Methods and apparatuses in a client terminal (400) and a web server (402) for enabling safe communication between said terminal and server. When the terminal obtains a web page from the server in a session, the terminal creates a context-specific key, Ks_NAF′, based on one or more context parameters, P1, . . . Pn, pertaining to said session and/or web page. The terminal then indicates the context-specific key in a login request to the server, and the server determines a context-specific key, Ks_NAF′, in the same manner to verify the client if the context-specific key determined in the web server matches the context-specific key received from the client terminal. The context-specific key is thus bound to and valid for the present context or session only and cannot be used in other contexts or sessions.