# ID-Service: A Blockchain-Based Platform to Support Digital-Identity-Aware Service Accountability
## 1 Introduction  
In today's business, globalization has leading new markets and opportunities and, at the same time, the need to address rapidly changing market conditions in a more flexible and effective way than ever before. To this aim, the emerging business model adopted by organizations is to focus on their competitive advantage, performing only those functions for which they have expert skills and they complement their offering through partners and suppliers. In this context, Cross-Organizational Workflows (COWs) [1, 2, 3] came into play. However, the design and management of this kind of workflows are more difficult than traditional ones, also because the participation of possibly conflicting parties enforces higher levels of assurance about security and trustworthiness features. This is complicated by the intrinsic lack of global workflow schemes (managed by the engine of the system) and central coordinating bodies, due to the decentralized nature of COWs. One of the features that may provide digital services with a competitive advantage is certainly accountability. A service is accountable if trusted mechanisms are enabled to trace actions and link them in a secure way with the involved actors, in such a way that responsibility can be claimed with an appropriate level of assurance, and, thus, actions cannot be repudiated or falsely attributed. Obviously, accountability is strictly related to reliable identity management. No responsibility can be claimed if the involved digital entities are not securely linked to reliable digital identities. The other need is the ability to trace workflows at least in the sensitive points (e.g., inter-organization actions) in a way that integrity and authenticity are securely preserved. The approach followed in our project to attribute certain identity to the critical actors of services is to rely on a Public Digital Identity Systems compliant with the EU regulation eIDAS [4]. It is worth noting that the trusted third parties required by the eIDAS ecosystem (i.e., the Identity Providers) are definitely not in conflict with the distributed nature of COWs because they can be view as orthogonal entities provided _for free_ in real-life contexts (at least in the European Union). Instead, to accomplish accountability, without involving in the COWs dedicated central TTPs, we leverage the Blockchain technology as a platform for both secure tracing and trusted execution. Blockchain has proved to lend itself well to the implementation of cooperative processes that involve different organizations [5; 6; 7], because:  
1. Blockchain enables these processes to be executed in a distributed manner without delegating trust to central authorities nor requiring mutual trust between each pair of parties. 2. Blockchain can serve as an immutable public register in which to store the history of the interactions, structured as a feedback control mechanism of information exchange between a sender and a receiver, at a certain point in time, providing a clear and openly verifiable indication of unexpected behaviours. 3. The logic of interaction of COWs could be codified within smart contracts ensuring the correct execution of the shared process. Smart contracts are a further element of control of the process execution, as they only accept coded interactions and only if executed by the participants who have the necessary authorizations. Unfortunately, no native mechanism in Blockchain exists to manage securely the identity of the involved actors. Although the use of the blockchain in the implementation of organizational processes is currently a growing trend, as shown by the various applications and experiments in the field of academic and industrial research, there are still critical issues for which efficient and robust solutions must be found. One of them concerns the certification of the identity of the participants in the process, which is referred to by the term _accountability_.