Secure and efficient authentication using plug-in hardware compatible with desktops, laptops and/or smart mobile communication devices such as iPhones

A portable apparatus removably and communicatively connectable to a network device for communicating authentication credentials for a user in connection with either (i) the user logging into a network site or (ii) the user entering into a transaction with the network site, comprising:

• a communications port configured to connect and disconnect the apparatus to and from the ND and to establish a communication link between the apparatus and the ND when connected;
• and
• a processor disposed configured to (1) receive, from a network security server via the port, a secure message, readable only by the processor and not by the ND, including a personal identification number (PIN) for authenticating the user to the network site, and (2) either (i) transfer, via the port, the received PIN to an application associated the network site and executing on the ND or (ii) cause the apparatus to display the received PIN to the user for manual transfer of the PIN to the application associated the network site;
• wherein the PIN corresponds to a secret shared only by the security server and the network site, and not by the user, and is not associated with any particular user.