Chapter 1
Introduction
God had meant photons to travel rather than to stay put! This
was the insight that made us think of using a quantum channel to
transmit confidential information. Gilles Brassard
Quantum cryptography exploits distinctive quantum properties of nature in order to
perform a given cryptographic task. Most quantum cryptographic protocols are—at
least in principle—information-theoretically secure, which is a very strong notion of
security as it is deduced purely from information theory.
Early ideas to use quantum properties for security purposes date back to the 70’s
[1, 2], when Wiesner aimed to create unfalsifiable bank notes [3]. These ideas seemed
however very unpractical as they required to store a single polarized photon for days
without losses (at the time, photon polarization was the only conceived carrier of
quantum information).
The breakthrough occurred in 1983, when Bennett and Brassard realized that photons are best used to transmit quantum information rather than to store it. In particular,
they could be used to transmit a random secret key from a sender to a receiver, who
can then use the key to encrypt and decrypt sensitive messages. Shortly after, Bennett
and Brassard published the first quantum key distribution (QKD) protocol in 1984
[4], hence named BB84 protocol. A QKD protocol enables two parties to generate
a shared secret key via an insecure quantum channel and an authenticated public
classical channel. Since then, many new protocols have been proposed [5–7] and
implemented [8], allowing QKD to become the flagship of quantum cryptography
and one of the major applications of quantum information science.
Furthermore, pushed by increasing concerns on data security and by the prospect
of commercialization, the research on quantum cryptography has spread beyond the
walls of academia and attracted the attention of several companies, private institutions
and governments [9, 10]. In fact, a growing number of companies and start-ups
worldwide are offering quantum cryptographic solutions.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
F. Grasselli, Quantum Cryptography, Quantum Science and Technology,
https://doi.org/10.1007/978-3-030-64360-7_1
1
Introduction
God had meant photons to travel rather than to stay put! This
was the insight that made us think of using a quantum channel to
transmit confidential information. Gilles Brassard
Quantum cryptography exploits distinctive quantum properties of nature in order to
perform a given cryptographic task. Most quantum cryptographic protocols are—at
least in principle—information-theoretically secure, which is a very strong notion of
security as it is deduced purely from information theory.
Early ideas to use quantum properties for security purposes date back to the 70’s
[1, 2], when Wiesner aimed to create unfalsifiable bank notes [3]. These ideas seemed
however very unpractical as they required to store a single polarized photon for days
without losses (at the time, photon polarization was the only conceived carrier of
quantum information).
The breakthrough occurred in 1983, when Bennett and Brassard realized that photons are best used to transmit quantum information rather than to store it. In particular,
they could be used to transmit a random secret key from a sender to a receiver, who
can then use the key to encrypt and decrypt sensitive messages. Shortly after, Bennett
and Brassard published the first quantum key distribution (QKD) protocol in 1984
[4], hence named BB84 protocol. A QKD protocol enables two parties to generate
a shared secret key via an insecure quantum channel and an authenticated public
classical channel. Since then, many new protocols have been proposed [5–7] and
implemented [8], allowing QKD to become the flagship of quantum cryptography
and one of the major applications of quantum information science.
Furthermore, pushed by increasing concerns on data security and by the prospect
of commercialization, the research on quantum cryptography has spread beyond the
walls of academia and attracted the attention of several companies, private institutions
and governments [9, 10]. In fact, a growing number of companies and start-ups
worldwide are offering quantum cryptographic solutions.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
F. Grasselli, Quantum Cryptography, Quantum Science and Technology,
https://doi.org/10.1007/978-3-030-64360-7_1
1