Cryptocurrencies like Bitcoin have proven to be a phenomenal success. Bitcoin-like systems use proofof-work mechanism which is therefore considered as 1-hop blockchain, and their security holds if the majority of the computing power is under the control of honest players. However, this assumption has been seriously challenged recently and Bitcoin-like systems will fail when this assumption is b...

In the setting of blockchain based transaction ledgers we study the problem of “simplified payment verification” (SPV) which refers to the setting of a transaction verifier that wishes to examine the last k blocks of the blockchain (e.g., for the purpose of verification of a certain transaction) using as only advice the genesis block (or some “checkpoint” block that is known to it). The straigh...

We examine blockchain technologies, especially smart contracts, as a platform for decentralized applications. By providing a basis for consensus, blockchain promises to upend business models that presuppose a central authority. However, blockchain suffers from major shortcomings arising from an over-regimented way of organizing computation that limits its prospects. We propose a sociotechnical,...

Large-scale transactional systems still suffer from not viable trust management strategies. Given its intrinsic characteristics, blockchain technology appears as interesting from this perspective. A semantic layer built upon a basic blockchain infrastructure would join the benefits of flexible resource/service discovery and validation by consensus. This paper proposes a novel Service-oriented A...

We present an identity management scheme built into the Bitcoin blockchain, allowing for identities that are as indelible as the blockchain itself. Moreover, we take advantage of Bitcoin’s decentralized nature to facilitate a shared control between users and identity providers, allowing users to directly manage their own identities, fluidly coordinating identities from different providers, even...

Data is nowadays an invaluable resource, indeed it guides all business decisions in most of the computer-aided human activities. Threats to data integrity are thus of paramount relevance, as tampering with data may maliciously affect crucial business decisions. This issue is especially true in cloud computing environments, where data owners cannot control fundamental data aspects, like the phys...

This report documents the program and the outcomes of Dagstuhl Seminar 17132 “Opportunities and Risks of Blockchain Technologies”. Blockchain-based applications such as Bitcoin or Ethereum are emerging technologies, but a dramatic increase in industrial and academic interest in the technology is evident. Start-ups and large financial players are working intensely on blockchain-based application...

This paper looks at the challenges and opportunities of implementing blockchain technology across banking, providing food for thought about the potentialities of this disruptive technology. The blockchain technology can optimize the global financial infrastructure, achieving sustainable development, using more efficient systems than at present. In fact, many banks are currently focusing on bloc...

We propose a proof-of-work algorithm that rewards blockchain miners for using computational resources to solve NP-complete puzzles. The resulting blockchain will publicly store and improve solutions to problems with real world applications while maintaining a secure and fully functional transaction ledger.

Blockchain technology and distributed ledgers are attracting massive attention and trigger multiple projects in different industries. However, the financial industry is seen as a primary user of the blockchain concept. This is not only due to the fact that the most well-known application of this technology is the crypto-currency Bitcoin, but it is also driven by substantial process inefficienci...