Apparatus, method, and program for obtaining authenticated feedback using non-transferable non-fungible tokens

Abstract

The present disclosure relates to a method for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity. The method includes receiving feedback of the first digital identity regarding the published content and a reference identification of the published content. The method further includes receiving a cryptographic proof including a verifiable credential of the first digital identity, as well as receiving a digital address of the second digital identity. Furthermore, the method includes minting a non-transferable non-fungible token, NFT, on a blockchain network, wherein the non-transferable NFT comprises the verifiable credential of the first digital identity and the reference identification, as well as issuing the non-transferable NFT to the digital address of the second digital identity.

Description

[0001] APPARATUS, METHOD, AND PROGRAM FOR OBTAINING AUTHENTICATED

[0002] FEEDBACK USING NON-TRANSFERABLE NON-FUNGIBLE TOKENS.

[0003] Field

[0004] The present disclosure relates to methods, apparatuses, and programs for obtaining authenticated feedback to published content using non-transferable non-fungible tokens.

[0005] Background

[0006] Social media or other interactive online platforms provide response or reaction mechanisms which allow users to respond to content through features such as ratings, comments, so-called “likes”, or other types of responses or reactions. One issue is that individuals or entities can submit multiple responses to the same content using several aliases, accounts and / or email addresses, rendering these responses inauthentic. Response mechanisms based on such potentially inauthentic responses are not reliable.

[0007] Digital verifiable credentials may be used to verify the authenticity of responses to published content. However, a party claiming to have thousands of authentic responses, such as reviews or “likes”, must have each response verified, which is not scalable with standard methods. Another problem is that such verifications need to be continually repeated, since each response may be revoked at any time.

[0008] Thus, there is a demand to improve the scalability for credential verification.

[0009] Summary

[0010] This demand is met by a method and an apparatus for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity, a program, and a non-transitory machine-readable medium according to the independent claims. Advantageous embodiments are addressed by the dependent claims. According to a first aspect, the present disclosure proposes a method for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity. The method includes receiving a cryptographic proof including a verifiable credential of the first digital identity. The method further includes receiving feedback of the first digital identity regarding the published content and a reference identification of the published content, as well as receiving a digital address of the second digital identity. The method further includes minting a non-transferable non-fungible token, NFT, on a blockchain network. The non-trans- ferable NFT comprises the verifiable credential of the first digital identity and the reference identification. The method further includes issuing the non-transferable NFT to the digital address of the second digital identity.

[0011] According to a second aspect, the present disclosure proposes an apparatus for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity. The apparatus comprises one or more interfaces for communication and processing circuitry configured to receive feedback of the first digital identity regarding the published content and a reference identification of the published content. The processing circuitry is further configured to receive a cryptographic proof including a verifiable credential of the first digital identity, as well as a digital address of the second digital identity. Furthermore, the processing circuitry is configured to mint a non-transferable non-fungible token, NFT, comprising the verifiable credential of the first digital identity and the reference identification, and to issue the non-transferable NFT to the digital address of the second digital identity.

[0012] According to a third aspect, the present disclosure proposes a program having a program code for performing the method described above, when the program is executed on a processor or a programmable hardware.

[0013] According to a fourth aspect, the present disclosure proposes a non-transitory machine-readable medium having stored thereon a program having a program code for performing the method described above, when the program is executed on a processor or a programmable hardware. Brief description of the Figures

[0014] Some examples of apparatuses and / or methods will be described in the following by way of example only, and with reference to the accompanying figures, in which

[0015] Fig. 1 schematically illustrates an exemplary apparatus for obtaining authenticated feedback using non-transferable NFTs;

[0016] Fig. 2 illustrates the transfer of a verifiable credential from an issuer to a first digital identity and then to an apparatus;

[0017] Fig. 3 illustrates a demonstration of possession of a plurality of non-transferable NFTs to a third party verifier via an apparatus;

[0018] Fig. 4A illustrates a change of an active non-transferable NFT to an inactive non-transferable NFT based on further feedback;

[0019] Fig. 4B illustrates a change of an inactive non-transferable NFT to an active non-transferable NFT based on further feedback;

[0020] Fig. 5 illustrates a flowchart of an exemplary method for obtaining authenticated feedback using non-transferable NFTs.

[0021] Detailed Description

[0022] Some examples are now described in more detail with reference to the enclosed figures. However, other possible examples are not limited to the features of these embodiments described in detail. Other examples may include modifications of the features as well as equivalents and alternatives to the features. Furthermore, the terminology used herein to describe certain examples should not be restrictive of further possible examples. Throughout the description of the figures same or similar reference numerals refer to same or similar elements and / or features, which may be identical or implemented in a modified form while providing the same or a similar function. The thickness of lines, layers and / or areas in the figures may also be exaggerated for clarification.

[0023] When two elements A and B are combined using an “or”, this is to be understood as disclosing all possible combinations, i.e. only A, only B as well as A and B, unless expressly defined otherwise in the individual case. As an alternative wording for the same combinations, "at least one of A and B" or "A and / or B" may be used. This applies equivalently to combinations of more than two elements.

[0024] If a singular form, such as “a”, “an” and “the” is used and the use of only a single element is not defined as mandatory either explicitly or implicitly, further examples may also use several elements to implement the same function. If a function is described below as implemented using multiple elements, further examples may implement the same function using a single element or a single processing entity. It is further understood that the terms "include", "including", "comprise" and / or "comprising", when used, describe the presence of the specified features, integers, steps, operations, processes, elements, components and / or a group thereof, but do not exclude the presence or addition of one or more other features, integers, steps, operations, processes, elements, components and / or a group thereof.

[0025] A non-fungible token, NFT, is a unique digital identifier that is recorded on a blockchain network. It is used to certify ownership and authenticity, particularly since it cannot be copied, substituted, or subdivided. While typical blockchain assets like cryptocurrencies and conventional NFTs can be sold or traded, certain NFTs are non-transferable. Thus, they are tied to a specific wallet or identity. These may generally be referred to as non-transferable NFTs or non-transferable tokens (NTTs). They may also be referred to as SoulBound tokens (SBTs), since the tokens remain permanently tied to a specified digital identity, or a so-called “soul”. Non-transferable NFTs (e.g., SBTs) were introduced on the Ethereum blockchain network, but they may generally be used within any blockchain network.

[0026] Non-transferable NFTs may be tokens of certification, acting as non-transferable attributes or affiliations in digital form. This may include general credentials, memberships, qualifications, or personal achievements that cannot be sold or transferred to another indivi dual, among other uses. Non-transferable NFTs are generally used as a record of information that may be issued to a digital wallet and become intrinsically linked to a digital identity.

[0027] Applications using non-transferrableNFTs are wide-ranging and may also include verification or certification of a digital identity, as well as decentralized reputation systems. In the case of an individual or organization releasing published content, it is desired that feedback regarding the published content is genuine. It is also well known that positive responses can be inflated by programmed bots to artificially boost engagement metrics. On the other hand, the reputation of the individual or organization publishing content can be unfairly manipulated by malicious agents. In either case, an accurate impression of feedback is blocked. While solutions for verification have been proposed on a small scale, continuous verification on a larger scale poses a challenge.

[0028] The following disclosure addresses the need to verify that online feedback to published content is indeed authentic and that such authenticity can be verified on a large scale. Through the use of non-transferable NFTs with cryptographic proofs, feedback may be efficiently and continuously authenticated from a large number of sources. An apparatus enabling such use is presented in Figs. 1 to 4, with a corresponding method presented in Fig. 5.

[0029] Fig. 1 schematically illustrates an exemplary apparatus 100 for obtaining authenticated feedback from a first digital identity 200A regarding published content of a second digital identity 200B using non-transferable NFTs. Authenticated feedback regarding the published content of the second digital identity may then be obtained from a large number of digital identities, each acting as the first digital identity in the respective instance. Thus, verification is ensured for each instance of feedback.

[0030] In practice, the first and / or second digital identity can be online identities or so-called “selfsovereign identities”. Other forms of digital representation may also be used. In the context of blockchain networks, a digital identity refers to a unique representation of an individual, organization, or device in the digital realm. For representation of an individual, the identities can have one or more attributes which, e.g., comprise the age, the sex, the date of birth, and / or other personal information on the person associated with the respective digital identity. For representation of an organization, the identities can be linked to an official registration or official identification number. Each digital identity representing an individual or organization may publish content and / or provide feedback to published content.

[0031] The published content can be any digital content on an interactive public or private (social) platform. Interactive platforms may be or may comprise social media networks, electronic messengers, chat rooms, poll platforms or any other platforms which allow users to respond to its content. The platform may also be a newspaper website, a magazine website, or a blog that invites feedback to published content from the general public or a subgroup, such as by membership. In practice, the published content can comprise or correspond to an account, a profile, a post, a comment, a message, a video, an electronic / digital poll, a picture, or the like on such a platform. The second digital identity may have published the digital content, i.e., made the content available via such a platform to invite a plurality of other identities to provide feedback.

[0032] For referencing, the published content is provided with a reference ID 330, which is provided to the processing circuitry 104 with the feedback 320. The reference ID 330 may be a URL, an article ID, or a publication ID, among other examples. The feedback 320 may also come in various forms. For example, the feedback 320 can comprise or correspond to a reaction, a rating, a comment, a vote, or a “like”, among other examples. In some embodiments, the feedback 320 may include multiple portions of information, such as a star rating with a comment. In such cases, the issued NFT 210 may comprise more specific information to be displayed. In other embodiments, the feedback 320 may be a simplified positive rating, such as a thumbs up or “like”. In such cases, the NFT 210 may itself symbolize the positive feedback (i.e. act as a positive rating token, “like” token, etc.).

[0033] The apparatus 100 comprises one or more interfaces for communication (e.g., interface circuitry 102) and processing circuitry 104. The processing circuitry 104 is configured to receive the feedback 320 of the first digital identity 200A and the reference ID 330 regarding the published content, as previously described. Furthermore, the processing circuitry 104 is configured to receive a cryptographic proof 310, including a verifiable credential 312 of the first digital identity 200A, and a digital address 340 of the second digital identity 200B on the blockchain network. The processing circuitry 104 is further configured to mint a non- transferable NFT 210 comprising the verifiable credential 312 of the first digital identity 200A and the reference ID 330 and to issue the non-transferable NFT 210 to the digital address 340 of the second digital identity 200B.

[0034] The apparatus 100 is part of or connectable to a blockchain network and configured to perform the steps described above. The steps performed may be referred to as a smart contract. Generally, smart contracts are self-executing contracts with the terms of agreement directly written into code. On the blockchain network, they can automatically enforce and execute terms when predefined conditions are met. The predefined conditions may include what inputs are required and what features the minted and issued non-transferable NFTs have. This may ensure that the properties of the issued non-transferable NFTs remain consistent.

[0035] For interacting with the blockchain network and invoking the smart contract, certain javascript libraries (e.g., Web3.js, Ether.js) may be used. In some embodiments, a user wishing to provide feedback may click a user interface element on a website (e.g., a thumbs up or “like” button, a star rating, etc.). This may be provided by a web3 provider, such as MetaMask, a browser extension allowing users to interact with the Ethereum blockchain, thereby injecting a web3 instance into the browser, among other examples. The website may ask the user to connect his digital wallet to interact with the smart contract. The user interface element on the website may provide the digital address and an application binary interface of the smart contract, as well as the reference ID 330 and the digital address 340 of the second digital identity 200B (e.g., the receiver of the thumbs-up, “like”, or star rating), as well as the cryptographic proof 310 with the verifiable credential 312 so that the non-transferable NFT 210 may be minted and issued.

[0036] Assuming the cryptographic proof 310, the feedback 320, the reference ID 330, and the digital address 340 of the second digital identity 200B each meet respective predefined forms and conditions, the apparatus can be automated by means of the smart contract to mint the non- transferable NFT 210 and issue it to the specified digital address 340. Once the non-transferable NFT 210 is obtained by the second digital identity 200B, it may be visible through a blockchain explorer or a compatible wallet interface that can display such NFTs. The details of the non-transferable NFT 210, such as its origin, issuance date, and other specified attributes, may be verifiable on the blockchain network, ensuring transparency and authenticity. The non-transferable NFT 210 cannot be transferred and the record of having obtained the non-transferable NFT 210 cannot be altered by external accounts. In some instances, the record of having received the non-transferable NFT 210 is immutable, even by the holder itself.

[0037] The cryptographic proof and verifiable credential will be described in further detail with reference to Fig. 2. The accumulation of multiple non-transferable NFTs at the digital address 340 of the second digital identity 200B will be described in further detail with reference to Fig. 3.

[0038] Fig. 2 depicts how the apparatus 100 may receive the verifiable credential 312. In a first transfer, the verifiable credential 312, shown in its original form 312a and depicted as being sent from an issuer 400 with trusted authority (e.g., the government or a government agency) to the first digital identity 200A (i.e. the individual or organization represented by the first digital identity 200A). In some embodiments, the verifiable credential 312a is a government-issued ID number. The government-issued identification number may be a passport number, person ID number, a national ID number, a driver's license number, a tax identification number, an employee identification number, an insurance number, or a social security number, among other comparable examples.

[0039] Generally, the verifiable credential 312 may be provided as a form of identity verification of the first digital identity 200A. However, it may be desired to use such information for verification while not publicly displaying it (e.g., not revealing an ID number or signature). For this, the first digital identity 200 A may directly provide the cryptographic proof 310 including its verifiable credential 312 for verification. The cryptographic proof 310 is shown in a second transfer of Fig. 2, being transferred from the first digital identity 200A to the apparatus 100.

[0040] In some embodiments, the verifiable credential 312 of the first digital identity 200A may be included in the cryptographic proof 310 as a cryptographic hash value. The verifiable credential 312 of the first digital identity 200A in Fig. 1, first obtained in its original form 312a, may be transformed into a hash value form, shown as 312b. The individual or organization represented by the first digital identity 200A may perform the necessary steps to transform the verifiable credential 312 from its original form 312a into its hashed form 312b using a cryptographic hash function.

[0041] Generally, a cryptographic hash value is an output of fixed length generated by transforming an input of varied length using a cryptographic hash function. A certain input always reproduces the same output, and it is also extremely unlikely that two similar inputs to lead to the same hash value. While it is computationally simple to calculate a hash value for a given input, it is extremely computationally difficult or impossible to perform a reverse calculation. A proper hash function can ensure that the hashed verifiable credential 312b is uniquely associated with the first digital identity 200A. Generally, any (ID) number that is recognized to have a permanent association with the individual or organization may be used for generating the cryptographic hash value.

[0042] To further ensure uniqueness, the verified credential 312 can be indicative or representative of unique information or a unique combination of information about a person or organization associated with the first digital identity 200A. This may include a unique ID number, unique biometric information, information on a commercial register entry or ownership of a bank account, etc. Generally, for persons or organizations, such standards may be based on the data model for verifiable credentials of the World Wide Web Consortium (W3C). The verifiable credential 312 can also be digitally signed for making it tamper-resistant and verifiable.

[0043] A cryptographic proof generally refers to the use of cryptographic techniques for verification in a digital realm, such as blockchain systems. For example, the cryptographic proof 310 provided by the first digital identity 200A may be a zero-knowledge proof (ZKP). Generally, a ZKP allows a credential holder to present a verifiable credential without revealing the credential in its original form. Examples of ZKP types with distinct cryptographic protocols include zk-SNARK (zero-knowledge succinct non-interactive argument of knowledge) and Bullet- Proof, among other examples, such as ZK-IAK (zero-knowledge interactive argument of knowledge), NIZK (non-interactive zero-knowledge proof), Zero-knowledge set membership proof, ZKPID (zero-knowledge proof of identity), zero-knowledge proof of shuffle, NIAK (non-interactive arguments of knowledge), the Groth 16 protocol, and various Sigma protocols. Once the first digital identity 200 A has generated the cryptographic proof 310 with the hashed verifiable credential 312b, it may be transferred to the blockchain network (via the apparatus 100). This may be achieved by means of a user interface. The user interface may provide input parameters to be submitted, including the cryptographic proof 310 with the hashed verifiable credential 312b and the feedback 320. The verifiable credential 312 of the first digital identity 200A and the feedback 320 may be submitted in association with one another, so that the verifiable credential is used for not only verifying identity, but also to prove that the feedback 320 is authentic feedback of the first digital identity 200A. To establish such association, the feedback 320 and reference ID 330 may be submitted simultaneously with the cryptographic proof 310 or with a reference to the first digital identity 200 A.

[0044] For example, by providing the cryptographic proof 310 with the cryptographic hash-value 312, the verification of being a holder of an ID number may be restricted to revealing only the hashvalue, without ever revealing the ID number itself. The cryptographic proof 310 may be verified as a condition for minting and issuing the non-transferable NFT 210. As such, the continued display of the non-transferable NFT 210 can serve as a continued demonstration that the cryptographic proof has been verified.

[0045] Such verification enables continued demonstration of verification for a large number of feedback instances, as depicted in Fig. 3.

[0046] Fig. 3 depicts an accumulation of multiple non-transferable NFTs 210-1; 210-2; 210-3; 210-n at the digital address 340 of the second digital identity 200B. The apparatus 100 may be configured to mint a plurality of non-transferrable NFTs 210-1; 210-2; 210-3; 210-n, each corresponding to a respective digital identity, with each non-transferrable NFT 210-1; 210-2; 210- 3; 210-n comprising the reference identification 330 and a verifiable credential 312-1; 312-2; 312-3; 312-n for the respective digital identity. The apparatus 100 may further be configured to issue each of the plurality of non-transferrable NFTs 210-1; 210-2; 210-3; 210-n to the digital address 340 of the second digital identity 200B, as previously described.

[0047] By repeating the methods outlined in Figs. 1 and 2 for a plurality of users, the second digital identity 200B may accumulate a plurality of non-transferable NFTs 210-1; 210-2; 210-3; 210- n, each of which demonstrate its own authenticated feedback from an individual user (i.e. individual person or organization providing feedback). The second digital identity 200B is thus able to demonstrate a plurality (a large number n, possibly in the hundreds, thousands, tens of thousands, etc.) of unique digital identities. Each of the displayed non-transferable NFTs 210-1; 210-2; 210-3; 210-n correspond to an example of the first digital identity 200 A that provided the required cryptographic proof 310-1; 310-2; 310-3; 310-n (not shown) with the respective verifiable credentials 312-1; 312-2; 312-3; 312-n.

[0048] Furthermore, the apparatus 100 may be configured to display upon query each of the plurality of non-transferable NFTs 210-1; 210-2; 210-3; 210-n. For example, the apparatus 100 may be connected to the blockchain network or comprise a blockchain explorer with the required compatibility. In such a case, any third party verifier 450 may be able to query the blockchain network or a blockchain explorer connected to the blockchain network.

[0049] In some embodiments, the apparatus 100 may be configured to display upon query each verifiable credential 312-1; 312-2; 312-3; 312-n with its respective non-transf errable NFT 210-1; 210-2; 210-3; 210-n. The verifiable credentials 312-1; 312-2; 312-3; 312-n, which may include each of the respective digital addresses from which they came, may be provided with their respective cryptographic proofs for external verification.

[0050] In some embodiments, the third party verifier 450 may perform verification on the smart contract itself, e.g., through its source code. For example, for each instance of minting and issuing the non-transferable NFT 210, the smart contract may be pre-configured for ensuring that the verifiable credential 312 provided with the cryptographic proof 310 (of the first digital identity 200A) has not been used for previously minting another non-transferable NFT with reference to the same reference ID 330. Conversely, if one of the reference ID 330 or the verifiable credential 312 are different, then the minting and issuing of the non-transferable NFT may be allowed, assuming all other requirements are met. For example, a cryptographic accumulator stored on the blockchain and maintained by the smart contract can be used to store and scan all hash values used for minting and issuing previous non-transferable NFTs.

[0051] By examining the source code, the authenticity of the various non-transferable NFTs may also be verified. Furthermore, the cryptographic proof 310 using an acceptable structure (e.g., making use of a proper cryptographic hash function) also ensures that each digital identity can be verified for only one instance of minting and issuing a non-transferable NFT 210.

[0052] In Fig. 3, the feedback 320 is displayed in the form of the non-transferable NFT 210 itself. For example, the non-transferable NFT 210 may itself represent the feedback 320 as a form of authentic positive feedback or approval (e.g., a “like”, a thumbs up, etc.). In other embodiments, the non-transferable NFT 210 may represent an instance of authentic feedback that can be positive and / or negative to be displayed with more specific information. This may be in the form of a comment, a more specific rating, etc.

[0053] The embodiments presented above provide a scalable solution to efficient verification. Since verification of each instance of feedback is automated by means of cryptographic proofs, there is no need to perform their verification on an individual basis (i.e. repeating verification thousands of times for verifying feedback by thousands of users). Rather, the second digital identity 200B can demonstrate their authenticity of feedback much more efficiently, within the procedure itself.

[0054] In addition to demonstrating multiple instances of authenticated feedback, each from a respective user on the blockchain, the above-described methods may also enable demonstrating continued verification. In some embodiments, if a user wishes to withdraw or cancel the feedback 320, the non-transferable NFT 210 may be provided with an update. This is depicted in Figs. 4A and 4B.

[0055] In some embodiments, the non-transferrable NFT 210 may further comprise a status that is either active or inactive. Fig. 4A shows an active non-transferable NFT 210a being transformed to an inactive non-transferable NFT 210i. For example, the second digital identity 200B may have initially received the non-transferable NFT 210 reflecting the feedback of the first digital identity 200A, as depicted in Figs. 1 and 3. This may correspond to the active status 210a.

[0056] The first digital identity 200A may then have wished to cancel or withdraw the previous feedback and may submit further feedback 322A. Since the non-transferable NFT 210 reflecting the original feedback 320 may not be transferred and cannot be destroyed by any external identity, the non-transferable NFT 210 status, in some embodiments, may be changed by the first digital identity 200A from active (shown by 210a) to inactive (shown by 21 Oi). For each instance of changing the status, the further feedback 322A may be submitted with the cryptographic proof 310 including the verifiable credential 312, the reference ID 330, and the digital address 340 of the second digital identity 200B.

[0057] In some embodiments, depending on the wishes of the user (i.e. the first digital identity), the status may also be re-activated from inactive to active, as shown in Fig. 4B. In this case, the status may be switched from inactive to active, such as by receiving yet another round of feedback 322B by the first digital identity 200A regarding the published content. Just as for an previous instance, the smart contract may require that the cryptographic proof 310 (along with the reference ID 330 and the digital address 340) be sent with the verifiable credential 312 so that each instance is verified. In some embodiments, this may appear in the non-transferable NFT 210 as a withdrawn approval (e.g., a withdrawn thumbs up or a withdrawn like, etc.). In some embodiments, such as with a comment or rating, the comment or rating may have its contents displayed and shown as deactivated in favor of a new comment or rating to be shown as active.

[0058] To make such changes easy to implement, an appropriate user interface may be provided. For example, the published content may be visible while the user is logged into an online platform and the user interface may provide a means to provide the positive feedback (e.g., a thumbs up icon, a like-link, etc.). Furthermore, if the user later desires to withdraw the feedback, there may be a means available after submission of the initial feedback (e.g., a thumbs-down icon, an unlike-link, a withdraw “like” link, etc.).

[0059] Such features may be particularly useful for a configuration in which the non-transferrable NFTs 210 may not destroyed in any case, even by the holder of the NFT (i.e. the second digital identity 200B). By providing the features of an active or inactive non-transferrable NFT 210, all cases of feedback by each individual user (i.e. each case of the first digital identity 200A) are recorded over time and never deleted, allowing any third party to obtain an accurate impression of how the readers of the published content reacted. Based on patterns of how certain non-transferable NFTs were changed from active to inactive (or vice-versa), each third party may judge why such changes occurred and why the collective feedback up to the present point in time has occurred. The validity or value of the published content may then be judged more accurately with long-term transparency.

[0060] By providing either an active and inactive status for each non-transferable NFT 210, the verification is not only scalable and efficient, but also provides an even greater level of transparency for all interested parties. For published content that has achieved a greater level of publicity, long-term transparency may have particular importance. The embodiments described above enable all parties to see feedback trends over time, providing long-term transparency.

[0061] Fig- 5 shows a flowchart of an exemplary method 500 for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity. The method includes receiving a cryptographic proof 510 including a verifiable credential of the first digital identity, receiving feedback 520 of the first digital identity regarding the published content and a reference identification of the published content, and receiving a digital address 530 of the second digital identity. The method 500 further includes minting 540 a non-transferable non-fungible token, NFT, on a blockchain network. The non-transferable NFT comprises the verifiable credential of the first digital identity and the reference identification. Furthermore, the method 500 includes issuing 550 the non-transferable NFT to the digital address of the second digital identity.

[0062] The method may be performed by means of a smart contract on a blockchain network with the apparatus 100, as discussed in the embodiments of Figs. 1 to 4. In addition to such features, the smart contract may comprise pre-specified features for enabling the procedures presented above. This may include a struct (e.g., Struct LikeTokenlnfo), or a data structure grouping together variables of different datatypes under a single name. This can be used to define the structure of the non-transferable NFT 210, including a token ID, the digital address of the (respective) first digital identity 200A, the digital address 340 of the second digital identity 200B, the reference ID 330, and a status of whether the token is active or not.

[0063] Also, a proof verification function (e.g.. verifyproof) may be used to accept a succinct cryptographic proof including a hashed ID number, verify the proof, and return a Boolean indicating whether the proof is valid. If determined as valid, the minting may occur. For this a minting function (e.g., mintNTNFT) and / or an assigning function (e.g., assignNTNFT) may be used to allow the issuer to provide confirmation that the second digital identity 200B should receive the feedback and be assigned the non-transferable NFT 210. Such functions may be used to ensure that each non-transferable NFT 210 may be issued only once per combination of the digital identity 200A providing feedback specifically regarding the published content.

[0064] Furthermore, an updating status function (e.g., updateTokenStatus) may be used to enable the (respective) first digital identity 200A to update an active or inactive status of the non-transferable NFT 210. A validation mechanism may be used to ensure that only the (respective) first digital identity 200A can perform this action. For example, an active status may be set to true, which may express a “like”, while an inactive status may be set to false, which may express a withdrawn “like”. Other functions may serve to record such events related to changes in the smart contract (e.g., TokenMinled. TokenAssigned, TokenStatusUpdated, etc.) to facilitate tracking of significant interactions therein.

[0065] The following examples pertain to further embodiments:

[0066] (1) A method for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity, including: receiving a cryptographic proof including a verifiable credential of the first digital identity; receiving feedback of the first digital identity regarding the published content and a reference identification of the published content; receiving a digital address of the second digital identity; minting a non-transferable non-fun- gible token, NFT, on a blockchain network, wherein the non-transferable NFT comprises the verifiable credential of the first digital identity and the reference identification; and issuing the non-transferable NFT to the digital address of the second digital identity.

[0067] (2) The method of (1), wherein the non-transferable NFT is a SoulBound token.

[0068] (3) The method of (1) or (2), wherein the verifiable credential of the first digital identity is a cryptographic hash value of a government-issued identification number.

[0069] (4) The method of any one of (1) to (3), wherein the cryptographic proof is a zeroknowledge proof that is provided by the first digital identity. (5) The method of any one of (1) to (4), wherein the reference identification is a URL, an article ID, or a publication ID.

[0070] (6) The method of any one of (1) to (5), wherein the feedback regarding the published content comprises a vote, a rating, and / or a comment.

[0071] (7) The method of any one of (1) to (6), wherein the non-transferable NFT is minted on a condition that no other non-transferable NFT comprising both the verifiable credential of the first digital identity and the reference identification was previously minted on the blockchain.

[0072] (8) The method of any one of (1) to (7), wherein the non-transferable NFT further comprises a status that is either active or non-active, wherein the status may be switched from active to non-active or vice versa by receiving further feedback of the first digital identity regarding the published content in connection with a re-verification of the first digital identity.

[0073] (9) The method of any one of (1) to (8), wherein the method further includes minting a plurality of non-transferable NFTs, each corresponding to a respective digital identity, wherein each non-transferable NFT comprises the reference identification and a verifiable credential for the respective digital identity, issuing each of the plurality of non-transferable NFTs to the digital address of the second digital identity, and displaying upon query each of the plurality of non-transferable NFTs.

[0074] (10) The method of (9), wherein the method further includes displaying upon query each verifiable credential with its respective non-transferable NFT.

[0075] (11) A computer program having a program code for performing a method according to any one of (1) to (10) when the program is executed on a processor or a programmable hardware.

[0076] (12) A non-transitory machine-readable medium having stored thereon a program having a program code for performing the method according to any one of (1) to (10), when the program is executed on a processor or a programmable hardware. (13) An apparatus for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity, the apparatus comprising one or more interfaces for communication and processing circuitry configured to: receive a cryptographic proof including a verifiable credential of the first digital identity; receive feedback of the first digital identity regarding the published content and a reference identification of the published content; receive a digital address of the second digital identity; mint a non-transferable non-fungible token, NFT, comprising the verifiable credential of the first digital identity and the reference identification; and issue the non-transferable NFT to the digital address of the second digital identity.

[0077] The aspects and features described in relation to a particular one of the previous examples may also be combined with one or more of the further examples to replace an identical or similar feature of that further example or to additionally introduce the features into the further example.

[0078] Examples may further be or relate to a (computer) program including a program code to execute one or more of the above methods when the program is executed on a computer, processor or other programmable hardware component. Thus, steps, operations or processes of different ones of the methods described above may also be executed by programmed computers, processors or other programmable hardware components. Examples may also cover program storage devices, such as digital data storage media, which are machine-, processor- or computer- readable and encode and / or contain machine-executable, processor-executable or computerexecutable programs and instructions. Program storage devices may include or be digital storage devices, magnetic storage media such as magnetic disks and magnetic tapes, hard disk drives, or optically readable digital data storage media, for example. Other examples may also include computers, processors, control units, (field) programmable logic arrays ((F)PLAs), (field) programmable gate arrays ((F)PGAs), graphics processor units (GPU), application-specific integrated circuits (ASICs), integrated circuits (ICs) or system-on-a-chip (SoCs) systems programmed to execute the steps of the methods described above.

[0079] It is further understood that the disclosure of several steps, processes, operations or functions disclosed in the description or claims shall not be construed to imply that these operations are necessarily dependent on the order described, unless explicitly stated in the individual case or necessary for technical reasons. Therefore, the previous description does not limit the execution of several steps or functions to a certain order. Furthermore, in further examples, a single step, function, process or operation may include and / or be broken up into several sub-steps, - functions, -processes or -operations.

[0080] If some aspects have been described in relation to a device or system, these aspects should also be understood as a description of the corresponding method. For example, a block, device or functional aspect of the device or system may correspond to a feature, such as a method step, of the corresponding method. Accordingly, aspects described in relation to a method shall also be understood as a description of a corresponding block, a corresponding element, a property or a functional feature of a corresponding device or a corresponding system.

[0081] The following claims are hereby incorporated in the detailed description, wherein each claim may stand on its own as a separate example. It should also be noted that although in the claims a dependent claim refers to a particular combination with one or more other claims, other examples may also include a combination of the dependent claim with the subject matter of any other dependent or independent claim. Such combinations are hereby explicitly proposed, unless it is stated in the individual case that a particular combination is not intended. Furthermore, features of a claim should also be included for any other independent claim, even if that claim is not directly defined as dependent on that other independent claim.

Claims

Claims1. A method for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity, including: receiving a cryptographic proof including a verifiable credential of the first digital identity; receiving feedback of the first digital identity regarding the published content and a reference identification of the published content; receiving a digital address of the second digital identity; minting a non-transferable non-fungible token, NFT, on a blockchain network, wherein the non-transferable NFT comprises the verifiable credential of the first digital identity and the reference identification; and issuing the non-transferable NFT to the digital address of the second digital identity.

2. The method of claim 1, wherein the non-transferable NFT is a SoulBound token.

3. The method of claim 1, wherein the verifiable credential of the first digital identity is a cryptographic hash value of a government-issued identification number.

4. The method of claim 1 , wherein the cryptographic proof is a zero-knowledge proof that is provided by the first digital identity.

5. The method of claim 1, wherein the reference identification is a URL, an article ID, or a publication ID.

6. The method of claim 1, wherein the feedback regarding the published content comprises a vote, a rating, and / or a comment.

7. The method of claim 1, wherein the non-transferable NFT is minted on a condition that no other non-transferable NFT comprising both the verifiable credential of the first digital identity and the reference identification was previously minted on the blockchain.

8. The method of claim 1, wherein the non-transferable NFT further comprises a status that is either active or non-active, wherein the status may be switched from active to nonactive or vice versa by receiving further feedback of the first digital identity regarding the published content in connection with a re-verification of the first digital identity.

9. The method of claim 1, wherein the method further includes minting a plurality of non-transferable NFTs, each corresponding to a respective digital identity, wherein each non-transferable NFT comprises the reference identification and a verifiable credential for the respective digital identity, issuing each of the plurality of non-transferable NFTs to the digital address of the second digital identity, and displaying upon query each of the plurality of non-transferable NFTs.

10. The method of claim 9, wherein the method further includes displaying upon query each verifiable credential with its respective non-transferable NFT.

11. A computer program having a program code for performing a method according to claim 1 when the program is executed on a processor or a programmable hardware.

12. A non-transitory machine-readable medium having stored thereon a program having a program code for performing the method of claim 1, when the program is executed on a processor or a programmable hardware.

13. An apparatus for obtaining authenticated feedback from a first digital identity regarding published content of a second digital identity, the apparatus comprising: one or more interfaces for communication; and processing circuitry configured to: receive a cryptographic proof including a verifiable credential of the first digital identity; receive feedback of the first digital identity regarding the published content and a reference identification of the published content;receive a digital address of the second digital identity; mint a non-transferable non-fungible token, NFT, comprising the verifiable credential of the first digital identity and the reference identification; and issue the non-transferable NFT to the digital address of the second digital identity.

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