A method of providing secure communications between a first and a second communications unit comprising a key exchange between the communications units resulting in a shared secret key, the key exchange including a user interaction. The method includes the steps of providing, at least partly by means of a user interaction, a passcode to the first and second communications units; generating a first contribution to the shared secret key by the first communications unit and a second contribution to the shared secret key by the second communications unit, and transmitting each generated contribution to the corresponding other communications unit; authenticating the transmitted first and second contributions by the corresponding receiving communications unit based on at least the passcode; and establishing said shared secret key by each of the communications units from at least the corresponding received first or second contribution, only if the corresponding received contribution is authenticated successfully.