Social Signature: Signing by Tweeting

In many application contexts, qualified electronic signature appears difficult to be adopted both for the cost of smart cards and qualified certificates and for the complexity of the signing, verification, registration and certificate management.However, the European legislation allows us to use electronic signatures when application scope of the signature is limited. As a consequence, designing new signature protocols that relax the heaviest features of qualified electronic signature in favor of usability and cheapness is a timely and important issue. In this paper, we propose a new lightweight e-signature protocol with a good level of security, not using public key cryptography and dedicated devices. The protocol is conceived for closed domains of users, such as the case of document exchanges between citizens and municipal public offices or private companies and employees. According to the protocol, signature functions are spread out over the popular social network Twitter, without requiring changes of its features, so that the adoption of our solution appears both realistic and effective.