Chapter 3
Introducing Quantum Key Distribution
As the need for unbreakable encryption looms in networks
around the world, quantum cryptography is the solution that will
safeguard and future-proof sensitive information. Commercial
QKD company
Abstract Quantum key distribution (QKD) is arguably the most developed task of
quantum cryptography, both from a theoretical and experimental point of view. In
this Chapter we first present some of the security principles of QKD in Sect. 3.1.
We then describe the BB84 protocol as an example of QKD protocol and compute
its key rate (Sect. 3.2). Section 3.3 is bit more technical, here we define and prove
the security of a generic QKD protocol in the finite-key scenario. We conclude the
Chapter by providing an incomplete overview of the most recent state-of-the-art
QKD experiments (Sect. 3.4). In the Appendix (Sects. 3.5 and 3.6) we report the
details of some proofs of the main text.
The security of classical cryptographic schemes relies on assumptions on the adversary’s computational capabilities and on the fact that certain mathematical problems
are considered “hard” to solve. This makes classical cryptography vulnerable to
retroactive attacks. That is, an adversary could store the encrypted data while it is
communicated and wait to have sufficient computational power, or smarter algorithms, in order to decrypt it. Conversely, the security of quantum cryptography
relies on intrinsic principles of nature, as described by quantum mechanics. Therefore, assuming that quantum mechanics is correct, the security offered by quantum
cryptography is everlasting, in the sense that it is independent of future theoretical
or experimental advances of the adversary.
© 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_3
35
Introducing Quantum Key Distribution
As the need for unbreakable encryption looms in networks
around the world, quantum cryptography is the solution that will
safeguard and future-proof sensitive information. Commercial
QKD company
Abstract Quantum key distribution (QKD) is arguably the most developed task of
quantum cryptography, both from a theoretical and experimental point of view. In
this Chapter we first present some of the security principles of QKD in Sect. 3.1.
We then describe the BB84 protocol as an example of QKD protocol and compute
its key rate (Sect. 3.2). Section 3.3 is bit more technical, here we define and prove
the security of a generic QKD protocol in the finite-key scenario. We conclude the
Chapter by providing an incomplete overview of the most recent state-of-the-art
QKD experiments (Sect. 3.4). In the Appendix (Sects. 3.5 and 3.6) we report the
details of some proofs of the main text.
The security of classical cryptographic schemes relies on assumptions on the adversary’s computational capabilities and on the fact that certain mathematical problems
are considered “hard” to solve. This makes classical cryptography vulnerable to
retroactive attacks. That is, an adversary could store the encrypted data while it is
communicated and wait to have sufficient computational power, or smarter algorithms, in order to decrypt it. Conversely, the security of quantum cryptography
relies on intrinsic principles of nature, as described by quantum mechanics. Therefore, assuming that quantum mechanics is correct, the security offered by quantum
cryptography is everlasting, in the sense that it is independent of future theoretical
or experimental advances of the adversary.
© 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_3
35