A user-interfacing device (31, 41, 51) for authenticating a user to a plurality of coupled computers using a single smart-card characterized by: - at least two computer channels, for interfacing with at least two computers, each of said at least two computer channels having: ∘ a computer interface capable of interacting with a respective coupled computer of the plurality of coupled computers; ∘ a smart-card reader function (2x, 42x, 45x) capable of being coupled to said respective coupled computer via said computer interface, wherein said smart-card reader function has a card-presence input (14, 47x); ∘ a smart-card interface line coupled to said smart-card reader function; and - a smart-card connector capable of receiving a user authentication smart-card; - a channel select switch (22, 46, 46a) having common ports coupled to said smart-card connector and switchable ports, wherein each of said switchable ports is coupled to one of the smart-card interface lines; and - a card presence switch, mechanically coupled to said smart-card connector and electrically coupled to each one of the card-presence inputs for indicating if a smart-card is inserted into the smart-card connector; wherein: - the interfacing device is capable of authenticating to said at least two computers only if said smart-card is inserted into said smart-card connector; - the interfacing device is capable of maintaining authentication to said at least two computers simultaneously; - and wherein once said smart-card is removed from said smart-card connector, the authentication session with all coupled computers is terminated at once. - at least two computer channels, for interfacing with at least two computers, each of said at least two computer channels having: ∘ a computer interface capable of interacting with a respective coupled computer of the plurality of coupled computers; ∘ a smart-card reader function (2x, 42x, 45x) capable of being coupled to said respective coupled computer via said computer interface, wherein said smart-card reader function has a card-presence input (14, 47x); ∘ a smart-card interface line coupled to said smart-card reader function; and ∘ a computer interface capable of interacting with a respective coupled computer of the plurality of coupled computers; ∘ a smart-card reader function (2x, 42x, 45x) capable of being coupled to said respective coupled computer via said computer interface, wherein said smart-card reader function has a card-presence input (14, 47x); ∘ a smart-card interface line coupled to said smart-card reader function; and - a smart-card connector capable of receiving a user authentication smart-card; - a channel select switch (22, 46, 46a) having common ports coupled to said smart-card connector and switchable ports, wherein each of said switchable ports is coupled to one of the smart-card interface lines; and - a card presence switch, mechanically coupled to said smart-card connector and electrically coupled to each one of the card-presence inputs for indicating if a smart-card is inserted into the smart-card connector; wherein: - the interfacing device is capable of authenticating to said at least two computers only if said smart-card is inserted into said smart-card connector; - the interfacing device is capable of maintaining authentication to said at least two computers simultaneously; - and wherein once said smart-card is removed from said smart-card connector, the authentication session with all coupled computers is terminated at once. - the interfacing device is capable of authenticating to said at least two computers only if said smart-card is inserted into said smart-card connector; - the interfacing device is capable of maintaining authentication to said at least two computers simultaneously; - and wherein once said smart-card is removed from said smart-card connector, the authentication session with all coupled computers is terminated at once.