Short signcryption scheme with public verifiability

Abstract

Signcryption is such a public key cryptographic primitive that simultaneously provides the functionality of signature and encryption within a single logic step. Despite the flurry of recent results on signcryption, there are no signcryption schemes which possess both tight security and short expansion. This paper presented a short signcryption scheme to achieve both above merits. Thanks to q-strong Diffie-Hellman problem and parings, our scheme is quite efficient and security, the signcryption operation has almost the same cost as an El Gamal encryption while the reverse operation only requires one pairing evaluation and two exponentiations, the ciphertext expansion is about 260 bits which is much smaller than that of all previously proposed schemes, and the security of our scheme is tightly related to q-Strong Diffie-Hellman problem in the random oracle model. © Springer-Verlag Berlin Heidelberg 2006.