An efficient signcryption scheme with shortened ciphertext

Signcryption is a novel cryptographic primitive that prove confidentiality and authenticity simultaneously. In bandwidth-constrained environments, the data mount of ciphertext is the crucial factor that holds back its broad application. While most of the known schemes based on discrete logarithm problem and RSA problem, have the low communication performance. Based on BLS signature scheme, an efficient signcryption scheme with shortened ciphertext is proposed in this paper. It is provable secure in random oracle model under GDH (Gap Diffie-Hellman) assumption. With the present secure parameters, the data rate of proposed scheme is 76%. With the long term secure parameters, the data rate is 73%. It has the highest communication performance in all of the known schemes.