Abstract: Mercurial commitment scheme is an interesting variation of regular com-
mitment scheme, which additionally allows for a soft decommit stage. The
soft decommitments are not required to binding but can not con°ict with the
true decommmitments (if the true decommmitments exist). In our paper, we
consider reusable non-malleable mercurial commitment schemes. Reusable
non-malleability is that the adversary accesses to an arbitrary number of
commitments, which is a strictly stronger security notion than general non-
malleability in which the adversary has access to only one commitment. We
adopt the reusability mainly due to the inherent property of mercurial com-
mitment scheme. We introduce the notion of reusable non-malleable mercu-
rial commitment scheme and give a construction based on the multi-trapdoor
mercurial commitment scheme.

Key words: commitment, non-malleable, mercurial, multi-trapdoor