Generalization of signcryption for resources-constrained environments

Traditional signcryption is not feasible for some information security scenarios, though it is a new cryptographic primitive that simultaneously fulfills both the functions of signature and encryption. Generalized signcryption is an adaptive primitive which achieves both secrecy and authenticity or provides them respectively by a generic structure. The notions related to generalized signcryption such as syntax, correctness, and security are proposed in the paper. A practical generalized signcryption scheme ECGSC is evaluated carefully also. The formal proofs for the unforgeability and confidentiality of ECGSC in the Random Oracle model are provided. To give a solution for multiple user settings, an efficient multicast scheme is also designed. ECGSC will seamlessly switch to the Elliptic Curve Digital Signature Algorithm (ECDSA) or a provable secure asymmetric encryption scheme when recipient's keys or sender's keys are absent. Compared with other schemes, it saves 9-14% communication costs in the signcryption mode. It also saves 78-82% computational costs. Copyright (c) 2007 John Wiley & Sons, Ltd.