New Identity-Based Hybrid Signcryption

Signcryption is a cryptography primitive that combines both the functions of digital signature and public key encryption in a logical single step,at lower computational costs and communication overheads than the traditional signature-then- encryption approach.The KEM-DEM construction was first performed by Cramer and Shoup in 2003.Dent primitive proposed a signcryption KEM-DEM model hybrid structure in 2004.In 2006,Dent and Bj?rstad built one more efficient insider security of tag-KEM/DEM hybrid signcryption scheme using tag-kems.Fagen Li extended the concept of signcryption KEM-DEM to the identity-based setting in 2009,and proposed an identity-based hybrid signcryption of KEM-DEM structure.The main work in this paper is researching on the identity-based hybrid signcryption.The main results are as follows:1. we investigate the possibility of constructing identity-based tag-KEM/DEM hybrid signcryption scheme using tag-kems techniques,in which tag is an arbitrary binary string,the basic idea behind a signcryption tag-KEM is that the key encapsulation algorithm provides what amounts to a signature on the tagτ.The security properties of the proposed hybrid signcryption scheme are proven in the random oracle model,it is IND-CCA2 security in confidentiality and sUF-CMA security in unforgeability. The hybrid signcryption scheme is proved to be secure assuming the bilinear Diffie-Hellman problem is hard.2. Based on this setting,we propose an identity-based signcryption tag-KEM scheme.The proposed scheme is proved to be provable security, ciphertext authentication and ciphertext anonymity in the random oracle model.We discuss and analyse the properties of forward security, public verifiability, provable security, ciphertext unlinkability, ciphertext authentication and ciphertext anonymity of the scheme and so on.The proposed scheme only requires one pairing operation in signcryption and three pairing operations in unsigncryption,so the efficiency is higher.