Toward protecting control flow confidentiality in cloud-based computation

Idea: • Transform each original program into a public program and a private program. • Public program: execute on the public cloud; perform most execution except for evaluating predicates of branch statements. • Private program: execute on private cloud; evaluate predicates. Proposed Techniques: • Replace predicates of the branch statements in the original program with control flow query (CFQ) invocations to the private program. • Insert indistinguishable fake branch statements in the original program to raise the bar for the attacker to understand the algorithm’s control flow. • Maintain a continuous cache to reduce the cost of cross-cloud communication.