In recent years, the explosive growth of mobile traffic has highlighted the issue of spectrum resource shortage. On one hand, most of the spectrum suitable for mobile communication has already been allocated; on the other hand, the existing spectrum below 6GHz has not been fully utilized. The mainstream solution is to allocate underutilized spectrum through spectrum auctions, but traditional spectrum auction methods can lead to privacy leakage issues. Therefore, we propose a secure spectrum sensing and sharing mechanism using blockchain and secure multiparty computation based on the EU’s ADEL framework. Our mechanism achieves comprehensive security and privacy protection in spectrum sensing and spectrum sharing. In the spectrum sensing phase, we implement decentralized secure spectrum sensing by leveraging the decentralized and trustworthy nature of blockchain, which protects the identity information of bidders and prevents both internal and external attackers from tampering with the sensing results. In the spectrum sharing phase, we safeguard the privacy of bidders’ location and bid information. Additionally, we conduct a security analysis of the mechanism, theoretically proving its security. Experimental simulations were conducted on the proposed secure spectrum sensing mechanism and privacy-preserving grouping algorithm. The results demonstrate the efficiency and practicality of the mechanism.