Expanded Conclusive Eavesdropping in Quantum Key Distribution

On conclusive eavesdropping and measures of mutual information in quantum key distribution

We address the question of quantifying eavesdropper's information gain in an individual attack on systems of quantum key distribution. It is connected with the concept of conclusive eavesdropping introduced by Brandt. Using the BB84 protocol, we examine the problem of estimating a performance of conclusive entangling probe. The question of interest depends on the choice of a quantitative measure of eavesdropper's information about the error-free sifted bits. The Fuchs--Peres--Brandt probe realizes a very powerful individual attack on the BB84 scheme. In the usual formulation, Eve utilizes the …