Computational Soundness of Non-Malleable Commitments

This paper aims to find a proper security notion for commitment schemes to give a sound computational interpretation of symbolic commitments. We introduce an indistinguishability based security definition of commitment schemes that is equivalent to non-malleability with respect to commitment. Then, we give a construction using tag-based encryption and one-time signatures that is provably secure assuming the existence of trapdoor permutations. Finally, we apply this new machinery to give a sound interpretation of symbolic commitments in the Dolev-Yao model while considering active adversaries.