Privacy Amplification in Quantum Cryptography BB84 using Combined Univarsal 2 -Truly Random Hashing

Abstract

The Quantum Cryptography BB84 protocol is considered to be the most widely used in Quantum Key Distribution (QKD) to create secure keys that are shared between communicating parties. Major phases in this protocol are the correction of discrepancies between keys of sender and receiver as well as the privacy amplification phase where two communicating parties distill highly secret shared key from a larger body of a shared key, which is only partially secret. In the present paper, we propose enhancing the performance of the privacy amplification phase by introducing message digests (MD) hash functions combined with truly random functions. The resulting Hash-Mod and Hash-Div functions are used to compress reconciled keys resulting from the error correction phase. Experiments were conducted using three different simulators to assess the performance of these combined functions using entropy and information measures. The newly introduced functions were tested against the plain versions of Mod and Div functions as well as the permutated Mod and Div functions using hash function signature size (MD4-128). The results supported the use of Hash-Mod and Hash-Div over the plain versions as well as their permuted versions in enhancing the entropy behavior and minimizing information content within reconciled key strings.