Blockchain-Based Public Key Encryption with Multi-Keyword Search Secure against Inside Keyword Guessing Attacks

Abstract

In the last two decades, with the prevalence of Internet of Things (IoT) and cloud computing, many individuals and organizations have outsourced large amount of data to cloud server for storage. Outsourced data onto the cloud server contains sensitive information such as medical records, organization’s financial records etc. Thus, the privacy of data retrieved by the user must be protected. In order to ensure that user information is secure when retrieving data, searchable encryption technology for the cloud environment is used. However, most schemes only support single-keyword search and do not support updating files, which limits the flexibility of the scheme. To solve these problems, in this paper we developed a Blockchain-based public key encryption scheme with multi-keyword search (BC-PKEMS), which supports file update operations. Besides, we utilized a smart contract to ensure the fairness of transactions between the data owner and user without introducing a third party. Our scheme achieves verifiability during the data storage phase by numbering the files and ensuring that the ciphertext received by the user is complete. Security and performance analysis shows that our scheme is secure against inside keyword guessing attacks (KGAs) and has better computation and storage overhead than other existing schemes.