to their intrinsic value.

There is therefore a desire to devise a technical solution for the problem of counterfeiting in the field of playing cards.

Document <CIT> discloses an electronic gaming machine e.g. slot machine. The machine has a user input device, e.g. touch pad, accepting user input for conducting play of a game in which game outcomes are provided responsive to a wager. A processor, i.e. CPU, provides a mechanism for transmitting messages between the machine and the input device in communication with the machine. The processor transmits a message between a smart card interaction device and a host server via a messaging communication protocol interface, where the server is in communication with the machine via a server-based gaming network, e.g. Internet.

The present invention is directed to a playing card system arranged to authenticate a playing card for playing a card game according to claim <NUM>; a playing card arranged for playing a card game according to claim <NUM>; a playing card authentication server for verifying the authenticity of a playing card according to claim <NUM>; a playing card authentication method to authenticate an electronic playing card according to claim <NUM>; and a computer readable medium according to claim <NUM>. Subsidiary aspects of the invention are provided in the dependent claims.

The problem is addressed by a playing card system, a playing card, a playing card authentication device, a playing card authentication server, a playing card authentication method, a computer readable medium, as described herein.

The playing card is arranged for playing a card game. The playing card comprises an electronic memory, an antenna, and a processing circuit. The memory stores authentication data. The antenna is arranged for wireless communication. The processing circuit is arranged for.

The authenticity of the card is verified using an authentication device and an authentication server. For example, the authentication device may interact with the playing card locally and wirelessly. The resulting token may then be verified using the authentication server, e.g., using information available at the server, e.g., corresponding authentication data. Note that the token may be generated on the playing card, so that the authentication data does not need to be available outside the card, or at least not all of it. This makes counterfeiting the card harder, since a counterfeiter does not know what information to include in the counterfeited card.

The playing card, authentication device and authentication server are electronic devices. In particular playing card, and authentication device may be mobile electronic devices.

In an embodiment the authentication server is configured to generate a computer network address through which an information page is accessible over a computer network. The information page comprises information that indicates the result of the authentication of the playing card. For example, the computer network address may be made available to the playing card authentication device.

For example, the authentication server may generate a web page comprising information about the card. The information may comprise the authenticity of the card and/or its current owner. The information may also comprise the date and time when the authenticity of the card was last verified at the authentication server. The information may also comprise further information about the card, e.g., a picture, textual information and the like. The computer network address may be a URL. The computer network may be the Internet. The computer network address or the URL may be referred to as a proof link. The proof link may be valid for a limited duration. For example, in an embodiment, after the validity of the proof link expired the authentication server may be configured to show that the link expired instead of showing the authenticity information. This feature further reduces the possibility for fraud.

Another aspect of the invention concerns physical objects comprising an electronic memory, as the playing card described herein. Like playing card the physical objects may be verified using an online authentication server, via an authentication device. This can be applied, e.g., in objects such a brand shoes, perfume, and the like. An embodiment of the method may be implemented on a computer as a computer implemented method, or in dedicated hardware, or in a combination of both. Executable code for an embodiment of the method may be stored on a computer program product. Examples of computer program products include memory devices, optical storage devices, integrated circuits, servers, online software, etc. Preferably, the computer program product comprises non-transitory program code stored on a computer readable medium for performing an embodiment of the method when said program product is executed on a computer.

In an embodiment, the computer program comprises computer program code adapted to perform all or part of the steps of an embodiment of the method when the computer program is run on a computer. Preferably, the computer program is embodied on a computer readable medium.

Another aspect of the invention provides a method of making the computer program available for downloading. This aspect is used when the computer program is uploaded into, e.g., Apple's App Store, Google's Play Store, or Microsoft's Windows Store, and when the computer program is available for downloading from such a store.

Further details, aspects, and embodiments of the invention will be described, by way of example only, with reference to the drawings. In the Figures, elements which correspond to elements already described may have the same reference numerals. In the drawings,.

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail one or more specific embodiments, with the understanding that the present disclosure is to be considered as exemplary of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described.

Further, the invention is not limited to the embodiments, and the invention lies in each and every novel feature or combination of features described herein or recited in mutually different dependent claims.

As pointed out above, there is a desire for technical measures that will make counterfeiting harder. A possible solution to the counterfeiting problem is to embed an RFID tag in playing cards, e.g., a near field communication (NFC) tag. For example, the RFID tag may identify the card. An RFID reader, e.g., a mobile phone, an NFC reader, etc., may read-out the identifying information on the tag. If the identifying information on the tag corresponds to the identifying information that is visually printed on the card, it may be concluded that the card is authentic. This solution makes counterfeiting of cards harder since it requires the embedding and writing of an RFID tag in addition to an accurate visual reproduction of a card in order to counterfeit it. For example, a NFC tag may be used for the RFID tag. For example, an MTG playing card may have its unique identifier stored on an RFID chip embedded in the playing card. For example, if one reads out the unique identifier, say 5d8a7f95-ac4c-<NUM>-8bdd-55336b86b98c, one can look-up that this identifier corresponds to a card with a card type which has the so-called multiverseid <NUM> and name "Lord of the Pit". One could also store only the card type identifier, or multiverseid, but this prevents card-specific information to be added on a server, such as experience points or the owner of the card. The link between the unique physical card and its digital representation using the unique identifier is called a digital twin. If the card in question is found or identified as a "Lord of the Pit", one can conclude that it is likely authentic. Although this solution is an improvement over card without an embedded RFID chip, it was found that solution is not inadequate, since RFID tags can be copied too easily.

<FIG> schematically shows an example of an embodiment of a playing card system <NUM> that addresses this problem. System <NUM> comprises a playing card authentication device <NUM>, and an authentication server <NUM>. The system may also comprise one or more playing cards. <FIG> shows one playing card <NUM>, there may be more playing cards.

For example, in operation of system <NUM>, playing card authentication device <NUM> may interact wirelessly with playing card <NUM>. For example, a playing card authentication device <NUM> may receive a cryptographic token derived from authentication information stored on playing card <NUM>. Playing card authentication device <NUM> and playing card <NUM> are located near each other so that the two devices can communicate through a direct wireless connection. Playing card authentication device <NUM> can then authenticate playing card <NUM> with authentication server <NUM>. For example, server <NUM> may verify the cryptographic token. The result of the authentication may be displayed as a success or failure signal on authentication device <NUM>. As part of the authentication operation, playing card <NUM> may be modified; for example, a counter may be increased and/or the authentication data may be modified, e.g., overwritten.

Playing card <NUM> comprises an electronic memory <NUM>, an antenna <NUM> and a processing circuit <NUM>. For example, memory <NUM>, antenna <NUM> and circuit <NUM> may be implemented as an RFID tag, e.g., an NFC tag. Antenna <NUM> is arranged for wireless communication, e.g., RF communication, e.g., NFC communication. In an embodiment, the wireless communication may be of another type, e.g., Bluetooth, ZigBee, Wi-Fi, UHF, etc., but NFC is at this moment preferred. The playing card may receive commands over antenna <NUM> which may be executed by circuit <NUM>. Circuit <NUM> may be a simple circuit, configured only for the specific functions of an embodiment, or may be a general purpose circuit programmed therefore. NFC may be used for wireless communication between a chip in card <NUM> and device <NUM>.

Playing card <NUM> may be a paper card, a laminated card, a plastic card, etc., in which circuity is embedded.

The memory <NUM> is wirelessly readable, e.g., by playing card authentication device <NUM>. For example, playing card authentication device <NUM> may, e.g., send a read command to antenna <NUM>. In an embodiment, memory <NUM> is also writable, e.g., by sending a write command to antenna <NUM>. However, writing to memory <NUM> is optionally. For example, memory <NUM> may be read-only. For example, the contents of memory <NUM> may be set during manufacture of playing card <NUM>. For example, memory <NUM> may be a write-once memory. Un-writable memories have the advantage that a counterfeiter cannot change the memories content. However, as described below some embodiments make use of writable memories, to gain an advantage. Memory <NUM> comprises at least authentication data <NUM>, and preferably also a counter <NUM>. The authentication data <NUM> may be used in an authentication operation that proves the authenticity of the card. For example, authentication data <NUM> may be a random number, e.g., chosen at random at manufacture, or during a later operation, e.g., during an authentication operation. For example, a random number is a number that cannot be predicted. For example, authentication data <NUM> may comprise a cryptographic key, e.g., a symmetric key, e.g., a private key of a public/private key pair. The counter may be increased whenever the authentication data <NUM> is involved in an operation, e.g., whenever an authentication operation is performed and/or whenever the authentication data is renewed. The initial value of the counter may be a default number, e.g., zero, which may be the same for all playing cards, e.g., all playing cards of this type; the initial value may be a random value. Memory <NUM> may store a unique identifier, or additional information such as card type, e.g. its multiverseid.

The processing circuit may be configured to receive digital commands over the antenna from playing card authentication device <NUM>. For example, the command may be an authenticate command, that instructs the card to authenticate itself to device <NUM>. In response to receiving the command, the circuit creates an authentication token. Creating the token comprises reading the authentication data from memory <NUM> and the counter from the memory <NUM> and applying a cryptographic function thereto. There are several ways in which this can be done, some examples of which are described below. After the construction of the token, the authentication token is transmitted wirelessly to authentication device <NUM>, e.g., through the antenna <NUM>. After creation or after transmission, e.g., after complete or successful transmission, counter <NUM> in memory <NUM> is increased. For example, the counter may be increased directly after reading of the authentication data or after creation of the token. For example, the counter may be increased after receiving an acknowledgement of device <NUM> that a token has been successfully received.

Memory <NUM> may store additional information relevant to playing card <NUM>. For example, memory <NUM> may store a playing card identifier. The playing card identifier may be included in the authentication token, or may be transmitted along with the token. For example, the playing card identifier may be a unique number, e.g., a UUID. The playing card identifier may or may not be an input in computing the authentication token.

Processing circuit, and memory may be integrated in an IC, e.g., an NFC IC. The IC may be embedded in the playing card. The IC may be configured to perform cryptographic operations. The IC may be able to run general purpose computer instructions, e.g., applications, this is however not necessary. For example, the IC may be hardwired to execute only a limited set of operations. In an embodiment, the memory may be read wirelessly. However, in an embodiment, the memory cannot directly be read wireless, and can only be access through the processing circuit. This has a security advantage, if the contents of the memory cannot be obtained it cannot be copied either. For example, the circuit may be configured to read the memory, e.g., the authentication data, but to only transmit the authentication data after the cryptographic function has been applied to the authentication data, e.g., in the form of an authentication token.

Authentication device <NUM> may be configured to verify the authenticity of a playing card, in particular of playing card <NUM>. The playing card authentication device comprises an antenna <NUM> arranged for wireless communication with a playing card. For example, antenna <NUM> and antenna <NUM> may be arranged for the same type of wireless communication, e.g., the same type of RF communication, e.g., the same type of near field communication (NFC).

In addition to antenna <NUM>, authentication device <NUM> may also comprise a communication unit <NUM> arranged to communicate over a computer network to playing card authentication server <NUM>. For example, communication unit may be configured to communicate over the Internet. Communication unit <NUM> may also be wireless, e.g., configured for Wi-Fi, <NUM>, <NUM> or the like. The wireless communication type of communication unit <NUM> may be different from the communication type used by antenna <NUM> and <NUM>.

Authentication device <NUM> comprises a processing circuit <NUM> and a memory <NUM>. For example, memory <NUM> may store computer instructions executable by processing circuit <NUM>. For example, the processing circuit <NUM> may be configured to wirelessly send a digital authentication command over the antenna to playing card <NUM>. For example, the playing card <NUM> may be arranged to cooperate with authentication device <NUM> and to transmit at least an authentication token in response. For example, processing circuit <NUM> may be configured to receive from playing card <NUM> the authentication token in response to the digital authentication command. Authentication device <NUM> may be configured to send the authentication token to the authentication server through the communication unit, and receive from the authentication server information on the authenticity of the playing card. For example, authentication device <NUM> may receive from server <NUM> whether or not playing card <NUM> is authentic, e.g., genuine, or not. Device <NUM> may also receive from server <NUM> updated authentication data which is to be transferred to device <NUM>.

Authentication device <NUM> may comprise a display <NUM> configured to show information of the authentication operation. For example, device <NUM> may be configured to display information on the kind of playing card, e.g., received from playing card <NUM>, or from authentication server <NUM>. Display <NUM> may also be used to display the result of the authentication operation. Before sending on the token, authentication device <NUM> may add or modify information. For example, authentication device <NUM> may sign the token with a cryptographic key, e.g., a private key, to indicate to server <NUM> that authentication device <NUM> itself is an authentic device.

Authentication server <NUM> may be configured to verify the authenticity of a playing card, in particular playing card <NUM>. Playing card authentication server <NUM> may comprise a communication unit <NUM> arranged to communicate over a computer network with playing card authentication device <NUM>. For example, communication unit <NUM> may be configured to use the same computer network as authentication device <NUM>, e.g., the Internet.

Authentication server comprises a memory <NUM>. Memory <NUM> may be configured to store computer instructions for execution by a processing circuit <NUM>. However, memory <NUM> may also be configured to store authentication data <NUM> and a counter <NUM>. For example, authentication data <NUM> and a counter <NUM> may be retrieved from a playing card database <NUM>. Playing card database <NUM> may be part of server <NUM>, or may be external to server <NUM>. For example, database <NUM> may be stored on an external server in digital communication with server <NUM>, e.g., in the cloud.

For example, playing card database <NUM> may store authentication data <NUM> and a counter <NUM> indexed with a playing card identifier, e.g., the playing card identifier of playing card <NUM>.

In an embodiment, counter <NUM> is supposed to be equal to counter <NUM>. After successfully authentication of card <NUM>, counter <NUM> is increased, so that counter <NUM> and counter <NUM> remain the same. Only if there have been problems, or if playing card <NUM> is not authentic may counter <NUM> and counter <NUM> diverge from each other.

Increasing counter <NUM> at card <NUM> may be performed upon instruction of server <NUM>. In this case, one problem that may occur is that increasing of counter <NUM> fails for some reason, e.g., because the card is removed from a near field before the operation is complete. In that case, counter <NUM> may be larger than counter <NUM>. To avoid that counter <NUM> may become lower than counter <NUM> in this scenario, card <NUM> may be configured to increase counter <NUM> before computing the authentication token.

Accordingly, it may happen that the counter on the card and the counter on the server diverge. To counter this problem, a card may be accepted as authentic if counter <NUM> minus counter <NUM> is less than a threshold. For example, one may have the equation: counter <NUM> + #problems = counter <NUM>, so that one may accept if the number of problems #problems = counter <NUM> - counter <NUM> is less than a threshold, e.g., less than <NUM>, less than <NUM>, etc. The threshold may be determined empirically as a tradeoff between security and user friendliness.

On the other hand, for example, in an embodiment the counter may be increased whenever the authentication data <NUM> is involved in an operation, e.g., whenever an authentication operation is performed and/or whenever the authentication data is renewed; regardless of the fact that a resulting token is verified on the authentication device or the authentication server. This procedure has the advantage that it reduces communication between playing card and authentication device; for example, it is not needed to give an additional command to the playing card to increase its counter, e.g., after waiting for an acknowledgement of the server. Reducing communication also reduces that chance of corruption. It may still happen though that the counter on the card and the counter on the server diverge; for example, if for some reason the authentication device fails to forward the token, then the counter may be increased at the playing card but not at the server. In this situation the counter on the card may be higher than the counter on the server. To counter this problem, a card may be accepted as authentic if counter <NUM> is higher than counter <NUM>, e.g., if counter <NUM> minus counter <NUM> is less than a further threshold. Both options may be supported at the same time. The two thresholds need not be equal. If a token is accepted, even though the counters differ, then the counter on the server may be adjusted so that it is equal to the counter on the card.

In an embodiment, authentication data <NUM> and authentication data <NUM> are equal, e.g., equal numbers, equal cryptographic keys, etc. In an embodiment, authentication data <NUM> and authentication data <NUM> are corresponding members of a cryptographic key pair. For example, authentication data <NUM> may be a signing key and authentication data <NUM> may be the corresponding verification key. Signing key and verification key may form a cryptographic asymmetric key pair, e.g., an RSA key pair, an ECDSA key pair, etc..

Authentication server <NUM>, e.g., processor circuit <NUM>, may be configured to receive from playing card authentication device <NUM> an authentication token. The authentication token may be created by playing card <NUM> from authentication data <NUM> and optionally counter <NUM>, etc. The authentication token is verified using authentication data <NUM> and counter <NUM>. If the verification is successful, then a success signal may be sent to authentication device <NUM>. The success signal may indicate the authenticity of playing card <NUM> to playing card authentication device <NUM>. After successful authentication of playing card, the counter for that card, e.g., counter <NUM> and optionally also in the database is increased. By not increasing the counter in case of a failed authentication it is avoided that an attacker can distort counters. In an embodiment, the counter can be recovered from an authentication token, although this is not necessary.

To further improve security, the authentication device <NUM> and authentication server <NUM> may authenticate each other. For example, in an embodiment there may be many authentication devices <NUM> in the system. For example, authentication devices <NUM> may be implemented as a smartphone on which an appropriate app has been installed. There is thus a risk that an attacker may use fake authentication device. This risk can be reduced by authentication of the authentication device <NUM> to the server. For example, in an embodiment, playing card authentication device <NUM> may be configured to authenticate playing card authentication server <NUM>, and/or playing card authentication server <NUM> may be configured to authenticate playing card authentication device <NUM>. For example, device <NUM> and server <NUM> may be configured to perform an SSL handshake.

Below a number of examples of authentication tokens, their creation and authentication are given.

In an embodiment, the authentication data <NUM> and <NUM> are cryptographic keys. For example, authentication data <NUM> stored in the playing card may be a private key (Priv) of a public/private key pair, and the authentication data <NUM> stored in the playing card authentication server may be the public key (Pub) of the public/private key pair. For example, authentication data <NUM> stored in the playing card may be a symmetric key (K), and the authentication data <NUM> stored in the playing card authentication server may be the same key (K).

The authentication token may be computed by playing card <NUM>, e.g., circuit <NUM>, by using its key in a keyed cryptographic operation. For example, the keyed cryptographic operation may be a signature operation, an encryption operation, or a keyed hash operation. For example, the token may be computed by signing the counter. For example, the token may be computed by signing a challenge value received by playing card <NUM> from device <NUM>, e.g., together with an authentication command. The challenge value may be a nonce, e.g., a random number. Signing may be done with a private key and a symmetric key; in the latter case, the operation is sometimes referred to as computing a message authentication code.

Authentication server <NUM> may verify that the token was created by applying a keyed cryptographic function to a counter and/or a challenge by recreating the token from authentication data <NUM>, e.g., if authentication data <NUM> and authentication data <NUM> are equal. For example, server <NUM> may apply the same keyed cryptographic function, e.g., a signature, encryption or keyed hash operation, to counter <NUM> and/or the challenge, and verify that server <NUM> computed the same token as received from playing card <NUM> via device <NUM>. Alternatively, if authentication data <NUM> and authentication data <NUM> are part of a cryptographic key pair, the server may perform the corresponding keyed function, using authentication data <NUM> as key. For example, perform a signature verification to verify if the token is a valid signature of counter <NUM>, or a decryption operation using authentication data <NUM> as key and verify that the outcome is counter <NUM>.

In an embodiment, device <NUM> first contacts server <NUM> to request a challenge. Server <NUM> then generates a challenge, e.g., a random number, and sends it to device <NUM>. Device <NUM> then sends the authentication command together with the challenge. Playing card <NUM> then applies the cryptographic function to the challenge, or to the challenge and counter <NUM>. Server <NUM> can then verify that the token corresponds to counter <NUM> as well as to the challenge.

Verifying the counter <NUM> is easiest if it were required that counter <NUM> and counter <NUM> are equal. In practice, a difference can be accommodated by verifying the token for counter <NUM> minus a number of small decrements, e.g., minus <NUM>, minus <NUM>, etc., up to the threshold. In addition or instead, increments may be used as required. This allows for the fact that an authentication may succeed at device <NUM> and server <NUM> but incrementing the counter at the card may fail, etc., or if increasing the counter at card succeeds but authentication fails at device <NUM> or server <NUM>. This approach may cause that the verification is performed multiple times. In an embodiment, the cryptographic function is a keyed bijective function; for example, an encryption or a signature with message recovery. This has the advantage that counter <NUM> can be recovered from the token, by applying the keyed inverse function. In this case, the counter <NUM> and counter <NUM> can be explicitly compared. This gives more flexibility in allowing authentications to proceed even if counter <NUM> and counter <NUM> are not exactly equal. Moreover, no multiple verifications are needed for different values of the counter to cover the eventuality of a difference between the two counters.

In an embodiment, a token is computed, e.g., as above, and verified by server <NUM>, in addition server <NUM> generates and sends new authentication data <NUM> and updates authentication data <NUM>. Device <NUM> receives the new authentication data and sends it to playing card <NUM> for writing in memory <NUM>. For example, a new symmetric key or new private key may be written in memory <NUM>. The new authentication data is also updated in server <NUM>, e.g., authentication data <NUM> and/or database <NUM>. This has the advantage that an illegal copy of playing card <NUM>, will have the old authentication data. For example, anytime a card is authenticated, its authentication data may be renewed, with the effect that all previous copies of the playing card become invalid. If one tries to authenticate an illegal copy, then its authentication data may not correspond to the authentication data stored in server <NUM>, and thus the authentication will fail.

In an embodiment, one could use a random string for the authentication data, without applying a cryptographic function, so that the token would equal the authentication data. If the authentication data is always updated then this would be a particular low-cost solution for authenticating playing cards. To verify the token, server <NUM> compares it to the stored authentication data.

An advantage of updating the authentication data is that duplicates of the card are automatically invalided. If a user makes an unauthorized copy of a card, then the first card that is verified with server <NUM> is the valid card, at least in so far as the server can determine. This is an incentive not to allow one's card to be copied, since if the copy is verified first, the original is automatically invalided.

For example, the playing card authentication server may be arranged to generate new authentication data, and if the verification succeeded, send the new authentication data to the playing card authentication device. The new authentication data may be a new key or a new random string. The playing card authentication device may be arranged to receive the new authentication data over the communication unit, and send the new authentication data to the playing card over the antenna. The playing card may be arranged to receive the new authentication data over the antenna and write the new authentication data to the memory.

In an embodiment, memory <NUM> may store a key. Processing circuit <NUM> may be configured to encrypt the counter using the key. The token may comprise the encrypted counter. Processing circuit <NUM> may receive a challenge from authentication device <NUM>. The challenge may also be encrypted. Instead of encryption a signature may be computed and included in the token. The signature may be an asymmetric signature or symmetric signature, e.g., a MAC, e.g., a keyed hash, etc. The key may be a private key.

In an embodiment, memory <NUM> stores the private key and a corresponding public key. The public key may be retrieved from the chip by device <NUM>. The counter may also be retrieved. The token may comprise, or be, a signature over the counter and/or a challenge. The authentication device <NUM> may use the public key to verify the signature. For example, the signature may be verified over the counter and/or the challenge. The public key may be protected using conventional means, e.g., with a signed certificate, such as a X. <NUM> certificate. Interestingly, this allows the token to be verified locally, e.g., using the key read from the playing card, and non-locally, at server <NUM> using a public key stored at server <NUM>. In an embodiment, the authentication data on playing card <NUM> is updated only if the token is verified through server <NUM> but not when it is verified locally. Note that updating authentication data is optional.

In an embodiment, before authenticating playing card <NUM>, authentication device <NUM> requests a challenge from server <NUM>. Server <NUM> generates the challenge and sends it to authentication device <NUM>. Authentication device <NUM> then requests a token from playing card <NUM>. Playing card <NUM> may process the challenge, e.g., with the counter, with the key, e.g., encrypt or sign it. The token may also comprise an identifier of playing card <NUM>. Authentication device <NUM> may then forward the token to server <NUM> for verification.

The system may be used to store one or more game parameters. For example, a game parameter may be stored at card <NUM> and/or at server <NUM>. When the game parameter is needed, e.g., in game play it may be retrieved from card <NUM> and/or at server <NUM>, e.g., by an authentication device, e.g., a mobile phone.

For example, memory <NUM> may comprise a game parameter which can enhance game play in several ways. For example, the game parameter may be modified when the playing card's authenticity is verified. For example, if an authentication token was sent by the playing card which correctly verifies, then a modified game parameter may be provided. For example, the modified game parameter may be provided to the playing card and stored thereon. For example, the modified game parameter may be shown on a display of the authentication device. The game parameter may be stored at server <NUM> instead or in addition.

For example, the game parameter may represent so-called experience points. For example, a card may gain experience points, which may be stored in a database, e.g., at server <NUM> and/or card <NUM>. Experience points may be gained by playing with the card on a tournament. Cards may become better over time by gaining experience points. This would incentivize players to attend tournaments by leveling-up cards. Furthermore, the monetary value of cards comes from playing the game, not from using them as a proxy stock-market.

<FIG> schematically shows an example of an embodiment of a playing card system <NUM>. <FIG> shows a playing card <NUM>. Playing card <NUM> has printed information <NUM> visible on it. The printed information <NUM> may comprise a picture <NUM> and text <NUM>. For example, the picture may show a game character and the text may show game parameters, e.g., capabilities, or the like.

Playing card <NUM> may comprise a chip <NUM>, and an antenna <NUM>. Chip and antenna may be configured as described herein. For example, antenna <NUM> may be arranged for wireless communication, e.g., with an authentication device. Chip <NUM> may be configured to.

<FIG> further shows a mobile phone <NUM>. Mobile phone <NUM> may be configured as an authentication device. Mobile phone <NUM> may comprise a communication unit arranged to communicate over a computer network to a playing card authentication server, and an antenna arranged for wireless communication with a playing card, such as playing card <NUM>.

Mobile phone <NUM>, e.g., an app installed thereon, may be configured to communicate with chip <NUM> and receive information. The information may comprise an ID that identifies card <NUM>. Mobile phone <NUM> may obtain information regarding this playing card and/or this type of playing card. For example, phone <NUM> may obtain the information from chip <NUM> or from a server, e.g., such as server <NUM>. For example, the playing card authentication server may be arranged to send information regarding the playing card for display on the playing card authentication device. For example, the information may be requested from server <NUM> using the ID. Mobile phone <NUM> may be configured to display the information. For example, in this case, phone <NUM> displays a picture, e.g., picture <NUM>, text, e.g., text <NUM>, additional text <NUM>. For example, additional text <NUM> may comprise additional game parameters. Phone <NUM> may be configured to.

When a playing card, such as card <NUM> or <NUM>, is first used it may be claimed by the user. For example, the authentication device, e.g., <NUM> or <NUM>, may comprise a user identifier which identifies a user of a further service of the playing card authentication server. The playing card authentication device may be configured to send the user identifier with the authentication token. The playing card authentication server is arranged to associate the user identifier with the playing card identifier in the memory of the playing card authentication server, the playing card authentication server being arranged to provide access to the playing card in the further service. For example, after manufacture of card <NUM> or <NUM>, its ID may be registered with the server. The card may initially be registered as unclaimed. When the token for the card is first received, and verified, a user ID that is received with the token may be stored by the server as the owner, or claimant, of the playing card. For example, a playing card may be scanned by a consumer after opening a pack in order to claim ownership, e.g., using his smart phone. The initial seller, such as the manufacturer or a retailer, might be the first owner of the card. In this case the seller needs to transfer ownership to the buyer of the card. This can be linked to a cash-register or an online e-commerce store. The store may be the current owner; upon payment, the owner would be transferred, or the owner-locked status would be set free, so someone, e.g., the purchaser, could claim ownership.

When a user acquires the card from a previous owner, he can send a token with the new user ID to register the new owner or claimant of the card. This allows users to manage their card collection online, e.g., through a website maintained by server <NUM>. It also allows the system to trace theft, mark a card as missing or set a transfer-lock on a card. For example, a transfer-lock may be implemented by storing, e.g., at server <NUM> a blacklist of card-ids that are not be transferred. For example, if a card is stolen, it may be reported as such through the online collection, e.g., the website. If a claim for the card is received a signal may be generated so that an appropriate follow-up action can be taken, e.g., require the new owner to legally identify himself. Depending on the configuration, there can be different requirements to transfer digital ownership of the card. One example is that physical access to a card is leading to transfer ownership, so that an authentication token can be used to validate the operation. Another example is that only digital ownership is required to transfer ownership. The last example is that both physical and digital ownership are required to transfer ownership.

Interestingly, this allows a user to link his physical card collection to an online card collection, also referred to as "digital twins". For example, scanning an NFC-card and transferring ownership adds it to one's online collection. This may allow one to play a game both online and offline using the playing card in one's possession. For example, server <NUM> may be arranged for online game play between two or more players using their online card collections. Offline the same or different users may use their physical cards to play the same or a different game. Interestingly, online game play may allow game parameters to be altered. When a playing card is verified, an altered game parameter may be downloaded on to the card. An authentication device, e.g., a mobile phone, may be used to write and/or read out the game parameter. This allows offline play, using an altered game parameter that was altered through online play. For example, a card may level up online, which may benefit a user offline when using the physical, e.g., paper, card.

For example, the playing card authentication server may maintain a collection of cards for multiple users, e.g., players, e.g., in a database storing cards that have been authenticated for a user. The server may offer additional services in various forms, for example, the server may provide a digital game play interface configured to receive a game play instruction referencing a card of the user. For example, the instruction may be a game play move, e.g., received from the user, or from some other user. The instruction may refer to a card of said user for some game-related purpose. Before allowing the instruction to complete, e.g., to perform some game-related objective, the playing card authentication server may verify that the referenced card has been authenticated for the user, e.g., by referring to the database. The server may operate this interface for its own purpose, e.g., if the server is also configured as a game server; however, the server may also or instead perform this service for third-party game servers. This feature makes it possible that online game mirrors the games that can be played in real life, e.g., with the same cards.

A potential problem with updating playing cards wirelessly, especially if the playing card does not have its own power source is corruption of the playing card date. This problem may be addressed by a card memory that comprises at least two areas for storing authentication data. The processor of the card being arranged to write the authentication data to the memory to a different area than the area storing the authentication data used to generate the authentication token. This ensures that authentication data that was used to validly create a token, and which is thus non-corrupted, remains valid and on the card. A next time a token is needed the updated data is used, so that the old authentication data is overwritten. For example, the areas may include the counters, so that initially the highest counter is used to generate the token, only if the data is corrupted or the token turns out to be invalid a token is created using the older data.

Another potential problem is that someone may try to claim a card without buying the card, e.g., while it is in the store, e.g., to claim it as the first owner. One might do this to add the card to an online collection without having to buy the card, e.g., to aid online game play, or perhaps to be a nuisance. There are several ways in which this problem may be addressed.

For example, the playing card may be wrapped in a foil, e.g., as part of a pack. The foil may be a metallic foil or may be lined with a metallic material to attenuate the wireless signal to and from the antenna of the playing card.

For example, a playing card pack may comprise, in addition to one or more playing cards a further card, the further card comprising an antenna arranged for wireless communication and a processing circuit arranged to distort the wireless signal of the one or more playing cards.

For example, a playing card may have its owner set to the retailer which is selling the card. Upon purchasing the retailer needs to un-set the card's owner, so that its buyer can claim the card, because it is not protected by any ownership, or the retailer needs to digitally transfer the cards ownership to its buyer. The buyer would communicate its player id to the retailer, for example by typing in a code, scanning a QR code, wirelessly transferring using <NUM>, WiFi or NFC. The code is then used to send a request to server <NUM>, which will update the card's owner.

Alternatively, a unique code, printed on the inside of the pack, or printed on a card included in the pack can be used to set the cards owner.

<FIG> schematically shows an example of an embodiment of a blockchain <NUM>. Shown are two blocks of the blockchain: block <NUM> and block <NUM>. The block comprises one or more transactions. Shown are transactions <NUM>, <NUM>, <NUM> and <NUM> in blocks <NUM> and <NUM> respectively. The blocks also comprise a consensus proof <NUM> and <NUM> respectively. The consensus proof is computed by a blockchain device, and may be, e.g., a proof of work, or a proof of stake, or the like. The transactions may indicate the claiming and/or transfer of a playing card. A transaction may indicate an authentication of a playing card.

<FIG> schematically shows an example of an embodiment of a blockchain network <NUM>. The blockchain network <NUM> comprises blockchain devices, shown are blockchain device <NUM>, <NUM> and <NUM>. For example, blockchain network <NUM> may be a peer to peer network, in which blocks of the blockchain, transactions, etc., are communicated. For example, an authentication device, e.g., device <NUM>, <NUM>, etc., or the server, may generate a blockchain transaction comprising the playing card identifier, and transmit the blockchain transaction to a blockchain network so that the transaction is processed by a blockchain management device for including in a block on the blockchain. The transaction may comprise the authentication token. A blockchain device is sometimes referred to as a miner.

In an embodiment, a card's public key may be stored in the blockchain, while the private key is uploaded to the chip. This may be done when the card is manufactured, or when the card is first claimed, etc. The blockchain may take the place of database <NUM>.

Saving cards or card transactions on the block chain prevents server side hacks. For example, the transaction lineage may be checked for a transaction. Furthermore, transferring a card twice becomes much harder, since it can be verified on the blockchain who is the owner of a card. The cost of hosting the blockchain devices could eventually be covered by players. For example, a blockchain miner may be rewarded with points that can be exchanged for exclusive mining foils.

In an embodiment of a card system or method, one or more of the following may be performed:.

Typically, the playing cards, authentication devices and servers each comprise a microprocessor which executes appropriate software stored at the device; for example, that software may have been downloaded and/or stored in a corresponding memory, e.g., a volatile memory such as RAM or a non-volatile memory such as Flash. Alternatively, the devices, especially the playing cards, may, in whole or in part, be implemented as a so-called application-specific integrated circuit (ASIC), e.g., an integrated circuit (IC) customized for their particular use. For example, the circuits may be implemented in CMOS, e.g., using a hardware description language such as Verilog, VHDL, etc..

In an embodiment, the playing card, authentication device and/or server may comprise one or more processing circuits to implement their functionality. The circuits may be a processor circuit and storage circuit, the processor circuit executing instructions represented electronically in the storage circuits.

A processor circuit may be implemented in a distributed fashion, e.g., as multiple sub-processor circuits. A storage may be distributed over multiple distributed sub-storages. Part or all of the memory may be an electronic memory, magnetic memory, etc. For example, the storage may have volatile and a non-volatile part. Part of the storage may be read-only. The circuits may also be, FPGA, ASIC or the like.

<FIG> schematically shows an example of an embodiment of a playing card authentication method <NUM>. Method <NUM> comprises.

Many different ways of executing the method are possible, as will be apparent to a person skilled in the art. For example, the order of the steps can be performed in the shown order, but the order of the steps can be varied or some steps may be executed in parallel. Moreover, in between steps other method steps may be inserted. The inserted steps may represent refinements of the method such as described herein, or may be unrelated to the method.

Embodiments of the method may be executed using software, which comprises instructions for causing a processor system to perform method <NUM>. Software may only include those steps taken by a particular sub-entity of the system. The software may be stored in a suitable storage medium, such as a hard disk, a floppy, a memory, an optical disc, etc. The software may be sent as a signal along a wire, or wireless, or using a data network, e.g., the Internet. The software may be made available for download and/or for remote usage on a server. Embodiments of the method may be executed using a bitstream arranged to configure programmable logic, e.g., a field-programmable gate array (FPGA), to perform the method.

It will be appreciated that the invention also extends to computer programs, particularly computer programs on or in a carrier, adapted for putting the invention into practice. The program may be in the form of source code, object code, a code intermediate source, and object code such as partially compiled form, or in any other form suitable for use in the implementation of an embodiment of the method. An embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the processing steps of at least one of the methods set forth. These instructions may be subdivided into subroutines and/or be stored in one or more files that may be linked statically or dynamically. Another embodiment relating to a computer program product comprises computer executable instructions corresponding to each of the means of at least one of the systems and/or products set forth.

<FIG> shows a computer readable medium <NUM> having a writable part <NUM> comprising a computer program <NUM>, the computer program <NUM> comprising instructions for implementing a playing card, authentication device and/or server on a processor system, according to an embodiment. The computer program <NUM> may be embodied on the computer readable medium <NUM> as physical marks or by means of magnetization of the computer readable medium <NUM>. However, any other suitable embodiment is conceivable as well. Furthermore, it will be appreciated that, although the computer readable medium <NUM> is shown here as an optical disc, the computer readable medium <NUM> may be any suitable computer readable medium, such as a hard disk, solid state memory, flash memory, etc., and may be non-recordable or recordable. The computer program <NUM> comprises instructions for causing a processor system to perform as a playing card, authentication device and/or server.

<FIG> shows in a schematic representation of a processor system <NUM> according to an embodiment of a playing card, authentication device and/or server. The processor system comprises one or more integrated circuits <NUM>. The architecture of the one or more integrated circuits <NUM> is schematically shown in <FIG>. Circuit <NUM> comprises a processing unit <NUM>, e.g., a CPU, for running computer program components to execute a method according to an embodiment and/or implement its modules or units. Circuit <NUM> comprises a memory <NUM> for storing programming code, data, etc. Part of memory <NUM> may be read-only. Circuit <NUM> may comprise a communication element <NUM>, e.g., an antenna, connectors or both, and the like. Circuit <NUM> may comprise a dedicated integrated circuit <NUM> for performing part or all of the processing defined in the method. Processor <NUM>, memory <NUM>, dedicated IC <NUM> and communication element <NUM> may be connected to each other via an interconnect <NUM>, say a bus. The processor system <NUM> may be arranged for contact and/or contact-less communication, using an antenna and/or connectors, respectively.

For example, in an embodiment, processor system <NUM>, e.g., the playing card, authentication device or authentication server may comprise a processor circuit and a memory circuit, the processor being arranged to execute software stored in the memory circuit. For example, the processor circuit may be an Intel Core i7 processor, ARM Cortex-R8, etc. In an embodiment, the processor circuit may be ARM Cortex M0. The memory circuit may be an ROM circuit, or a non-volatile memory, e.g., a flash memory. The memory circuit may be a volatile memory, e.g., an SRAM memory. In the latter case, the device may comprise a non-volatile software interface, e.g., a hard drive, a network interface, etc., arranged for providing the software.

<FIG> schematically shows an example of an embodiment of a playing card system <NUM>. <FIG> further visualizes claiming of an item, e.g., claiming ownership of the item.

System <NUM> comprises multiple playing cards; show is a playing card <NUM>. Playing card <NUM> may have various information printed thereon; shown is a card name 'card name <NUM>', and a picture. Playing card <NUM> comprises an electronic tag <NUM>. Tag <NUM> may store a playing card identifier, e.g., a number or the like. In an alternative embodiment, a computer readable identifier may be used, e.g., a QR code or the like. However, a QR code can simply be re-used so the latter is not preferred.

System <NUM> comprises a mobile scanning device <NUM>, e.g., a playing card authentication device. System <NUM> comprises an authentication platform <NUM>, e.g., a playing card authentication server. Mobile scanning device <NUM> is configured to read tag <NUM> and to communicate with authentication platform <NUM>. For example, authentication platform <NUM> may be configured to store information regarding the playing cards, e.g., playing card <NUM>. For example, authentication platform <NUM> may store item and identifier records. Authentication platform <NUM> may also store ownership information, e.g., an identifier of a user currently owning, e.g., most recently claimed, a particular playing card.

Shown in <FIG> is that mobile scanning device <NUM> and authentication platform <NUM> are configured for two protocols. A protocol to verify the authenticity of playing card <NUM>, and a protocol to claim ownership of playing card <NUM>.

<FIG> schematically shows an example of an embodiment of playing card system <NUM> in further detail in particular an example is shown of an embodiment of the protocol to verify the authenticity of playing card <NUM>. In response to a request from mobile scanning device <NUM> to verify the authenticity of playing card <NUM>, authentication platform <NUM> may generate a web-page which may be downloaded from authentication platform <NUM> by requesting a particular computer network address, e.g., a web-address, e.g., a URL. For example, in response to the request a proof URL may be generated. When visiting the URL, e.g. using a web-browser, the status of the card may be obtained.

Three possible response are shown in <FIG>. For example, according to web page <NUM>, the page contains the information that the card is authentic, e.g., that it is accounted for in the database of server <NUM>. Additional information may be when the card was validated.

Optionally, a proof link, such as the URL to web page <NUM> may be valid for a limited amount of time. Although, page <NUM> shows when the authenticity was last checked, this point may be missed by some consumers, and thus open a window for fraudulent transactions. A proof link according to this option is only valid for a limited amount of time. For example, web page <NUM> shows that the proof link expired. For example, according to web page <NUM>, the link may be invalid. For example, this page may be shown when the card could not be authenticated.

Accordingly, in this embodiment proof links may be generated, e.g., generation of a, possibly temporary, link, e.g. a URL, based on a scan of the playing card, with which authenticity but also physical access can be proven.

For example, in an embodiment, a user may scan his card with his mobile phone and receive a proof link in return. The proof link, e.g., a URL, may then be forwarded to some else, e.g., through a chat-app, marketplace, or e-mail or the like. For example, one could include the link when referring to the card online such as on a webpage; for example, the link may be included when the card is put up for sale on eBay or the like.

The other user may then verify the information, e.g., the authenticity of the card himself. For example, this may be used during negotiating a sale, or during game play or the like.

In an embodiment, the system is configured for a method to remotely proof the physical possession of a physical item such as a playing card. For example, scan a card and obtain a unique code from the authentication server. The code may be verified on the server. The unique code may comprise a computer network address, e.g., a URL, although this is not necessary. The unique code or URL may be sent to another party, e.g., a counterparty, another device, or the online marketplace. This token can be checked to prove whether and optionally when someone physically carried the product.

The marketplace is based on ownership registration of authenticated physical items such as playing cards. The marketplace may be implemented as a server or a cloud instance, etc., as an entity to and from one may send messages over a computer network. For example, the marketplace may comprise a computer. For example, the marketplace may comprise a web server. The marketplace may be integrated, e.g. comprised in, the authentication server.

In an embodiment, an online system is provided in which people register items they possess, and which may be verified using an authentication method. In the marketplace, owners may be regarded as potential sellers, as they have items which they might sell if the price or circumstances are right. For example, each time an owner scans or verifies the item, a field may be updated with the last time someone has interacted with it, and at which time the current owner has interacted with it.

Buyers looking to buy a certain type of product can query the server which holds all registered items. The buyer can place a price range and distance in the marketplace. The marketplace will then find potential sellers. The results from the query can be scored based on one or more of the following:.

The marketplace may add potential sellers to a list. To this list, new potential sellers may be added periodically for as long as the query is active. The buyer can manually indicate interest in a specific seller from those presented in the potential sellers list. The seller may then get a notification, e.g., push notification, email, etc., from the marketplace that someone is interested in buying an item they own. If the seller states he/she is also interested in selling, the buyer and seller can either:.

The marketplace may be configured to automatically find in parallel the highest scored potential sellers and notify interest to them. There can be a maximum number of simultaneous outstanding offers, e.g., configured for parallelism. The list of outstanding offers may periodically be checked for expired offers. If the maximum parallelism is not yet reached, the marketplace will add the next highest scoring offer to the current list.

Upon accepting a trade, the system may update the owner field of the item. From that moment on, the buyer seen as the registered owner of the item.

The marketplace may be configured with a rrecommender system for digital twins, collectibles, and the like. For example, the market place may be configured with a computer algorithm that analyses user-registered digital twins from owners of physical items from a database or subset of digital twins and owners, to detect latent or non-latent class membership of the object in order to recommend other objects, such as playing cards, that must be acquired in order to complete a manifest set of objects, such as a deck list or a game's expansion set, or a latent class, such as synergistic cards that are frequently associated with each other. An example of a latent class would be "Brainstorm" and "Fetchlands", although they are not directly related to each other, owners of "Fetchlands" would benefit from acquiring "Brainstorm" which is a well-known synergy in the card game Magic: the Gathering. The recommender system quantifies other non-obvious synergies. The detected item-associations are mapped to the related items in a database and are recommended to the user if he/she already owns part of the set. The greater the ownership share of the set, the higher the card is ranked in order of recommendations.

<FIG> schematically shows an example of a data model of an embodiment of a marketplace application. <FIG> schematically shows an example of a process diagram of an embodiment of the marketplace application. Interestingly, because items have an owner, the marketplace application has information that indicates who owns a particular card. The marketplace allows a prospective buyer of a card to ask owners of if they want to sell it.

For example, scoring may be done based on the information indicated in <FIG>, but also on location, e.g., GPS location, e.g., distance, and a user rating as a buyer and/or seller. The list of items that are available, with their score, may be saved. Potential sellers may be notified in parallel, e.g., with a maximum, e.g., max <NUM> at a time. These offerings can be accepted, rejected, a negotiation can be started, or they can expire, etc. The list of active orders may be updated each time it does not reach the max parallelism.

<FIG> shows an example the process of searching, matching and executing a trade on embodiment of the marketplace application. In an embodiment, the marketplace application maintains an active query queue. For example, a buyer may start by creating a query on the marketplace. The query may be added to a list of active queried in the marketplace, e.g., the active query queue. The active query queue may be be executed periodically and/or as a response to adding a query to the queue, and/or using a job queue runner. The active query may be executed against the system using parameters which may be set by the user, e.g., based on, e.g., card, distance, price, etc. For example, each result may get a score and may be added as an Offer linked to the query.

Offers with the highest score added to a query may be be activated and presented to the owner of the item associated with the offer. This person or entity is called a potential seller. For example, this can be preformed by a different process, which may be executed periodically, as a response to adding an offer to a query, as a response to decline another offer, and/or using a job queue runner, etc. In an embodiment, the maximum number of simultaneously active offers can be limited, e.g., in order to reduce the number of fulfilled/accepted orders still presented to the potential sellers. If a potential seller receives too many offers he is not able to accept due to the fact that it was already accepted by someone else, it is likely that the potential seller will deem the notifications as less valuable and may not even respond to offers at all because of disappointment.

When an offer is activated, a notification is sent to the potential seller. This notification may be in the form of a push notification, email, SMS, etc. The potential seller can open the offer in the marketplace using an app or web application. The potential seller may have various options to respond to this offer. For example, his options may include one or more of:.

If the potential seller does not respond within a set amount of time, the offer may be marked as "expired". The ratio or number of expired offers may be used for better matching in the future. If another potential seller has accepted an offer of a query, all other offers of that query may be marked as "taken". This status does not penalize the potential seller in the matching and scoring algorithm.

If the buyer decides to cancel his query, all open offers will be marked as "cancelled". This status does not penalize the potential seller but can penalize the buyer in the matching and scoring algorithm. An example may be limiting the number of simultaneously open offers for a query.

<FIG> schematically shows an example of an embodiment of a playing card. For example, the tag may be embedded in the card.

The technology described herein for playing card may also be applied to other physical objects. <FIG> schematically shows an example of an embodiment of a card binder. For example, a tag like the one used in a playing card may be embedded in a cover, e.g., a front cover or inside cover, etc. This allows the verification or transferring of card binders. Using the same technology, one could scan a folder. <FIG> schematically shows an example of an embodiment of a shoe, in this case a sneaker, with a tag embedded therein. All the embodiments discussed for playing cards could be modified to sneakers or binders.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments.

Use of the verb 'comprise' and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article 'a' or 'an' preceding an element does not exclude the presence of a plurality of such elements. Expressions such as "at least one of" when preceding a list of elements represent a selection of all or of any subset of elements from the list. For example, the expression, "at least one of A, B, and C" should be understood as including only A, only B, only C, both A and B, both A and C, both B and C, or all of A, B, and C.

Claim 1:
A playing card system (<NUM>) arranged to authenticate a playing card for playing a card game, the playing card system comprising a playing card (<NUM>), a playing card authentication device (<NUM>), and a playing card authentication server (<NUM>), wherein
A: the playing card (<NUM>) comprises
- an electronic memory (<NUM>) storing authentication data (<NUM>),
- an antenna (<NUM>) arranged for wireless communication,
- a processing circuit (<NUM>) arranged to
- wirelessly receive a digital command over the antenna from the electronic playing card authentication device,
- create an authentication token in response to receiving an authentication command, the creating comprising reading the authentication data from the memory and applying a cryptographic function thereto,
- wirelessly transmit the authentication token to the device through the antenna,
B: the playing card authentication device (<NUM>) is arranged for verifying the authenticity of the playing card, the playing card authentication device comprises
- a communication unit (<NUM>) arranged to communicate over a computer network to the playing card authentication server,
- an antenna (<NUM>) arranged for wireless communication with the playing card,
- a processing circuit (<NUM>) arranged to
- wirelessly send a digital authentication command over the antenna to the playing card,
- receive from the playing card an authentication token in response to the digital authentication command,
- send the authentication token to the authentication server through the communication unit, and
- receive from the authentication server information on the authenticity of the playing card,
C: the playing card authentication server (<NUM>) is arranged for verifying the authenticity of the playing card, the playing card authentication server comprises
- an electronic memory (<NUM>) for storing authentication data,
- a communication unit (<NUM>) arranged to communicate over the computer network with the playing card authentication device,
- a processing circuit (<NUM>) arranged to
- receive from the playing card authentication device the authentication token,
- verify the authentication token with the authentication data stored in the memory of the playing card authentication server, and
- if said verification succeeded, sending information indicating the authenticity to the playing card authentication device.