CloudStash: Using Secret-Sharing Scheme to Secure Data, Not Keys, in Multi-clouds

Cloud storages have many exciting features that attract many individuals and organizations for storing and sharing data over the cloud. However, security and key management are still remaining the highlighted concerns in cloud storage. Managing/protecting keys is a problem for existing approaches, and opens the risk of attackers working to offline brute-force crack the decryption and/or surreptitiously obtaining the key and using it offline. To address these issues, we propose the Cloud Stash scheme, a system that applied the secret-sharing scheme directly on the file to store multi-shares of a file into multi-clouds. Cloud Stash utilizes secret-sharing, low cost cloud storages and multi-threading to improve confidentiality, availability, performance and fault tolerance. Cloud Stash achieves this improvement by splitting a file into multi-shares of secret and distributing these multi-shares into multi-clouds simultaneously where threshold shares are required to reconstruct the file. Our experiments show that Cloud Stash is statistically significantly faster for small files, and even for large files the added cost is not statistically worse. So the added security benefits are nearly free from the users' perspective.