Non-malleable Commitments Against Quantum Attacks

We construct, under standard hardness assumptions, the first non-malleable commitments secure against quantum attacks. Our commitments are statistically binding and satisfy the standard notion of non-malleability with respect to commitment. We obtain a log(star) (lambda)-round classical protocol, assuming the existence of post-quantum one-way functions. Previously, non-malleable commitments with quantum security were only known against a restricted class of adversaries known as synchronizing adversaries. At the heart of our results is a new general technique that allows to modularly obtain non-malleable commitments from any extractable commitment protocol, obliviously of the underlying extraction strategy (black-box or non-black-box) or round complexity. The transformation may also be of interest in the classical setting.