Light blind: Why encrypt if you can share?

The emergence of cloud computing makes the use of remote storage more and more common. Clouds provide cheap and virtually unlimited storage capacity. Moreover, thanks to replication, clouds offer high availability of stored data. The use of public clouds storage make data confidentiality more critical as the user has no control on the physical storage device nor on the communication channel. The common solution is to ensure data confidentiality by encryption. Encryption gives strong confidentiality guarantees but comes with a price. The time needed to encrypt and decrypt data increases with respect to the size of input data, making encryption expensive. Due to its overhead, encryption is not universally used and a non-negligible amount of data is insecurely stored in the cloud. In this paper, we propose a new mechanism, called Light Blind, that allows confidentiality of data stored in the cloud at a lower time overhead than classical cryptographic techniques. The key idea of our work is to partition unencrypted data across multiple clouds in such a way that none of them can reconstruct the original information. In this paper we describe this new approach and we propose a partition algorithm with constant time complexity tailored for modern multi/many-core architectures.