We present barriers to provable security of two important cryptographic primitives,
perfect non-interactive zero knowledge (NIZK) and
non-interactive non-alleable commitments:
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Black-box reductions cannot be used to demonstrate adaptive soundness (i.e., that soundness holds even if the statement to be proven is chosen as a function of the common reference string) of any statistical NIZK for NP based on any “standard” intractability assumptions.
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Black-box reductions cannot be used to demonstrate non-malleability of non-interactive, or even 2-message, commitment schemes based on any “standard” intractability assumptions.
We emphasize that the above separations apply even if the construction of the considered primitives makes a
non-black-box use of the underlying assumption.
As an independent contribution, we suggest a taxonomy of game-based intractability assumptions.