randextract: a Reference Library to Test and Validate Privacy Amplification Implementations

Quantum cryptographic protocols do not rely only on quantum-physical resources, they also require reliable classical communication and computation. In particular, the secrecy of any quantum key distribution protocol critically depends on the correct execution of the privacy amplification step. This is a classical post-processing procedure transforming a partially secret bit string, known to be somewhat correlated with an adversary, into a shorter bit string that is close to uniform and independent of the adversary's knowledge. It is typically implemented using randomness extractors. Standardization efforts in quantum cryptography have focused on the security of physical devices and quantum operations. Future efforts should also consider all algorithms used in classical post-processing, especially in privacy amplification, due to its critical role in ensuring the final security of the key. We present randextract, a reference library to test and validate privacy amplification implementations.