Cryptography in a Quantum World

The Eduard Rhein Technology Award is presented annually for outstanding contributions to information technologies. In 2023, the recipients are Prof. Gilles Brassard and Charles H. Bennett, and they will present their findings in a special colloquium.

Is the fact that we live in a quantum world a curse or a blessing for cryptography?

Prof. Gilles Brassard, Ph. D. | Université de Montréal and Senior Fellow, Institute for Theoretical Studies, ETH Zürich

Recent theoretical and practical developments of quantum cryptography

Charles H. Bennett, Ph. D. | Research Staff & IBM Fellow, IBM Research Division and Foreign Member of the Royal Society of London

Abstract

Gilles Brassard will discuss how quantum theory opens up new vistas both for codebreakers and codemakers, with an emphasis on the latter. Charles H. Bennett will discuss recent developments such as deviceindependent and measurement-device independent quantum cryptography, and how quantum theory illuminates the notion of privacy.

Public key cryptography opened an approach with everyone being able to encrypt a message using a recipient’s public key. Only the recipient, who knows the corresponding secret key, would be able to decrypt it. So there would be two keys , one for encryption, which is public, and one for decryption, which is kept secret by its owner. The public key cryptosystems most widely used today are RSA, Diffie-Hellman, and elliptic curves.

At the present, these schemes enable our digital society. They rely on the expected complexity of inverting the encryption function without knowledge of the secret key. In the long term these schemes are threatened by future capabilities of quantum computers. The conception of the first quantum key distribution (QKD) protocol by Bennett and Brassard – this year’s recipients of the Eduard Rhein Technology Award – stands out in this respect. Their scheme is secure due to specific properties of quantum mechanics rather than due to an expected computational complexity. Quantum mechanics is one of the best-established physical theories. If it holds and if the scheme is implemented correctly, QKD is provably secure. This is a qualitative difference – there is no classical equivalence.

For more information, please visit www.eduard-rhein-stiftung.de