Description

Despite the tremendous benefits, outsourcing computation also inevitably suffers from some new security challenges [42], [50]. Firstly, the computation tasks often contain some sensitive information that should not be exposed to the (semi-trusted) cloud servers. Therefore, the first security challenge is the privacy of the outsourcing computation: the curious cloud servers should not learn anything about what it is actually computing (including the secret inputs and outputs). We argue that the traditional encryption technique can only provide a partial solution to this problem since it is very difficult to perform meaningful computations over the ciphertext.Though the fully homomorphic encryption could be a potential solution, the existing schemes are not practical yet. Secondly, the semi-trusted cloud servers may return an invalid result. For example, the servers might contain a software bug that will fail on a constant number of invocation. Moreover, the servers might decrease the amount of the computation due to financial incentives and then return a computationally indistinguishable (invalid) result. Therefore, the second security challenge is the checkability of the outsourcing computation: the outsourcer should have the ability to detect any failures if the cloud servers misbehave. Trivially, the test procedure should never be involved in some other complicated computations since the computationally limited devices may be incapable to accomplish a complicated test. At the very least, it must be far more efficient than accomplishing the computation task itself (recall the motivation for outsourcing computations).