A client device, system, and method for constructing a two-factor password utilized by an authentication device to authenticate an accessing computer. The client device connects to the accessing computer through an input/output (I/O) port such as a USB connection. When a user desires to access a network, he enters a user ID, which is sent from the accessing computer to the client device. The client device includes a client application, which retrieves a second factor from an internal database, and combines the user ID and the retrieved second factor to form the two-factor password. The two-factor password is sent to the accessing computer, which transmits it to the authentication device. The accessing computer is authenticated only if both the user ID and the second factor match a user ID and second factor stored in the authentication device.