Paper 2023/780

An Anonymous Multireceiver Hybrid Signcryption for Broadcast Communication

Abstract

Confidentiality, authentication, and anonymity are the basic security requirements in broadcast communication, that can be achieved by Digital Signature (DS), encryption, and pseudo-identity (PID) techniques. Signcryption offers both DS and encryption more efficiently than "sign-then-encrypt,". However, compared to hybrid signcryption, it has higher computational and communication costs. Our paper proposes an Anonymous Multi-receiver Certificateless Hybrid Signcryption (AMCLHS) 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 symmetric session key, along with the sender's private key, is used in Data Encapsulation Mechanism (DEM) to signcrypt the message, thus providing confidentiality and authentication. It also generates identical ciphertext for multiple recipients while keeping their identities private by assigning a PID to each user. Our scheme demonstrate notions for Indistinguishability under Chosen-Ciphertext Attack using Elliptic Curve Computational Diffie-Hellman assumption in random oracle. It also demonstrates security for Existential Unforgeability against Chosen Message Attack using Elliptic Curve Diffie-Hellman assumption. The AMCLHS scheme operates in a multireceiver certificateless environment, preventing the key escrow problem. We show that, compared to existing schemes, our scheme is computationally efficient, provides optimal communication cost, and simultaneously ensures security properties such as confidentiality, authentication, anonymity, non-repudiation, and forward security.