Identity-based ring signcryption scheme with constant size ciphertext

This paper presented an identity-based ring signcryption scheme without random oracle by using bilinear pairings.The size of the ciphertext was a constant and independent of the size of the ring.By introducing the selective identity and selective chosen message attack model,this paper proved unforgeability of the scheme under the hardness of DHI problem and its indistinguishability against selective identity and chosen ciphertext attack under the hardness of DBDHE problem.This scheme is more efficient compared with other ring signcryption schemes.