  In known constructions of classical zero-knowledge protocols for NP, either
of zero-knowledge or soundness holds only against computationally bounded
adversaries. Indeed, achieving both statistical zero-knowledge and statistical
soundness at the same time with classical verifier is impossible for NP unless
the polynomial-time hierarchy collapses, and it is also believed to be
impossible even with a quantum verifier. In this work, we introduce a novel
compromise, which we call the certified everlasting zero-knowledge proof for
QMA. It is a computational zero-knowledge proof for QMA, but the verifier
issues a classical certificate that shows that the verifier has deleted its
quantum information. If the certificate is valid, even unbounded malicious
verifier can no longer learn anything beyond the validity of the statement. We
construct a certified everlasting zero-knowledge proof for QMA. For the
construction, we introduce a new quantum cryptographic primitive, which we call
commitment with statistical binding and certified everlasting hiding, where the
hiding property becomes statistical once the receiver has issued a valid
certificate that shows that the receiver has deleted the committed information.
We construct commitment with statistical binding and certified everlasting
hiding from quantum encryption with certified deletion by Broadbent and Islam
[TCC 2020] (in a black box way), and then combine it with the quantum
sigma-protocol for QMA by Broadbent and Grilo [FOCS 2020] to construct the
certified everlasting zero-knowledge proof for QMA. Our constructions are
secure in the quantum random oracle model. Commitment with statistical binding
and certified everlasting hiding itself is of independent interest, and there
will be many other useful applications beyond zero-knowledge.
