Abstract
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In modern applications, such as Electronic Voting, e-Health, e-Cash, there is a need that
the validity of a signature should be verified by only one responsible person. This is opposite to
the traditional digital signature scheme where anybody can verify a signature. There have been
several solutions for this problem, the first one is we combine a signature scheme with an encryption
scheme; the second one is to use the group signature; and the last one is to use the strong designated
verifier signature scheme with the undeniable property. In this paper, we extend the traditional
digital signature scheme to propose a new solution for the aforementioned problem. Our extension is
in the sense that only a designated verifier (responsible person) can verify a signer’s signature, and
if necessary (in case the signer refuses to admit his/her signature) the designated verifier without
revealing his/her secret key is able to prove to anybody that the signer has actually generated the
signature. The comparison between our proposed solution and the three existing solutions shows
that our proposed solution is the best one in terms of both security and efficiency.