The integration of business processes across organizations is typically beneficial for all involved parties. However, the lack of trust is often a roadblock. Blockchain is an emerging technology for decentralized and transactional data sharing across a network of untrusted participants. It can be used to find agreement about the shared state of collaborating parties without trusting a central a...

One of the most impactful applications of proofs of work (POW) currently is in the design of blockchain protocols such as Bitcoin. Yet, despite the wide recognition of POWs as the fundamental cryptographic tool in this context, there is no known cryptographic formulation that implies the security of the Bitcoin blockchain protocol. Indeed, all previous works formally arguing the security of the...

Since the inception of Bitcoin technology, its underlying data structureâĂŞ-the blockchainâĂŞ-has garnered much attention due to properties such as decentralization, transparency, and immutability. These properties make blockchains suitable for apps that require disintermediation through trustless exchange, consistent and incorruptible transaction records, and operational models beyond cryptocu...

Blockchain technology alleviates the reliance on a centralized authority to certify information integrity and ownership, as well as mediate transactions and exchange of digital assets, while enabling secure and pseudo-anonymous transactions along with agreements directly between interacting parties. It possesses key properties, such as immutability, decentralization, and transparency, that pote...

Bitcoin is the first implementation of what has become known as a ‘public permissionless’ blockchain. Guaranteeing security and protocol conformity through its elegant combination of cryptographic assurances and game theoretic economic incentives, it permits censorship resistant public read-write access to its append-only blockchain database without the need for any mediating central authority....

We design and implement the first private and anonymous decentralized crowdsourcing system ZebraLancer. It realizes the fair exchange (i.e. security against malicious workers and dishonest requesters) without using any third-party arbiter. More importantly, it overcomes two fundamental challenges of decentralization, i.e. (i) data leakage and (ii) identity breach. First, our outsource-then-prov...

We design and implement TwinsCoin, the €rst cryptocurrency based on a provably secure and scalable public blockchain design using both proof-of-work and proof-of-stake mechanisms. Di‚erent from the proof-ofwork based Bitcoin, our construction uses two types of resources, computing power and coins (i.e., stake). Œe blockchain in our system is more robust than that in a pure proof-of-work based s...

Nakamoto’s famous blockchain protocol enables achieving consensus in a so-called permissionless setting—anyone can join (or leave) the protocol execution, and the protocol instructions do not depend on the identities of the players. His ingenious protocol prevents “sybil attacks” (where an adversary spawns any number of new players) by relying on computational puzzles (a.k.a. “moderately hard f...

Generally scarce computational and memory resource availability is a well known problem for the IoT, whose intrinsic volatility makes complex applications unfeasible. Noteworthy efforts in overcoming unpredictability (particularly in case of large dimensions) are the ones integrating Knowledge Representation technologies to build the so-called Semantic Web of Things (SWoT). In spite of allowed ...

Blockchain technologies offer new open sourcebased opportunities for developing new types of digital platforms and services. While research on the topic is emerging, it has this far been predominantly focused to technical and legal issues. To broaden our understanding of blockchain technology based services and platforms, we build on earlier literature on payments and payment platforms and prop...