Devices, system and method for electronic cashless payment

Abstract

The invention relates to a data communication device (110) for performing an electronic payment transaction. The data communication device (110) comprises at least one processor (111), which is designed to execute a payment application (111a) and an ID application (111b), and a communication interface (113), which is designed to communicate with a trust centre server arrangement (130) and a cash ledger (150). The payment application (111a) is designed to transmit a transaction ID and a decentralized identity, DID, of a user (110a) of the data communication device (110) to a payment agent (131a) of the trust centre server arrangement (130). The ID application (111b) is designed to respond to a request from an ID agent (131b) of the trust centre server arrangement (130), which request contains the DID, by transmitting signed user credentials of the user (110a) of the data communication device (110) to the ID agent (131b) of the trust centre server arrangement (130). The payment application (111a) is also designed to receive a signature of the transaction ID from the payment agent (131a) of the trust centre server arrangement (130) and to transmit the signature of the transaction ID to the cash ledger (150) in order to enter the electronic payment transaction with the signature of the transaction ID in the cash ledger (150).

Description

[0001] Devices, systems and methods for electronic cashless payment

[0002] The present invention relates to devices, a system and methods for electronic cashless payment.

[0003] With increasing digitalization, cashless payment instruments are increasingly gaining traction, particularly those based on electronic payment processing methods. Cashless payments involve the transfer of payment instruments without the transfer of cash. Cash payments involve the exchange of cash, i.e., banknotes or coins, between the payer and the payee, whereas cashless payments do not involve such an exchange of cash.

[0004] Cash, for example, has the advantage of being available to everyone and can be used quickly and anywhere. For example, cash-based payment processing doesn't require a bank account. Furthermore, cash is often valued by its owners as a store of value. Cashless payment methods, on the other hand, have the advantage of enabling efficient payment processing even when the payer and payee are located far away, as is the case with online purchases, for example.

[0005] In cash transactions, the anonymity of the parties involved is essentially preserved. Cashless electronic payment methods can also be carried out anonymously; however, it may be necessary, for example, due to legal regulations, to record the identities of the parties involved—i.e., the payer and the payee—above certain amounts so that they can be traced. With cashless electronic payment methods based on a blockchain, such as Bitcoin, such a traceability option is generally not available.

[0006] The object of the present invention is to create a concept for electronic cashless payment that allows, if necessary, tracking of the identities of the parties involved, i.e., the payer and the payee. This object is achieved by the features of the independent claims. Advantageous embodiments are the subject of the dependent patent claims, the description, and the figures.

[0007] The embodiments of the invention described here are based on the idea that, for carrying out a cashless electronic transaction using a data communication device, for example, a smartphone, a trust service provider, in particular a trust center, verifies the identity of the payer, stores the payer's identity in a database together with a transaction ID, and digitally signs the transaction ID so that the signed transaction ID is stored by the data communication device on a money ledger. According to one embodiment, the trust center can link a transaction to the payer's identity if the transaction amount exceeds a threshold.For a transaction whose amount does not exceed the threshold, the data communication device can deposit the transaction without involving the trust center, meaning the transaction can be carried out completely anonymously. By linking a transaction to the identity of the payer through the trust center, the anonymity of a transaction on the money ledger can be maintained, yet can be traced if necessary.

[0008] According to a first aspect, a data communication device for executing an electronic payment transaction is provided. The data communication device comprises at least one processor configured to execute a payment application and an ID application, as well as a communication interface configured to communicate with a trust center server arrangement and a money ledger. The payment application is configured to send a transaction ID and a decentralized identity, DID, of a user of the data communication device to a payment agent of the trust center server arrangement. The ID application is configured to send signed user credentials of the user of the data communication device to the ID agent of the trust center server arrangement in response to a request containing the DID from an ID agent of the trust center server arrangement.The payment application is further configured to receive a signature of the transaction ID from the payment agent of the trust center server arrangement and to send the signature of the transaction ID to the money ledger in order to record the electronic payment transaction with the signature of the transaction ID on the money ledger.

[0009] In one embodiment, the payment application is configured to execute a further electronic payment transaction whose amount is less than a threshold value, sending a further transaction ID of the further electronic payment transaction to the money ledger without a signature of the further transaction ID in order to post the electronic payment transaction with the further transaction ID and without a signature of the further transaction ID on the money ledger.

[0010] In one embodiment, the payment application is further configured to generate the transaction ID and / or to receive the DID of the user of the data communication device from the ID application upon request.

[0011] In one embodiment, the ID application is further configured, in response to the request of the ID agent of the trust center server arrangement, to send zero-knowledge proof data to the ID agent of the trust center server arrangement in order to verify the signed user credentials of the user of the data communication device.

[0012] In one embodiment, the payment application is further configured to send a further DID of a further user of a further data communication device, along with the transaction ID and the DID of the user of the data communication device, to the payment agent of the trust center server arrangement. In one embodiment, the further user of the further data communication device is the payment recipient.

[0013] In one embodiment, the data communication device is a mobile and portable data communication device, in particular a smartphone.

[0014] According to a second aspect, a method for operating a data communication device for executing an electronic payment transaction is provided, wherein the data communication device comprises at least one processor configured to execute a payment application and an ID application, as well as a communication interface configured to communicate with a trust center server arrangement and a money ledger. The method comprises the following steps:

[0015] Sending a transaction ID and a decentralized identity, DID, of a user of the data communication device from the payment application to a payment agent of the trust center server arrangement;

[0016] Sending signed user credentials of the user of the data communication device from the ID application to an ID agent of the trust center server arrangement, in response to a request containing the DID from the ID agent of the trust center server arrangement;

[0017] Receiving a signature of the transaction ID from the payment agent of the trust center server arrangement by the payment application; and

[0018] Sending the transaction ID signature from the payment application to the money ledger in order to record the electronic payment transaction with the transaction ID signature on the money ledger.

[0019] According to a third aspect, a trust center server arrangement for executing an electronic payment transaction is provided. The trust center server arrangement comprises at least one processor configured to execute a payment agent and an ID agent, a communication interface configured to communicate with a data communication device, and a memory for storing electronic data. The payment agent is configured to receive a transaction ID and a decentralized identity, DID, of a user of the data communication device from a payment application of the data communication device. The ID agent is configured to receive the signed user credentials of the user of the data communication device from an ID application of the data communication device in response to a request from the payment agent containing the DID for user credentials of the user of the data communication device.The payment agent is further configured to receive the user credentials of the user of the data communication device and to store them in the memory together with the transaction ID. The payment agent is further configured to sign the transaction ID and send the signed transaction ID to the payment application of the data communication device in order to be able to record the electronic payment transaction with the signature of the transaction ID on a money ledger. In one embodiment, the communication interface is further configured to communicate with an ID ledger, and the ID agent is further configured to receive zero-knowledge proof data from the ID application of the data communication device and to verify the signed user credentials of the user of the data communication device using the zero-knowledge proof data and the ID ledger.

[0020] According to a fourth aspect, a method for operating a trust center server arrangement for executing an electronic payment transaction is provided, wherein the trust center server arrangement comprises at least one processor configured to execute a payment agent and an ID agent, a communication interface configured to communicate with a data communication device, and a memory for storing electronic data. The method comprises the following steps:

[0021] Receiving a transaction ID and a decentralized identity, DID, of a user of the data communication device from a payment application of the data communication device by the payment agent;

[0022] Obtaining signed user credentials of the user of the data communication device from an ID application of the data communication device by the ID agent in response to a request from the payment agent containing the DID for the user credentials of the user of the data communication device;

[0023] Obtaining the user credentials of the user of the data communication device by the payment agent;

[0024] Storing the user credentials of the user of the data communication device together with the transaction ID by the payment agent in the memory; and sending the signed transaction ID from the payment agent to the payment application of the data communication device in order to be able to record the electronic payment transaction with the signature of the transaction ID on a money ledger.

[0025] According to a fifth aspect, a system for carrying out an electronic payment transaction is provided, the system comprising a plurality of data communication devices according to the first aspect and a trust center server arrangement according to the third aspect.

[0026] The various aspects of the invention can be implemented in hardware and / or software. Further embodiments are explained in more detail with reference to the accompanying figures. They show:

[0027] Fig. 1 is a schematic diagram of an electronic payment system according to an embodiment with a data communication device according to an embodiment and a trust center server arrangement according to an embodiment;

[0028] Fig. 2 is a signaling diagram illustrating the interaction of the components of the system of Fig. 1 according to one embodiment;

[0029] Fig. 3 is a flowchart illustrating steps of a method for operating a data communication device according to an embodiment; and

[0030] Fig. 4 is a flowchart illustrating steps of a method for operating a trust center server arrangement according to an embodiment.

[0031] Elements of the following embodiments described in detail which correspond to one another are identified by the same reference numerals.

[0032] A "blockchain" is understood here and below to be an ordered data structure comprising a multitude of interconnected data blocks. In particular, a blockchain is understood to be an ordered data structure in which each block (except the first block) contains a check value, for example, a hash value, of its predecessor block. Thus, the validity of all its predecessor blocks can be checked and, if necessary, confirmed based on each block. The concept of a blockchain was described, for example, in a 2008 white paper on Bitcoin under the pseudonym Satoshi Nakamoto ("Bitcoin: Peer-to-Peer Electronic Cash System" (https: / / bitcoin.org / bitcoin.pdf)). The blockchain described therein consists of a series of data blocks, each of which contains one or more entries or transactions and is provided with a checksum in the form of a hash value.For example, additional blocks of the blockchain are generated in a computationally intensive process known as mining. These additional blocks are then added to the blockchain and distributed to all participants, or nodes, via a network.

[0033] Embodiments can have the advantage that the blockchain offers a high degree of security against subsequent manipulation by storing cryptographic checksums, i.e., hash values, of the previous block in each subsequent block. The chaining of the blocks can then be verified using these root hash values. Each block of the blockchain contains the hash of the entire previous block header in its header. This clearly defines the order of the blocks, creating a chain structure. By chaining the individual blocks together in this way, subsequent modification of previous blocks or individual entries is virtually impossible, since this would require the hash values ​​of all subsequent blocks to be recalculated in a short period of time.

[0034] According to one embodiment, the blockchain is a blockchain in which only a selected group of participants has authorization to add valid blocks. Such authorization can be verified, for example, by means of a signature using a private cryptographic key. The private cryptographic key can belong to an asymmetric key pair, which also includes a public cryptographic key with which the signature can be verified. The asymmetric key pair can also be associated, for example, with a certificate that proves authorization to create a valid block of the blockchain. This certificate can also be associated with a public key authentication (PKI), which verifies the authenticity of the certificate.According to another embodiment, a public key can be stored in the blockchain in an initialization entry for additional participants to be added to the selected group. These public keys can be used to verify whether block signatures, and thus the corresponding blocks themselves, are valid. Public keys of original participants in the selected group can be stored, for example, in a genesis block of the blockchain.

[0035] For example, the blockchain managed by a central bank is a public blockchain that is managed on the central bank's blockchain servers. For example, new blocks are added exclusively by these blockchain servers managed by the central bank. In this case, computationally intensive processes for adding additional blocks can be eliminated. For example, adding additional blocks requires only a signature with a signature key assigned to the central bank.

[0036] A trust center represents a trusted third party that can certify the identity of the communication partner in electronic communication processes. For example, in electronic communication in connection with electronic signatures, a trust center can issue certificates that can be used to certify the identity of the communication partner.

[0037] A "communication interface" or "communication interface" is understood here, for example, to be an interface via which data can be received and sent, whereby the communication interface can be configured as contact-based or contactless.

[0038] Communication can, for example, take place over a network. A "network" here refers to any transmission medium with a connection for communication, in particular a local connection or a local network, especially a local area network (LAN), a private network, especially an intranet, and a digital private network (Virtual Private Network - VPN).

[0039] For example, a computer system may have a standard wireless interface for connecting to a WLAN. It may also be a public network, such as the Internet. Depending on the design, this connection may also be established via a cellular network.

[0040] A "processor" is understood here and below to mean a logic circuit that serves to execute program instructions. The logic circuit can be implemented on one or more discrete components, in particular on a chip. A processor comprises, for example, an arithmetic unit, a control unit, registers, and data lines for communication with other components. In particular, a "processor" is understood to mean a microprocessor or a microprocessor system comprising multiple processor cores and / or multiple microprocessors. The processor is designed to execute program instructions that are stored, for example, in a memory in order to carry out the operations and methods described herein. A "memory" is understood here, in particular, to mean a non-volatile memory. A "non-volatile memory" is understood here, for example, to mean an electronic memory for the permanent storage of data.Non-volatile memory can be configured as non-modifiable memory, also known as read-only memory (ROM), or as modifiable memory, also known as non-volatile memory (NVM). In particular, this can be an EEPROM, such as a Flash EEPROM, also known as Flash. Non-volatile memory is characterized by the fact that the data stored on it is retained even after the power supply is turned off.

[0041] A "protected memory area" is understood here to be an area of ​​an electronic memory to which access, i.e. read access or write access, is only possible via a processor of a security element.

[0042] For example, no external access is possible to the protected memory area, i.e. data can neither be brought in from the outside nor output to the outside. For example, data can be read out from the protected memory area via the processor. For example, data can be brought into the protected memory area from the outside via the processor. According to embodiments, access from or via the processor coupled to the memory is only possible if a necessary condition is met. This can be, for example, a cryptographic condition, in particular successful authentication and / or a successful authorization check. Such a check can, for example, be based on an electronic signature with a signature key.

[0043] Asymmetric key pairs are used in a variety of cryptosystems and also play an important role in signing electronic data. An asymmetric key pair consists of a public key, which is used to encrypt and / or decrypt data and may be shared with third parties, and a private key, which is used to encrypt and / or decrypt data and must generally be kept secret. The public key allows anyone to encrypt data for the owner of the private key and to verify digital signatures created with the private key. A private key allows its owner to decrypt data encrypted with the public key or to create digital signatures. A signature created with a private key can be verified with the corresponding public key.

[0044] The creation of a digital signature, hereinafter referred to simply as a "signature," is a cryptographic process in which an additional data value, referred to as a "signature," is calculated for any given piece of data. A signature can, for example, be a hash value of the source data encrypted with a private cryptographic key.

[0045] A security element is understood here, for example, to be an electronic component that comprises a processor and a memory, and to which only certain predefined accesses are permitted. For example, only certain data values, which are stored in certain areas of the memory, can be read. For example, data values ​​stored in a protected memory area cannot be read. For example, writing a data value to the memory of the security element requires a digital signature, the verification key for which is stored in the security element. For example, only the processor has write permissions to write data to a protected memory area.

[0046] The security element further provides, for example, cryptographic core routines in the form of cryptographic program instructions with cryptographic algorithms for signature creation and / or verification, key generation, and / or random number generation and can further serve as a secure storage for cryptographic keys.

[0047] For example, at least parts of the security element are signed. Before the security element is used, it is checked whether the signature(s) are valid. If one of the signatures is invalid, use of the security element is blocked, for example.

[0048] For example, the security element has physically restricted access options. In addition, the security element can have additional measures against misuse, in particular against unauthorized access to data in the memory of the security element. For example, the means for protecting the security element against unauthorized manipulation comprise mechanical means which are intended, for example, to prevent the security element or its parts from being opened, or which, in the event of an attempt to tamper with the security element, render it unusable, for example by causing data loss. For example, at least parts of the security element can be enclosed, cast in and / or laminated in a material whose attempted removal leads to the inevitable destruction of the corresponding parts of the security element.

[0049] Figure 1 shows a system 100 for the traceable execution of electronic cashless payments between a first data communication device 110 of a payer user 110a and a second data communication device 120 of a payee. The first and / or second data communication device 110, 120 can each be a mobile and portable data communication device 110, 120, in particular a smartphone 110, 120. In the embodiments described below, the data communication devices 110, 120 are exemplary smartphones 110, 120.

[0050] In the embodiment illustrated in Figure 1, the smartphone 110 of the payer user 110a and the smartphone 120 of the payee each comprise one or more processors 111, 121, a communication interface 113, 123 for wireless and / or wired communication via a communication network, and a memory 115, 125 for storing electronic data. The smartphones 110, 120 can each comprise a security element, e.g., a virtual or physical SIM card, which is configured to store security-critical data and / or perform security-critical operations, in particular cryptographic operations.

[0051] As shown in Figure 1, the processor 111, 121 of the respective smartphone 110, 120 is designed to execute a payment application 111a, 121a and an ID application 111b, 121b, the function and interaction of which with one another and with the other components of the system 100 is described in detail below with further reference to Figure 2.

[0052] In addition to the smartphone 110 of the payer user 110a and the

[0053] Smartphone 120 of the payee, the system 100 includes a trust center

[0054] Server arrangement 130, an ID ledger 140 for self-determined identities (Self-Sovereign Identity (SSI); therefore also referred to as "SSI ledger" 140 in Figure 1), a money ledger 150, for example a blockchain 150, and a central bank or a central bank server 160 for managing the money ledger 150. The trust center server arrangement 130 can comprise one or more servers, with one or more processors 131, a communication interface 133 for wireless and / or wired communication via a communication network and a memory 135 for storing electronic data.

[0055] As shown in Figure 1, the at least one processor 131 of the trust center server arrangement 130 is designed to execute a payment agent 131a (or payment service 131a) and an ID agent 131b (or ID service 131b), the function and interaction of which with one another and with the other components of the system 100 are described in detail below with further reference to Figure 2.

[0056] The money ledger 150 can, for example, be implemented on one or more blockchain servers. In other words, the blockchain servers can be part of a money ledger network 150 and thus be blockchain nodes of the money ledger 150. The blockchain servers and / or the money ledger 150, i.e., the blockchain network 150, can be managed, for example, by a central bank 160. If the central bank 160 is a central bank 160 to which several countries belong, the money ledger 150 can, for example, comprise one or more blockchain servers per country.

[0057] Figure 2 illustrates the interaction of the components of the system 100 shown in Figure 1 according to one embodiment.

[0058] The payer user 110a wishes to pay a certain amount to the payee via their smartphone 110 using their smartphone 120. To do so, in step 201 of Figure 2, the user 110a starts the payment application 111a (referred to as the "payment app" in Figure 2) on their smartphone 110.

[0059] In the embodiment shown in Figure 2, the payment application 111a implemented by the processor 111 first checks the amount to be paid. If this amount is higher than a threshold (for example, a legally defined threshold), the smartphone 110 performs the further steps shown in Figure 2 (step 203 of Figure 2). Otherwise, i.e., if the amount to be paid is not higher than the threshold, the payment transaction can be carried out without the trust center 130 and recorded on the money ledger 150 in an essentially known manner. However, the invention also provides embodiments in which this check is omitted, and the steps described below are carried out regardless of the amount to be paid.

[0060] Since, in the example shown in Figure 2, the amount to be paid is greater than the threshold, the payment application 111a implemented by the processor 111 generates a request in step 205 of Figure 2 and sends it via the communication interface 113 to the trust center 130, in particular the payment agent 131a (labeled as "TSE agent" 131a in Figure 2) of the trust center 130, in order to receive a transaction ID digitally signed by the trust center 130. In response to the request in step 205, the payment agent 131a, in turn, sends a request to the payment application 111a for the transaction ID and a decentralized ID for the user 110a of the smartphone 110 in step 207 of Figure 2. In one embodiment, the transaction ID can be generated by the payment application 111a of the smartphone.

[0061] In the steps 209 of Figure 2 running within the smartphone 110, the payment application 111a first sends a request to the ID application 111b and receives from it as a response the decentralized ID (DID; also known in English as "Decentralized Identifier") of the payer user 110a of the smartphone 110.

[0062] In step 210 of Figure 2, the payment application 111a of the smartphone 110 sends the DID and the transaction ID received from the ID application 111b to the payment agent 131a of the trust center 130.

[0063] In step 211 of Figure 2, the payment agent 131a of the trust center 130 sends a request for user credentials (or user information) of the user 110a to the ID agent 131b of the trust center 130. The request contains the DID received from the ID application 111b of the smartphone 110. The ID agent 131b essentially serves to automatically verify identities in the SSI ledger (or ID ledger) 140, which is based on distributed ledger technology (DLT). In step 213 of Figure 2, the ID agent 131b of the trust center 130 sends a request for the user credentials to the ID application 111b of the smartphone 110, ie for the user information for verifying the identity of the user 110a of the smartphone 110 by means of the SSI ledger 140. The request contains the DID originally received from the ID application 111b.

[0064] In step 215 of Figure 2, the ID application 111b of the smartphone 110 signs the user credentials or user information with a private key of the smartphone 110. Such a private key can be stored, for example, in a secure memory area of ​​a security element, such as a virtual or physical SIM card of the smartphone 110. As already described above, security-critical cryptographic operations of the ID application 111b and / or payment application 111a can be performed in such a security element.

[0065] In step 217, the ID application 111b of the smartphone 110 proves the authenticity of the user credentials or user information transmitted in step 215 by means of a zero-knowledge proof (ZKP).

[0066] In step 219 of Figure 2, the ID agent 131b of the trust center 130 obtains data from the ID ledger 140 to confirm or verify the ZKP of step 217 by downloading this data from the ID ledger 140 (step 221 of Figure 2).

[0067] After the ZKP has been confirmed by the ID agent 131b of the trust center 130 (based on which the ID agent 131a can trust the user credentials), the ID agent 131b of the trust center 130 sends the user credentials to the payment agent 131a in step 223 of Figure 2. The payment agent 131a then stores the signed transaction ID together with the user credentials in a database 135a implemented in the memory 135 (step 225 of Figure 2). In one embodiment, the payment agent 131a can also assign an identification number for this purpose and link it to the transaction ID.

[0068] In step 227, the payment agent 131a of the trust center 130 sends the signed

[0069] Transaction ID to the payment application 111a of the smartphone 110. Thus, step 227 ultimately represents the response of the trust center 130 to the signed transaction ID requested in step 205.

[0070] To complete the payment transaction, in step 229 of Figure 2, the payment application 111a sends the transaction data, i.e., in particular, the transaction ID and the amount, as well as the signature of the transaction ID, to the money ledger 150, where this data is posted or stored to be available to the central bank server 160 for tracking if necessary. The payment process is thus completed. Optionally, the identity of the payment recipient, i.e., the user of the additional smartphone 120, can also be recorded by the payment application 111a also obtaining the DID of the user of the additional smartphone 120. In this case, the identity agent 131b of the trust center 130 would establish two separate connections, namely one to the smartphone 110 of the payer user 110a and the other to the smartphone of the payment recipient.

[0071] Figure 3 shows a flowchart illustrating steps of a method 300 for operating the data communication device 110 according to one embodiment. The method 300 includes the following steps:

[0072] Sending 301 a transaction ID and a decentralized identity, DID, of the user 110a of the data communication device 110 from the payment application 111a to a payment agent 131a of the trust center server arrangement 130;

[0073] Sending 303 signed user credentials of the user 110a of the data communication device 110 from the ID application 111b to an ID agent 131b of the trust center server arrangement 130, in response to a request containing the DID from the ID agent 131b of the trust center server arrangement 130;

[0074] Receiving 305 a signature of the transaction ID from the payment agent 131b of the trust center server arrangement 130 by the payment application 111a; and sending 307 the signature of the transaction ID from the payment application 111a to the money ledger 150 in order to post the electronic payment transaction with the signature of the transaction ID on the money ledger 150.

[0075] Figure 4 shows a flowchart illustrating steps of a method 400 for operating the trust center server arrangement 130 according to one embodiment.

[0076] The method 400 comprises the following steps: receiving 401 a transaction ID and the decentralized identity, DID, of the user 110a of the data communication device 110 from a payment application 111a of the data communication device 110 by the payment agent 131a;

[0077] Obtaining 403 signed user credentials of the user 110a of the data communication device 110 from an ID application 111b of the data communication device 110 by the ID agent 131b, in response to a request containing the DID from the payment agent 131a for the user credentials of the user 110a of the data communication device 110;

[0078] Received 405 of the user credentials of user 110a of the

[0079] Data communication device 110 by the payment agent 131a;

[0080] Storing 407 the user credentials of the user 110a of the data communication device 110 together with the transaction ID by the payment agent 131a in the memory 135; and

[0081] Sending 409 the signed transaction ID from the payment agent 131a to the payment application 111a of the data communication device 110 in order to be able to record the electronic payment transaction with the signature of the transaction ID on the money ledger 150.

[0082] LIST OF REFERENCE SYMBOLS

[0083] 100 Electronic payment system

[0084] 110 Data communication device of the payer

[0085] 110a Paying User

[0086] 111 processor

[0087] 111a Payment application

[0088] 111b ID application

[0089] 113 Communication interface

[0090] 115 storage

[0091] 120 Data communication device of the payee

[0092] 121 processor

[0093] 121a Payment Application

[0094] 121b ID application

[0095] 123 Communication interface

[0096] 125 storage

[0097] 130 Trust Center Server Arrangement

[0098] 131 processor

[0099] 131a Payment Agent

[0100] 131b ID agent

[0101] 133 Communication interface

[0102] 135 storage

[0103] 135a Database

[0104] 140 ID ledgers

[0105] 150 money ledgers

[0106] 160 Central Bank

Claims

PATENT CLAIMS 1. Data communication device (110) for executing an electronic payment transaction, wherein the data communication device (110) comprises: at least one processor (111) configured to execute a payment application (111a) and an ID application (111b); and a communication interface (113) configured to communicate with a trust center server arrangement (130) and a money ledger (150); wherein the payment application (111a) is configured to send a transaction ID and a decentralized identity, DID, of a user (110a) of the data communication device (110) to a payment agent (131a) of the trust center server arrangement (130);wherein the ID application (111b) is configured to send signed user credentials of the user (110a) of the data communication device (110) to the ID agent (131b) of the trust center server arrangement (130) in response to a request containing the DID from an ID agent (131b) of the trust center server arrangement (130); wherein the payment application (111a) is further configured to receive a signature of the transaction ID from the payment agent (131a) of the trust center server arrangement (130) and to send the signature of the transaction ID to the money ledger (150) in order to record the electronic payment transaction with the signature of the transaction ID on the money ledger (150).

2. Data communication device (110) according to claim 1, wherein the payment application is configured to execute a further electronic payment transaction, the amount of which is less than a threshold, to send a further transaction ID of the further electronic payment transaction without a signature of the further transaction ID to the money ledger (150) in order to record the electronic payment transaction with the further transaction ID and without a signature of the further transaction ID on the money ledger (150).

3. Data communication device (110) according to claim 1 or 2, wherein the payment application (111a) is further configured to generate the transaction ID and / or to obtain the DID of the user 110a of the data communication device (110) from the ID application (111b) upon request.

4. Data communication device (110) according to one of the preceding claims, wherein the ID application (111b) is further configured to send zero-knowledge proof data to the ID agent (131b) of the trust center server arrangement (130) in response to the request of the ID agent (131b) of the trust center server arrangement (130) in order to verify the signed user credentials of the user (110a) of the data communication device (110).

5. Data communication device (110) according to one of the preceding claims, wherein the payment application (111a) is further configured to send a further DID of a further user of a further data communication device (120) together with the transaction ID and the DID of the user (110a) of the data communication device (110) to the payment agent (131a) of the trust center server arrangement (130).

6. Data communication device (110) according to one of the preceding claims, wherein the data communication device (110) is a mobile and portable data communication device (110), in particular a smartphone (110).

7. Method (300) for operating a data communication device (110) for executing an electronic payment transaction, wherein the data communication device (110) comprises at least one processor (111) configured to execute a payment application (111a) and an ID application (111b), and a communication interface (113) configured to communicate with a trust center server arrangement (130) and a money ledger (150), wherein the method (300) comprises: Sending (301) a transaction ID and a decentralized identity, DID, of a user (110a) of the data communication device (110) from the payment application (111a) to a payment agent (131a) of the trust center server arrangement (130); Sending (303) signed user credentials of the user (110a) of the data communication device (110) from the ID application (111b) to an ID agent (131b) of the trust center server arrangement (130) in response to a DID-containing request from the ID agent (131b) of the trust center server arrangement (130); Receiving (305) a signature of the transaction ID from the payment agent (131a) of the trust center server arrangement (130) by the payment application (111a); and Sending (307) the signature of the transaction ID from the payment application (111 a) to the money ledger (150) to record the electronic payment transaction with the signature of the transaction ID on the money ledger (150).

8. Trust center server arrangement (130) for executing an electronic payment transaction, the trust center server arrangement (130) comprising: at least one processor (131) configured to execute a payment agent (131a) and an ID agent (131b); a communication interface (133) configured to communicate with a data communication device (110); and a memory (135) for storing electronic data; wherein the payment agent (131a) is configured to receive a transaction ID and a decentralized identity, DID, of a user (110a) of the data communication device (110) from a payment application (111a) of the data communication device (110);wherein the ID agent (131b) is trained to obtain, in response to a DID-containing request from the payment agent (131a) for user credentials of the user (110a) of the data communication device (110), the signed user credentials of the user (110a) of the data communication device (110) from an ID application (111b) of the data communication device (110); wherein the payment agent (131a) is further trained to receive the user credentials of the user (110a) of the data communication device (110) and to store them together with the transaction ID in the memory (135); and wherein the payment agent (131a) is further trained to sign the transaction ID and to send the signed transaction ID to the payment application (111a) of the data communication device (110) in order to be able to record the electronic payment transaction with the signature of the transaction ID on a money ledger (150).

9. Trust center server arrangement (130) according to claim 8, wherein the communication interface (133) is further configured to communicate with an ID ledger (140) and wherein the ID agent (131b) is further configured to receive zero-knowledge proof data from the ID application (111b) of the data communication device (110) and to verify the signed user credentials of the user (110a) of the data communication device (110) using the zero-knowledge proof data and the ID ledger (140).

10. Method (400) for operating a trust center server arrangement (130) for executing an electronic payment transaction, wherein the trust center server arrangement (130) comprises at least one processor (131) configured to execute a payment agent (131a) and an ID agent (131b), a communication interface (133) configured to communicate with a data communication device (110), and a memory (135) for storing electronic data, wherein the method (400) comprises: Receiving (401) a transaction ID and a decentralized identity, DID, of a user (110a) of the data communication device (110) from a payment application (111a) of the data communication device (110) by the payment agent (131a); Received (403) signed user credentials of the user (110a) of the data communication device (110) from an ID application (111b) of the data communication device (110) by the ID agent (131b) in response to a DID-containing request from the payment agent (131a) for the user credentials of the user (110a) of the data communication device (110); Obtain (405) the user credentials of the user (110a) of the Data communication device (110) by the payment agent (131a); Storing (407) the user credentials of the user (110a) of the data communication device (110) together with the transaction ID by the payment agent (131a) in the memory (135); and Sending (409) the signed transaction ID from the payment agent (131a) to the payment application (111a) of the data communication device (110) in order to record the electronic payment transaction with the signature of the transaction ID on a money ledger (150).

11. System (100) for executing an electronic payment transaction, the system comprising: a plurality of data communication devices (110) according to any one of claims 1 to 6; and a trust center server arrangement (130) according to any one of claims 8 or 9.

12. Computer program comprising program code for executing the method (300) according to claim 7 and / or the method (400) according to claim 10 when the computer program is executed on a computer.

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