In this project we try to put light on the Blockchain: how it emerged, how it works and why it is possibly one of the greatest technologies of the future. The blockchain, in big terms it's a big decentralized database, and based on these qualities described during the project, a proof of concept will be created based on Ethereum, one of the most known and important blockchains after Bitcoin, to take data protection, especially medical data, to a next level. To decentralize medical information and provide wide privacy to our data, it will develop a web application that will take the data from the blockchain. Smart contracts will be used are basically small scripts, that are stored in the Ethereum's blockchain. As if they were real contracts, it allows to comply accurate the rules that are described in them. The application will allow patients and doctors to share clinical information without it being stored centrally by hospitals or private doctors. The goal is to block all access to our data without prior consent. Do not give rise to possible leaks of patient medical records and data. The project has been designed using the Solidity and Javascript programming languages. During the development, it was used the operating system Ubuntu 16.04LTS and for the deployment of the Ethereum contracts, the test network has been used to reduce costs and reduce the time it takes for the blockchain to check each of the transaction. It has been achieved in this way, that this and other projects take advantage of the capabilities of technology in a simple way, allowing the owner of the data to be the final user.