As demand for data privacy and secure communication grows in areas like the Internet of Things, healthcare, and smart city infrastructure. A reliable way to achieve these requirements is key agreement. Current key agreement protocols often struggle to handle the wide gap in computing power between terminal devices and servers. To tackle this issue, this paper proposes a novel Asymmetric Three-Party Key Agreement Protocol Based on Secure Multiparty Computation. By merging the Diffie-Hellman key exchange mechanism with the complexity of Subset Product Problem (NP-complete), the scheme strategically offloads heavy computation to high-performance nodes, while terminals with limited resources only carry out necessary lightweight operations. This approach significantly reduces the overall computational and communication load without compromising security in the key negotiation process. Meanwhile, the design incorporates a trusted third party (TTP) solely for assisting in key generation and final result computation, enhancing anonymity and privacy protection without revealing any party’s data sources.