SklCoin: Toward a Scalable Proof-of-Stake and Collective Signature Based Consensus Protocol for Strong Consistency in Blockchain

The proof-of-work consensus protocol suffers from two main limitations: waste of energy and offering only probabilistic guarantees about the status of the blockchain. This paper introduces SklCoin, a new Byzantine consensus protocol and its corresponding software architecture. This protocol leverages two ideas: 1) the proof-of-stake concept to dynamically form stake proportionate consensus groups that represent block miners (stakeholders), and 2) scalable collective signing to efficiently commit transactions irreversibly. SklCoin has immediate finality characteristic where all miners instantly agree on the validity of blocks. In addition, SklCoin supports high transaction rate because of its fast miner election mechanis

Leveraging Distributed Ledger Technology for Decentralized Mobility-as-a-Service Ticket Systems

Mobility-as-a-Service (MaaS) is a concept for combining different transport modes, including diverse mobility services, while facilitating their use through customer centricity (e.g., pay-as-you-go tariffs, unified interfaces). MaaS platforms offer access to different mobility services of various providers via MaaS ticket systems. IT governance of current ticket systems is largely assigned to central organizations that guide decisions on the ticket system design, modalities, and the participation of mobility providers. Mobility providers depend on decisions of system providers, which can cause discrimination of competitors in MaaS ticket systems and limit flexibility for customers. By distributing decision rights to multiple mobility providers, IT governance for MaaS ticket systems can be decentralized so that dependencies on single providers are reduced. Distributed Ledger Technology (DLT) can be suitable to technically support such decentralization. However, DLT causes new challenges (e.g., regarding confidentiality, cost, latency, and maintainability), which question the viable use of DLT in real-world deployments of MaaS ticket systems. We present a preliminary sociotechnical model of a decentralized ticket system, point out technical challenges for using DLT in decentralized ticket systems based on common requirements for MaaS platforms, and describe exemplary solutions to address these challenges. Thereby, we contribute to a better understanding about the viable use of DLT in MaaS ticket systems. Our results indicate that the use of Trusted Execution Environments (TEEs) is especially promising to increase performance and confidentiality. We outline future research directions regarding the applicability of TEEs in real-world MaaS ticket systems