There is provided a computer-implemented method for authentication, the method comprising: defining a demanded level of security in an authorization service of a server; providing at least one authentication mechanism comprising at least one instance for at least one client; providing a policy comprising a security level for the at least one instance; receiving at least one request from the client to the server; authenticating the request based on the policy and the demanded level of security by the authentication service; and permitting the request if the demanded level of security is reached.