An Empirical Analysis of the Cascade Secret Key Reconciliation Protocol for Quantum Key Distribution

The need to share key material with authorized entities in a secure, efficient and timely manner has driven efforts to develop new key distribution methods. The most promising method is Quantum Key Distribution (QKD) and is considered to be “unconditionally secure” because it relies upon the immutable laws of quantum physics rather than computational complexity. Unfortunately, the non-idealities present in actual implementations of QKD systems also result in errors manifested in the quantum data channel. As a consequence, an important component of any QKD system is the error reconciliation protocol which is used to identify and correct inconsistencies in the exchanged key material. This research provides an empirical analysis of the Cascade secret key reconciliation protocol to measure its efficacy under different error rates, sampling rates, error distributions and larger sifted key sizes. The key findings of the research are that 1) an error sampling rate of 25% provides optimal Cascade performance when using variable block sizes, 2) the choice of sifted key length directly impacts the accuracy of Cascade error estimation, 3) the Cascade algorithm performs well in burst error environments with initial permutation, and 4) a tradeoff exists between buffer size and information leaked.