Proxy Re-Encryption for Secure Data Sharing with Blockchain in Internet of Medical Things

The Internet of Medical Things (IoMT) is crucial in our daily health monitoring and assisting doctors in treatment. However, the existing schemes mainly use cloud servers to solve the storage of large amounts of data generated by smart devices, ignoring the guarantee mechanism of ciphertext integrity, which may result in data being tampered with or replaced in data sharing. To address this issue, we propose a secure data sharing scheme named Proxy Re-Encryption for Secure Data Sharing with Blockchain in Internet of Medical Things (PRE-IoMT). Specifically, we propose a new proxy re-encryption data sharing approach by introducing identity hash during the key generation phase to realize the binding of public key and user identity, thus enhancing the security of data sharing in PRE-IoMT. Moreover, we adopt BlockChain transactions to design a pairing function ciphertext check mechanism, which can effectively prevent the ciphertext stored in the cloud server from being tampered with. We add the user to the accumulator by invoking the BlockChain smart contract to realize the management and fast query of users. Finally, we conduct the performance analysis experiments on the four-stage computation of proxy re-encryption, communication overhead, storage overhead, transmission delay, and the delay of BlockChain transactions, compared with existing schemes, our scheme improves the computation efficiency of encryption, re-encryption, decryption, and re-decryption by about 23.8%, 71.4%, 48%, and 15.3% respectively. The security proof also exhibits that PRE-IoMT can resist IND-ID-CPA.