The Internet of Medical Things(IoMT) has powerful cloud computing ability and efficient data collection ability, which can improve the accuracy and convenience of medical work. As most communications are over open networks, data should encrypted before uploading to ensure the confidentiality of sensitive user data. Searching for encrypted data has become a challenging problem. Public key Encryption with Keyword Search (PEKS) supports the search of encrypted data and provides data privacy protection. PEKS has become a trendy technology, but PEKS still has the following problems: 1. The cloud server, as a semi-honest but curious third party, is likely to return some wrong search results to save computing and bandwidth resources. 2. The single keyword search inevitably produces irrelevant results, wasting computing and bandwidth resources. 3. Most PEKS schemes use bilinear pairing, so the computational efficiency is relatively low. 4. PEKS schemes based on Public Key Infrastructure (PKI) or identity-based cryptography inevitably face problems with certificate management or key escrow. 5. Most PEKS schemes face serious security threats such as Keyword Guessing Attacks (KGA) and File Injection Attacks (FIA). To solve the above problems, we propose a new certificateless verifiable bilinear pair-free conjunctive keyword search encryption scheme(CLVPFCKS) for IoMT using multi-signature.

Remote data integrity auditing (RDIA) schemes can inspect the integrity of outsourced data. Anddeduplication improves the utilization of cloud storage space. Therefore, a considerable number ofremote data integrity auditing schemes with deduplication mechanism (RDIA-DE) have been proposedby researchers. However, most of these schemes suffer from the following shortcomings. Initially,these schemes rely on honest and trustworthy third-party auditors (TPAs), which were difficult toachieve in reality. Additionally, the computational overhead of the proof-of-ownership (PoW) algorithmsincreases linearly with the number of challenged data blocks. In this paper, we put forward anovel RDIA-DE scheme based on blockchain. This scheme utilizes smart contracts to conduct dataintegrity audits, thereby eliminating the dependency on TPA and penalizing malicious cloud storageproviders. Subsequently, we provided security proofs under the random oracle model (ROM). Ultimately,we conducted a performance analysis on six RDIA-DE schemes. The results demonstrate thatthe new scheme enjoys significant efficiency advantages.