Cryptographic security of quantum key distribution
This work provides foundational insights for ensuring QKD remains secure when integrated into broader cryptographic systems, addressing a critical need for quantum communication security.
The paper tackles the problem of defining cryptographic security for Quantum Key Distribution (QKD) by reviewing necessary security notions for protocol composition and deriving a corresponding security criterion, with examples showing that composed protocol errors sum to those of individual protocols.
This work is intended as an introduction to cryptographic security and a motivation for the widely used Quantum Key Distribution (QKD) security definition. We review the notion of security necessary for a protocol to be usable in a larger cryptographic context, i.e., for it to remain secure when composed with other secure protocols. We then derive the corresponding security criterion for QKD. We provide several examples of QKD composed in sequence and parallel with different cryptographic schemes to illustrate how the error of a composed protocol is the sum of the errors of the individual protocols. We also discuss the operational interpretations of the distance metric used to quantify these errors.