CryptiQ

People are getting more and more concerned about long-term privacy and confidentiality of personal digitalized data exchanged over the Internet. Furthermore, there has recently been a substantial amount of research on quantum computers, which offer considerably greater computational power than their classical counterparts. The NIST's intent to standardize post-quantum cryptographic protocols reveals the need to be prepared to a quantum attacker which could completely break many widely-used public-key cryptosystems. On the positive side, although a universal quantum computer powerful enough to lead such attacks may be some decades in the future, quantum communication technologies are becoming concretely available in practice and it is already possible to prepare, manipulate and precisely control systems involving a few quantum information bits (qubits). Such technologies can be used to quantum-enhance classical protocols and help improve their efficiency or security in a number of ways. The goal of the CryptiQ project is to anticipate these major changes by considering three plausible scenarios, from the closest to the furthest foreseeable future, depending on the means of the adversary and the honest parties. In the first scenario, the honest execution of protocols remains classical while the adversary may have oracle access to a quantum computer. This is the so-called post-quantum cryptography, which is the best known setting. In the second scenario (quantum-enhanced classical cryptography), we allow honest parties to have access to quantum technologies in order to achieve enhanced properties, but we restrict this access to those quantum technologies that are currently available (or that can be built in near-term). The adversary is still allowed to use any quantum technology. Finally, in the third scenario (cryptography in a quantum world), we allow the most general quantum operations to an adversary and we consider that anybody can now have access to both quantum communication and computation. In each case, we plan to find the most relevant adversarial and security models and to give a formal security proof of each protocol that we will design. Such study will need the joint work of both classical cryptographers and quantum computer scientists, as suggested by the team proposed in the CryptiQ project.