分野別セミナー

Signcryption is a cryptographic primitive that fulfills both
the functions of digital signature and public key encryption
simultaneously, at a cost significantly lower than that required by
the traditional signature-then-encryption approach. Signcryption has
been shown to be useful in many applications, such as electronic
commerce, mobile communications and smart cards. Recently, three
identity-based signcryption schemes in the standard model were
proposed. However, the three schemes are broken soon. How to
construct a secure identity-based signcryption scheme in the
standard model is still an open problem. In this paper, we solve
this problem and propose an efficient identity-based signcryption
scheme in the standard model. We prove that our scheme has the
indistinguishability against adaptive chosen ciphertext attacks
under the modified decisional bilinear Diffie-Hellman assumption and
the existential unforgeability against adaptive chosen messages
attacks under the computational Diffie-Hellman assumption.