The blockchain is currently under the spotlight of trending technologies. It adds security to private applications in several areas of knowledge, and its versatility results in the development of multiple frameworks to meet the requirements of each application. Thus, it is a key challenge to ensure that blockchain frameworks provide security, access control, and high performance to applications. In this paper, we evaluate two frameworks for blockchain development, Parity, and Multichain, which provide configuration and permission flexibility. Our evaluation is a comprehensive comparison between the frameworks, focusing on the analysis of transaction-validation time, transaction-mining time, transaction-seek time and block-seek time. To this end, we deploy peer-to-peer private permissioned networks, in which the frameworks generate the blockchain applications. For each framework, we provide a realistic workload, based on the distribution of probability of interarrival time of transactions on the Bitcoin network. The results show that each framework stands out under specific criteria, and their design decisions imply restrictions on features that are critical for creating secure and efficient blockchain applications.@en

Electronic medical records (EMRs) are highly sensitive information shared among peers to keep up-to-date patient history. Providing security, privacy, and availability to these sensitive data is a challenge because, typically, after data publication the patient loses control over them. In this paper, we propose a blockchain-based approach to secure EMR for healthcare applications, where access control is patient-centric. Our proposal keeps encrypted EMRs in the blockchain, and the patient shares the decryption key only with healthcare professionals in which he/she trusts. Blockchain allows untrusted node, in a distributed peer-to-peer network to correctly and verifiably interact with each other, without any reliable intermediary. We investigate the scalability of our approach through simulations. Results show that it scales well since increasing the number of nodes in the network implies a linear increase in the size of the stored chain. Results also reveal that the time for inserting a new EMR in the blockchain remains low even when the number of nodes in the network increases.@en