Authentication in public spaces poses significant security risks. Most significantly, passwords can be stolen, potentially leading to fraud. A common method to steal a PIN is through an observation attack, either using a camera or through direct observation (e.g. shoulder-surfing). This paper addresses this problem by presenting the design and implementation of a novel input keypad which uses tactile cues as means to compose a password. In this system, passwords are encoded as a sequence of randomized vibration patterns, making it visually impossible for an observer to detect which items are selected. An evaluation of this system shows it outperforms previous interfaces which have used tactile feedback to obfuscate passwords. Author Keywords Tactile UI, security, PIN entry, user study ACM Classification Keywords H5.2. User Interfaces: Haptic I/O General Terms Security, Experimentation, Human Factors