A new quantum oracle model for a hybrid quantum-classical attack on post-quantum lattice-based cryptosystems

Lattice-based cryptosystems are one of the main post-quantum alternatives to asymmetric cryptography currently in use. Most attacks on these cryptosystems can be reduced to the shortest vector problem (SVP) in a lattice. Previously, the authors proposed a quantum oracle model from Grover’s algorithm to implement a hybrid quantum-classical algorithm based on the GaussSieve algorithm and solving SVP. In this paper, a new model of a quantum oracle is proposed and analyzed. Two implementations of the new quantum oracle model are proposed and estimated. The complexity of implementing the new quantum oracle model to attack post-quantum lattice-based cryptosystems that are finalists of the NIST post-quantum cryptography competition is analyzed. Comparison of obtained results for new and existing models of quantum oracle is given. Tab. 4, illustr. 10, bibliogr. 48.