The idea of signcryption is to provide a method to encrypt and sign data together in a way that is more efficient
than using a signature scheme combined with an encryption scheme. A new identity-based threshold signcryption scheme
is presented based on the bilinear pairings, which proves its semantic security on the hardness of decisional bilinear
diffie-hellman(DBDH)problem and its unforgeability on the hardness of computational diffie-hellman(CDH) problem in
the random oracle model. In addition, the scheme is proved to be efficient.