ID-based Signcryption Scheme with (t, n) Shared Unsigncryption

An identity-based signcryption scheme with (t, n) shared unsigncryption is proposed, which is the integration of the signcryption scheme, the (t, n) threshold scheme and zero knowledge proof for the equality of two discrete logarithms based on the bilinear map. In this scheme, any third party can verify the validity of the signature, but only more than t members in the recipient group can cooperatively recover the message m. As compared to the Zhang et al.’s signcryption scheme with (t, n) shared unsigncryption based on discrete logarithms, the proposed scheme has the following advantages: it provides both public verifiability and forward security; the key management problem is simplified because of using identity-based cryptosystem.