A Generalized Group-Oriented Threshold Signcryption Schemes

A generalized group-oriented threshold signcryption scheme based on elliptic curve cryptosystem and Schnorr's signature schemes is proposed in this paper.This scheme simultaneously fulfills the(t,n) threshold signcryption and the(k,l) threshold shared verification,and it has improved the drawbacks of Wang et al.'s scheme and Hsu et al.'s scheme.Our scheme provides both confidentiality and authenticity for group communication with lower communication cost and more efficient computation.Without divulging recipient's private key and the message m,non-repudiation of sender is provided by means of public verifiability in our scheme.In addition,our scheme can achieve semantic security by preventing the message guess attack.