Secure Keyless Multi-party Storage Scheme

Using threshold secret sharing, we propose a solution tailored for forgetful clients (i.e., not required to keep any cryptographic secret) while accommodating the dynamic nature of multi-cloud deployments. Furthermore, we delegate the computation and distribution of shares to an intermediate server (proxy), effectively minimizing the client workload. We propose two variants of a keyless, space-efficient multi-cloud storage scheme named KAPRE and KAME. Our solution KAPRE requires less communications and computations, while KAME preserves data confidentiality against a colluding proxy. Our protocols offer robust guarantees for data integrity, and we demonstrate the proxy's ability to identify and attribute blame to servers responsible for sending corrupted shares during data reconstruction. We establish a comprehensive security model and provide proofs of the security properties of our protocols. To complement this theoretical analysis, we present a proof-of-concept to illustrate the practical implementation of our proposed scheme.