there are many security and privacy challenges impeding the wide adoption of cloud computing in
the healthcare domain. In this paper, we presented a novel
architecture for inter-organizational data sharing and its
implementation, which provides a high level of security and
privacy for patient data in semi-trusted cloud computing
environments. This architecture features attribute-based
encryption for selectively authorizing access to data and
cryptographic secret-sharing in order to securely distribute
data across multiple clouds, reducing the adversarial capabilities of curious cloud providers. Our implementation
and evaluation by several experiments indicated the practical feasibility and good performance. Future work will
address inter-organizational aspects of key management
and RBAC policy management, usability studies, and several
enhancements for the Multi-Cloud Proxy.