Anonymous Multi-Receiver Certificateless Hybrid Signcryption for Broadcast Communication

Confidentiality, authentication, and anonymity are fundamental security requirements in broadcast communication achievable by Digital Signature (DS), encryption, and Pseudo-Identity (PID) techniques. Signcryption, particularly hybrid signcryption, offers both DS and encryption more efficiently than “sign-then-encrypt”, with lower computational and communication costs. This paper proposes an Anonymous Multi-receiver Certificateless Hybrid Signcryption (AMCLHS) scheme for secure broadcast communication. AMCLHS combines public-key cryptography and symmetric key to achieve confidentiality, authentication, and anonymity. We provide a simple and efficient construction of a multi-recipient Key Encapsulation Mechanism (mKEM) to create a symmetric session key. This key, with the sender’s private key, is used in Data Encapsulation Mechanism (DEM) to signcrypt the message, ensuring confidentiality and authentication. The scheme generates identical ciphertext for multiple recipients while maintaining their anonymity by assigning a PID to each user. Security notions are demonstrated for indistinguishability against chosen-ciphertext attack using the elliptic curve computational diffie-hellman assumption in the random oracle model and existential unforgeability against chosen message attack under elliptic curve diffie-hellman assumption. The AMCLHS scheme operates in a multireceiver certificateless environment, preventing the key escrow problem. Comparative analysis shows that our scheme is computationally efficient, provides optimal communication cost, and simultaneously ensures confidentiality, authentication, anonymity, non-repudiation, and forward security.