Cryptography in a Quantum World – 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.