Quantum-assisted digital signature: a new service for future quantum-integrated optical networks

One of the most important applications of cryptography is digital signature (DS), which aims to certify the provenance of a message as well as its authenticity, ensuring the nonrepudiation, unforgeability, and transferability of messages. However, the forthcoming advent of quantum computers poses a significant threat to classical signature schemes. In this work, an improved version of a novel quantum-assisted digital signature (QADS) solution will be presented, in which quantum keys generated by quantum key distribution (QKD) are used together with standard classical cryptographic functions to provide a hybrid system that integrates quantum and classical cryptography. The quantum keys enhance the security of the DS, allowing to sign messages with arbitrary lengths while maintaining a suitable DS length. The proposed solution could push the practical exploitation of QKD in a new application domain, leading to a more pervasive integration of quantum technology in realistic scenarios.