Non‐malleable Extractor in the Presence of Classical or Quantum Side Information*

Non‐malleable extractor is an important tool for studying the problem of privacy amplification in classical and quantum cryptography with an active adversary. The randomness of the weakly‐random source X before privacy amplification always depends on the information adversary has, called side information. We study properties of such extractors in the presence of classical and quantum side information, and show that any non‐malleable extractor is essentially secure in the case where the adversary has classical side information. We also prove that non‐malleable extractors are quantumproof with uniform seed, or only require the seed to be weakly random.