Blockchain provides the possibility to design new types of applications and systems that allow their users to store data in a secure and transparent way. In this paper, we design a fully verifiable online electronic voting protocol using a blockchain. Our e-voting protocol, called VYV for Verify-Your-Vote, involves cryptographic primitives based on Elliptic-Curve Cryptography (ECC), pairings and Identity Based Encryption (IBE). It ensures the following privacy and security properties: only eligible voter can vote, authentication of the voter, vote privacy, receipt-freeness, fairness, individual and universal verifiability. Furthermore , we formally prove the security of our protocol, using ProVerif tool.