A method for providing authorized access to a service application in order to use a protected resource of an end user, said protected resource being an Application Programming Interface, API, and being exposed in OAuth protocol protected endpoints of a plurality of administrative domains, each administrative domain within said plurality of administrative domains belonging to a service provider and being responsible for individually issuing and controlling later use of authorizations to access to multiple protected resources, as granted by end user belonging to said administrative domain, characterised in that: - the method is applied to distributed OAuth scenarios where said endpoints of said plurality of administrative domains are previously unknown by said service application; - the OAuth protocol endpoints are unique and valid for getting authorizations to access any underlying API endpoint; - a global infrastructure supports application registration and credentials management; and in that the method further comprises: i. selecting, by an intermediate entity, an administrative domain of said plurality of administrative domains based on information of said end user and preferences provided during OAuth authentication phase; ii. routing, by said intermediate entity, an OAuth procedure to said selected administrative domain; iii. performing, by said selected administrative domain, a secure authorization to grant access to said end user by means of the OAuth protocol, the latter consisting at least of: - an authentication phase of said end user; and - providing said service application with an access token in order to allow access to said protected resource; and iv. providing, said selected administrative domain to said service application, once performed said secure authorization, direct or proxy access to said protected resource via one of said endpoints established by said intermediate entity, said intermediate entity routing API authorized requests, sent by said application to said administrative domain, based on said access token, wherein the method maintains full compatibility with OAuth 1.0 or 2.0 standards and does not require any special behavior from the application side but just to follow standard OAuth performance. - the method is applied to distributed OAuth scenarios where said endpoints of said plurality of administrative domains are previously unknown by said service application; - the OAuth protocol endpoints are unique and valid for getting authorizations to access any underlying API endpoint; - a global infrastructure supports application registration and credentials management; and in that the method further comprises: i. selecting, by an intermediate entity, an administrative domain of said plurality of administrative domains based on information of said end user and preferences provided during OAuth authentication phase; ii. routing, by said intermediate entity, an OAuth procedure to said selected administrative domain; iii. performing, by said selected administrative domain, a secure authorization to grant access to said end user by means of the OAuth protocol, the latter consisting at least of: - an authentication phase of said end user; and - providing said service application with an access token in order to allow access to said protected resource; and iv. providing, said selected administrative domain to said service application, once performed said secure authorization, direct or proxy access to said protected resource via one of said endpoints established by said intermediate entity, said intermediate entity routing API authorized requests, sent by said application to said administrative domain, based on said access token, i. selecting, by an intermediate entity, an administrative domain of said plurality of administrative domains based on information of said end user and preferences provided during OAuth authentication phase; ii. routing, by said intermediate entity, an OAuth procedure to said selected administrative domain; iii. performing, by said selected administrative domain, a secure authorization to grant access to said end user by means of the OAuth protocol, the latter consisting at least of: - an authentication phase of said end user; and - providing said service application with an access token in order to allow access to said protected resource; and - an authentication phase of said end user; and - providing said service application with an access token in order to allow access to said protected resource; and iv. providing, said selected administrative domain to said service application, once performed said secure authorization, direct or proxy access to said protected resource via one of said endpoints established by said intermediate entity, said intermediate entity routing API authorized requests, sent by said application to said administrative domain, based on said access token,