LAUSR

We present how the mechanisms of quantum Darwinism allow for information leakage in the standard BB84 quantum key distribution protocol, a paradigmatic prepare-and-measure quantum cryptography scenario. We work within the decoherence theory framework and employ the model of measurements provided by quantum Darwinism. We investigate how much of the information about the results crucial for the cryptographic key to be kept secret is leaked during the quantum measurement process and subsequently how much of that information might be later obtained by an eavesdropper using a type of so-called Van Eck side-channel wiretapping. We also show how security can be affected by different ways of organizing the surrounding environment into layers, e.g., rooms or other divisions affecting the spread of quantum information in the environment and its interaction, paving a venue for potential enhancements, and insight into proper engineering of shieldings for cryptographical devices.