Quantum Random Oracle Model for Quantum Public-Key Encryption

Random oracle model is a general security analysis tool for rigorous security proof and effective cryptographic protocol design. In the quantum world, the attempts of constructing a quantum random oracle (QRO) have been made, such as quantum-accessible random oracle for post-quantum cryptography and quantum random oracle for quantum digital signature. As in the classical circumstance, it is crucial and challenging to design and instantiate the QRO model with an appropriate quantum hash function. In this work, we construct a QRO model for quantum public-key encryption against key-collision attack, due to the near-orthogonality property of the QRO. To explore a feasible instantiation procedure in the quantum setting, we distinctively give two instantiation examples of QRO by means of single-qubit rotation and quantum fingerprinting, and compare the numerical results of their performances under the key-collision attack. As a result, we extend the QRO model to the security analysis of quantum public-key encryption beyond quantum digital signature, and immunity from collision-type attacks.