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.

In recent years, with the support of appropriate smart contract-based access control policies, blockchain technology has proven to be a compelling solution for providing a unified, trusted platform for resource sharing. However, due to the immutability property of blockchain, it can be challenging to patch or fix bugs after the deployment of a smart contract. Therefore, it is critical to ensure that the smart contract access control policies adhere to all specifications prior to their deployment, and the presence of anomalies within policies is not desirable. Thus, this paper proposes an automated policy verification and enforcement framework for Ethereum decentralized applications, which supports an automated off-chain policy verification before its deployment to the underlying blockchain. We integrate a verification engine within the off-chain module paired with a translator to convert XACML policies into Solidity smart contracts and vice-versa. Additionally, the experiments performed on benchmark XACML policies further reinforce the pragmatism of our proposal.