Requirements that electronic documents should fulfil to replace those written on paper are: the authentication, integrity and confidentiality. However, as shown with three examples, other factors should also be considered including: the registration acts, in which the literal text of the document should be filed in a trustworthy manner during a long period of time; and the time stamping which, in our example, is undertaken at the same time as the signatory signs the document. Finally, we should consider the possibility of emulating the possession mechanism, in an effort to conserve the advantages so that the autonomy of the persons is empowered to execute transactions through a simple exchange.