A Novel Pairing Free Revocable Certificateless Encryption With Ciphertext Evolution for Healthcare System

With the advancement of modern healthcare systems, patients now utilize medical sensor nodes to generate health data. These data are then transmitted to healthcare providers for analysis and diagnosis of the patient. These data are sensitive in nature and, therefore, need to preserve their privacy, security, and confidentiality. Another crucial aspect of a healthcare system is the effective revocation of malicious users. Revocable encryption schemes, particularly those with ciphertext evolution, have emerged as promising solutions. However, all the existing revocable schemes with ciphertext evolution have expensive bilinear pairing, map-to-point hash, modular exponentiation operations, rendering them unsuitable for resource constrained medical sensor nodes. In this paper, we propose a novel pairing free revocable certificateless encryption scheme with ciphertext evolution. Also, we prove that our scheme is secure against adaptive chosen ciphertext attacks. Our comparative analysis demonstrates that our scheme achieves substantial reductions in total computational cost by 74.9% to 86.4% and reduces ciphertext communication cost by 45.9% to 72.9%, making it the most effective among related schemes.