  In this paper, we propose a new efficient mediated semi-quantum key
distribution (MSQKD) protocol, facilitating the establishment of a shared
secret key between two classical participants with the assistance of an
untrusted third party (TP). Unlike existing MSQKD protocols, our approach
significantly reduces the quantum requirements for TP, who only needs to
prepare and measure qubits in the $X$ basis. Meanwhile, the classical
participants are limited to preparing and measuring qubits in the $Z$ basis,
along with performing Hadamard operations. This reduction in quantum overhead
enhances the practicality of our MSQKD protocol without compromising qubit
efficiency. Additionally, we demonstrate the security of our protocol against
various well-known attacks.
