A Verifiably Encrypted Signature Scheme with Strong

A verifiably encrypted signature can convince the verifier that a given cipher-text is the encryption of a signature on a given message. It is often used as a building block to con-struct optimistic fair exchange. In this paper, first we define a stronger unforgeable model, then give a variant of Cha-Cheon’s signature [8] and construct a verifiably encrypted signature based on this variant scheme. Finally, the scheme is proven to secure in random oracle model. In comparison with Gu et.al ’s verifiably encrypted signature scheme, our scheme is more efficient with respect to the size of signature and computation cost of signature