The ISC International Journal of Information Security

Abstract Confidentiality, unforgeability, and public verifiability are essential for secure multi-party communications. These communications play a vital role in real-world applications such as decentralized financial transactions, e-commerce, cloud computing, and web services, where authentication and privacy preservation are very important. In conventional cryptosystems, individual signcryption performed by each participant significantly increases the unsigncryption cost for the receiver. Multi-signcryption offers an efficient alternative by allowing multiple signers to jointly signcrypt a single message. This paper proposes a novel certificateless multi-signcryption scheme that eliminates the certificate management problem of traditional public key infrastructures and avoids the key escrow problem of identity-based cryptography. To reduce the computational cost associated with bilinear pairings over elliptic curves, the proposed scheme is designed in a pairing-free environment. This scheme achieves constant-time verification in the unsigncryption phase and is independent of the number of signers. Security is formally proven under the hardness assumptions of the Elliptic Curve Computational Diffie–Hellman Problem (ECCDHP) and the Elliptic Curve Discrete Logarithm Problem (ECDLP). The proposed scheme ensures confidentiality, unforgeability, and public verifiability, and it attains significantly lower computational costs than existing schemes. Hence, the proposed scheme can be used for secure group communications in resource-constrained environments where high performance is essential.