Abstract: The invention refers to a method for authorizing access to a third party application, called client (2), to protected resources owned by a user (1) and hosted in a server (3). The method comprising: the client being used by the user asking for a temporary token to the server; the server sending a first SMS to the user, said first SMS providing means to authenticate the user; authenticating the user by the means provided in previous two steps; the user authorizing the client; the server sending a second SMS to the user providing some information needed to obtain an access token; the client getting the information of the previous step from the user and the access token; the client accessing protected resources using the access token.