Composability in quantum cryptography

TL;DR

This paper reviews the concept of composability in quantum cryptography, focusing on quantum key distribution security criteria and the universal composability framework for secure protocol composition.

Contribution

It provides an overview of composability principles in quantum cryptography and illustrates their practical application in generating secure key streams and complex cryptographic scenarios.

Findings

Quantum key distribution protocols can be securely composed within larger applications.

The universal composability framework ensures security when combining multiple cryptographic protocols.

Sequential composition of QKD rounds enables continuous secure key generation.

Abstract

In this article, we review several aspects of composability in the context of quantum cryptography. The first part is devoted to key distribution. We discuss the security criteria that a quantum key distribution protocol must fulfill to allow its safe use within a larger security application (e.g., for secure message transmission). To illustrate the practical use of composability, we show how to generate a continuous key stream by sequentially composing rounds of a quantum key distribution protocol. In a second part, we take a more general point of view, which is necessary for the study of cryptographic situations involving, for example, mutually distrustful parties. We explain the universal composability framework and state the composition theorem which guarantees that secure protocols can securely be composed to larger applications