An Unconditionally Secure and Non-malleable Encryption Scheme for Cloud Storage

We consider a system consisting of a user and a public cloud storage provider. We provide an unconditionally secure and non-malleable encryption scheme for storing the confidential data of the user on the public cloud storage. More specifically, we show that the proposed scheme provides: i) semantic security against an all-powerful adversary, i.e., with unbounded computational power who has complete access to the communication line, and ii) ciphertext integrity against the all-powerful adversary. To provide the scheme, we use the Encrypt-then-MAC approach, and it is implemented by exploiting finite group modular addition. As an illustrative example, according to the proposed scheme, by using around 46.4 Terabytes (TBs) of secret bits, a user can store around 1.96 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> TBs of data on public storage with guaranteed everlasting security.