Blockchain based hierarchical semi-decentralized approach using IPFS for secure and efficient data sharing

Nowadays, cloud servers are gathering an increasing amount of data. Data is commonly stored on cloud servers in the form of ciphertext to protect security and concealment of data. When a consumer requests to access of encrypted data, a third party must provide an access key. The system's security, however, will be compromised if the third party or internal personnel are dishonest. To address this issue, a novel blockchain-based secure...