A Multireceiver Certificateless Signcryption (MCLS) Scheme

User authentication and message confidentiality are the basic security requirements of high-end applications such as multicast communication and distributed systems. Several efficient signature-then-encrypt cryptographic schemes have been proposed to offer these security requirements with lower computational cost and communication overhead. However, signature-then-encryption techniques take more computation time than signcryption techniques. Signcryption accomplishes both digital signature and public key encryption functions in a single logical step and at a much lower cost than ``signature followed by encryption.\u27\u27 Several signcryption schemes based on bilinear pairing operations have been proposed. Similarly, anonymous multi-receiver encryption has recently risen in prominence in multicast communication and distributed settings, where the same messages are sent to several receivers but the identity of each receiver should remain private. Anonymous multi-receiver encryption allows a receiver to obtain the plaintext by decrypting the ciphertext using their own private key, while their identity is kept secret to anyone, including other receivers. Among the Certificateless Multi-receiver Encryption (CLMRE) schemes that have been introduced, Hung et al. proposed an efficient Anonymous Multireceiver Certificateless Encryption (AMCLE) scheme ensuring confidentiality and anonymity based on bilinear pairings and is secure against IND-CCA and ANON-CCA. In this paper, we substantially extend Hung et al.’s multireceiver certificateless encryption scheme to a Multireceiver Certificateless Signcryption (MCLS) scheme that provides confidentiality along with authentication. We show that, as compared to Hung et al.’s encryption scheme, our signcryption scheme requires only three additional multiplication operations for signcryption and unsigncryption phases. Whereas, the signcryption cost is linear with the number of designated receivers while the unsigncryption cost remains constant for each designated receiver. We compare the results with other existing single receiver and multireceiver signcryption schemes in terms of number of operations, exemption of key escrow problem, and public key settings. The scheme proposed in this paper is more efficient for single and multireceiver signcryption schemes while providing exemption from the key escrow problem, and working in certificateless public key settings

Homomorphic Trapdoors for Identity-based and Group Signatures

Group signature (GS) schemes are an important primitive in cryptography that provides anonymity and traceability for a group of users. In this paper, we propose a new approach to constructing GS schemes using the homomorphic trapdoor function (HTDF). We focus on constructing an identity-based homomorphic signature (IBHS) scheme using the trapdoor, providing a simpler scheme that has no zero-knowledge proofs. Our scheme allows packing more data into the signatures by elevating the existing homomorphic trapdoor from the SIS assumption to the MSIS assumption to enable packing techniques. Compared to the existing group signature schemes, we provide a straightforward and alternate construction that is efficient and secure under the standard model. Overall, our proposed scheme provides an efficient and secure solution for GS schemes using HTDF

A Novel Approach to e-Voting with Group Identity Based Identification and Homomorphic Encryption

This paper presents a novel e-voting scheme that combines Group Identity-based Identification (GIBI) with Homomorphic Encryption (HE) based on the discrete logarithmic assumption. The proposed scheme uses the Schnorr-like GIBI scheme for voter identification and authorization using Zero-Knowledge (ZK) proof to ensure the anonymity and eligibility of voters. The use of Distributed ElGamal (DE) provides fairness and receipt-freeness, while the use of partial shares for decryption enables individual and universal verifiability without the need for a central authority. Voters can maintain uncoerability by encrypting their votes and casting ballots based on their own choice. The proposed scheme is secure under various scenarios and robust in the Random Oracle (RO) model. The GIBI-HE scheme offers a promising solution for e-voting, providing a sustainable and accessible environment for voters while supports unreusability of votes and protecting privacy of voter