Introduction

Randomness extractors are functions that map weakly random variables to near-uniform variables. These functions have far-reaching applications including derandomisation in computational complexity theory, list-decodable error-correcting codes and, perhaps most notably, quantum cryptography.

In quantum cryptography, tasks such as key distribution and random number generations have a number of crucial (classical) post-processing subroutines. Randomness extractors play a fundamental role in realizing these, for example, providing an explicit technique to purify a shared raw secret key (known as privacy amplification) and/or distil near-perfect randomness from a weakly random raw output string (known as randomness extraction) in the presence of an adversary.

Recent years have seen major advances in theoretical and experimental quantum cryptography, including exciting proof-of-concept demonstrations and even commercialized products. All of these require a suitable randomness extractor with the appropriate implementation complexity, loss/error and security.

To facilitate these advances, we have developed Cryptomite, a software library with multiple randomness extractor implementations. This software library offers state-of-the-art randomness extractors that are easy to use, optimized and numerically precise providing a trade-off of features that suits numerous practical use cases today.