  In this paper we resolve an open problem regarding resettable zero knowledge
in the bare public-key (BPK for short) model: Does there exist constant round
resettable zero knowledge argument with concurrent soundness for $\mathcal{NP}$
in BPK model without assuming \emph{sub-exponential hardness}? We give a
positive answer to this question by presenting such a protocol for any language
in $\mathcal{NP}$ in the bare public-key model assuming only
collision-resistant hash functions against \emph{polynomial-time} adversaries.
