The rapid adoption of cloud-Internet-of-Things (CIoT) systems in biomedical human-cyber-physical systems (HCPS) has raised significant concerns regarding data security, privacy, and scalability. To address these challenges specifically within healthcare environments, we propose a novel IBS-ECDHE framework that integrates Identity-Based Signatures (IBS) and Elliptic Curve Diffie-Hellman Ephemeral (ECDHE) key exchange to provide robust and lightweight security for biomedical HCPS. Our framework leverages blockchain technology to decentralize identity management and access control, ensuring secure authentication and maintaining the integrity of sensitive biomedical data exchanged between IoT-enabled medical devices. By incorporating smart contracts, we automate key management and enforce stringent privacy and data integrity guarantees critical to biomedical applications. The proposed system was implemented on a Windows 10 PC and evaluated using various performance metrics, including authentication time, message size, transaction latency, and computational overhead. Experimental results demonstrate that IBS-ECDHE reduces authentication time by up to 76 % compared to traditional PKI systems, decreases message size by 40 %, and achieves lower blockchain transaction latency. The system also ensures scalability and energy efficiency, with parallel processing reducing latency by 37 %. The innovation of this approach lies in the combination of IBS with ECDHE for mutual authentication and the use of blockchain for decentralized identity management and secure real-time biomedical data exchange. This solution offers substantial improvements in security, privacy, and performance, making it highly suitable for next-generation biomedical HCPS.