Certificate-Based Secure Three-Party Signcryption Scheme With Low Costs *

Abstract

A signcryption scheme combining public key encryptions and digital signatures can simultaneously satisfy the security requirements of confidentiality, integrity, authenticity and non-repudiation. In a three-party communication environment, a message signcrypted by one party might have to be securely delivered to the other two and they usually inde- pendently decrypt the ciphertext and verify recovered signature. Consequently, traditional signcryption schemes of single-recipient setting are not applicable. In this paper, we elabo- rate on the certificate-based cryptosystem to propose a provably secure three-party sign- cryption scheme from bilinear pairings. The security requirement of confidentiality against indistinguishability under adaptive chosen-ciphertext attacks (IND-CCA2) and that of un- forgeability against existential forgery under adaptive chosen-message attacks (EF-CMA) are proved in the random oracle model. Moreover, our scheme enables each recipient to solely reveal the signer's original signature for public verification without extra compu- tational efforts when the case of a later dispute over repudiation occurs. To the best of our knowledge, the proposed scheme is the first provably secure signcryption considering three-party communication environments.