Identity-Based Encryption Secure Against Selective Opening Attack
The authors present the first Identity-Based Encryption (IBE) schemes that are proven secure against Selective Opening Attack (SOA). This means that if an adversary, given a vector of ciphertexts, adaptively corrupts some fraction of the senders, exposing not only their messages but also their coins, the privacy of the unopened messages is guaranteed. Achieving security against such attacks is well-known to be challenging and was only recently solved in the PKE case, but the techniques used there do not solve the IBE case. The solutions illustrate two techniques to achieving SOA-secure IBE, one based on the Boyen-Waters anonymous IBE and the other based on Waters' dual-system approach.