Abstract Access control of data that are outsourced to cloud storage is a challenging problem because data owners lose direct control over outsourced data. Attribute‐based encryption (ABE) is a potential cryptographic solution to provide confidentiality and flexible sharing of these outsourced data. However, the traditional ABE schemes do not meet the need of the current dynamic environment where data access not only considers the user's static and inherent attributes but also takes the user's contextual information such as location and time of access. This paper presents an improved ABE scheme using blockchain technology that can handle the frequently changing location and time attributes of data users efficiently, leading to support for fine‐grained access control of cloud storage embedding contextual information in the access policy of ABE. A prototype implementation of the proposed ABE scheme using solidity on the Ethereum platform and the experimental evaluation in terms of performance and execution cost shows a promising result.

The rapid growth of Internet of Things and communication technology has provided a lot of scope for the improvement of the current healthcare services. Mobile healthcare system can be used to monitor patients’ real-time physiological information and can also help in detecting and providing emergency services to the patients. For early detection of emergency, two associated requirements are - patients’ physiological details to be received in regular intervals and the data should be processed efficiently in an automated way. Additionally, patients sensitive healthcare details need to be protected also. For his purpose, this paper proposes a blockchain-enabled emergency detection system that detects emergency conditions from patients’ encrypted physiological information without decryption and automatically triggers quick responses to provide healthcare services to the patients’ via nearby hospitals. The support of blockchain technology increases accountability, transparency, and trust concerning the storage, safeguarding, and sharing of patients’ data. We present a proof of concept of our proposal using Hyperledger Fabric, and we perform an experimental evaluation using Caliper benchmarking tool to demonstrate the performance of the system.