An authentication system is provided using one-time passwords (OTPs) for user authentication. An OTP key may be stored on a different device than the device on which the OTP is generated. In an embodiment, the system described herein enables a combined authentication system, including the two separate devices communicating over a non-contact interface, to provide advantageous security features compared to the use of a single device, such as a hardware OTP token. One device may be a personal security device and the other device may be a reader device coupled to a host device via which access is being controlled.