Post-Quantum Security of the Fujisaki-Okamoto and OAEP Transforms.

In this paper, we present a hybrid encryption scheme that is chosen ciphertext secure in the quantum random oracle model. Our scheme is a combination of an asymmetric and a symmetric encryption scheme that are secure in a weak sense. It is a slight modification of the Fujisaki-Okamoto transform that is secure against classical adversaries. In addition, we modify the OAEP-cryptosystem and prove its security in the quantum random oracle model based on the existence of a partial-domain one-way injective function secure against quantum adversaries.