Public key authenticated encryption with keyword search: revisited

In 2017, the notion of public key authenticated encryption with keyword search (PAEKS) and its security model was defined by Huang and Li. Their main motivation was providing security against inside keyword guessing attacks (KGA). They also proposed a concrete PAEKS scheme secure in their proposed model. In this study, the authors first show that their security model has an important drawback and therefore, cannot handle multi-user settings. As such settings are a necessity in the public-key environment, it is vital to improving the model to capture multiple users. This is what they do in the first part of this study. Then, they consider Huang and Li's PAEKS scheme and prove that it is not secure against inside (and even outside) KGA. Finally, they propose a modified scheme to fix the problem without any additional communication or computation costs. They further prove that the new scheme is secure in the improved model.