Iranian Society of Cryptology The ISC International Journal of Information Security 2008-2045 14 1 2022 01 01 An Efficient Pairing-Free Identity-Based Certificateless Signcryption 69 82 135755 10.22042/isecure.2021.261788.587 EN Saeed Banaeian Far Department of Electrical and Computer Engineering, Science and Research Branch Islamic Azad University, Tehran, Iran 0000-0003-2520-8492 Maryam Rajabzadeh Assar Department of Electrical and Computer Engineering, Science and Research Branch Islamic Azad University, Tehran, Iran Journal Article 2020 12 12 A certificateless (CL) signcryption scheme is a cryptographic primitive that provides user authentication and message confidentiality at the same time. CL signcryption schemes (as a type of certificateless encryption scheme) have solved problems concerning malicious server presentation, and the server who issues users' partial private keys and certificates cannot obtain users' signing keys. Therefore, the CL signcryption scheme is an excellent choice for protecting users' signing keys and providing user authentication and message confidentiality. Moreover, signcryption schemes have lower computational costs than signature and encryption schemes. <br />The present study presents a short and efficient CL signcryption scheme based on the hyperelliptic curve (HC). Applying HC as the calculation base for designing the presented CL signcryption scheme reduces key-length from 160 bits to 80. The presented CL signcryption scheme is shorter than other recently-proposed ones with regard to communication overhead with its less than one-third shorter length compared to the shortest of the others. Moreover, it is more efficient than other recently-proposed CL signcryption schemes in the user-side computational cost, including the \textit{key generation} and \textit{user key generation} phases that have been halved in total. Finally, the security of the presented CL signcryption scheme was analyzed in the random oracle (RO) model based on the hardness of the point factorization problem (PFP) on HC. https://www.isecure-journal.com/article_135755_a2c4bb8b0dd37cd719c5ad5f6e7257b5.pdf