Jacob Eberhardt's research while affiliated with Technische Universität Berlin and other places

... Nevertheless, blockchain technologies continue adopting new techniques to address rising transaction costs, scalability limits, and performance issues of execution engines, respectively [20]- [22]; Especially since hype-driven blockchain applications (e.g., Cryptokitties or ICOs) caused fees to skyrocket [23] multiple times, in the past. The constantly increasing block size limit in Ethereum also suggests that the overall demand will continuously increase. ...

... DApps therefore depend on reliably distinguishing the users by some kind of distinct attributes that only a single participant or a group of users possesses and for which a proof can be provided. In decentralized finance (DeFi) lending DApps [30], for instance, lenders and borrowers may be required to prove possession of a valid citizenship or tax number, in IoT DApps [25], devices may have to prove official calibration or certain configuration parameters, and participants of marketplaces [20] may be required to prove creditworthiness before they are allowed to engage into trading. The attestation of such attributes can come from different issuers such as tax offices, calibration authorities, or credit bureaus. ...

... Heiss et al. focused on detecting consent violations in a publicly verifiable way and reporting them (Heiss et al., 2020). Their smart contract based solution was designed to support service providers to fulfil three particular obligations: establishing an auditable archive of consent policies, providing an appropriate technical measure to ensure and to be able to demonstrate the legally valid processing of personally identifiable information, and finally reporting of consent violations to the supervisory authority. ...

... Blockchain technology is increasingly used in the Internet of Things (IoT) to store and process critical sensor data originating from and shared between multiple, often mutually distrusting parties [20,24,15,16,7,12,23]. In local energy grids with blockchain-based energy trading, for example, energy consumers and producers depend on smart meter-generated measurement data [19,7]. ...

... On the other hand, Relays are a piece of software hosted on the target chain that verifies the information received from the source chain according to the rules defined in the source chain's consensus protocol. This verification can be made using an SPV [1] or more sophisticated proofs like Zk-SNARKSs [49] or NiPoPoW [94]. Sidechains follow a three layer architecture, where layer 0 is the ledger, layer 1 is the blockchain platform on top of the ledger, and layer 2 is the sidechain. ...

... Yet, to perform its task, the proposed scheme covers components in both the on-chain and off-chain world. For these reasons, we have opted for the oracle concept [33] as an alternative to request identity data from external parties. As a matter of fact, to interact with outside sources (IdPs and SPs) during Attribute Aggregation and the membership process, the suggested paradigm relies on a pool of oracles that fetch data from the outside world onto the federated Blockchain. ...

... Additionally, we develop requester and worker Java applications that connect with the Rinkeby [6] and Goerli [3] test networks using the Web3j framework. We use the Zokrates toolbox [18] for all zk-SNARKs implementation. Last, we perform all cryptographic operations over the ALT_BN128 elliptic curve [57]. ...

... To define an appropriate solution (i.e., fulfilling the SDPs' objectives while considering the forces), we went back to the data gathered through identifying and synthesizing challenges and solutions and compared proposed solutions for a given challenge. For example, prior research proposes using the Oracle Pattern whenever external data or realworld data is required by a smart contract [70], [71]. We synthesized information about oracles to come up with a solution for our SDP. ...

... Recently, several types of research have been employed in creating blockchain-based marketplace systems for diverse specialties such as circular economy [6], [7], energy [8,9], IoT data [10,11], computer resources [12], and art [13]. For example, Klems et al. presented decentralized service marketplaces that leverage smart contracts to eliminate the need for trust in marketplace intermediaries and lower entry barriers, lock-in, and transaction costs [14]. However, all the above works provide a secure platform for virtual products, such as books, songs, art, and data. ...

... ZKP methods meet the requirements for privacy and keep the essential characteristics of blockchain: the absence of a trusted third party (TTP) and the traceability of data. ZKP is characterized by the following properties [7]: ...