<p>Blockchain technology offers immutable evidence in decentralized data management in modern medical systems. However, securing Electronic Medical Records (EMR) within the blockchain framework remains a critical challenge due to the inherent storage limitations and computational overhead from existing public key methods. To address such issues, this paper proposes a certificateless hybrid signcryption scheme that integrates a tag-based key encapsulation mechanism (tag-KEM) with a data encapsulation mechanism (DEM), to enable secure and efficient EMR data management. Our approach addresses key limitations in existing blockchain systems by combining lightweight cryptographic operations based on Elliptic Curve Cryptography(ECC) with efficient decentralized off-chain storage to accommodate large-scale on growing health data. By employing ECC operations, the scheme significantly reduces computational complexity and enhances blockchain transaction throughput. Results from our experimental analysis shows a 40.01%–97.71% reduction in computational cost compared to the other existing methods. Additionally, findings from the decentralized off-chain analysis indicate significant improvements in storage efficiency and system performance, underscoring the scheme’s practicality for real-world data security applications.</p>