nvisible input and output modalities, such as haptics and audio, are a potentially effective defense against observation-based attacks on PIN entry systems. However, the successful implementation of such systems calls for some general design guidelines. The featured Web extra is a video of Andrea Bianchi, Ian Oakley and Dong-Soo Kwon showing how haptics and audio input and output modalities can help keep passwords safe for users of ATMs and other devices.