Wearable technologies such as smart-glasses can sense, store and display sensitive personal contents. In order to protect this data, users need to securely authenticate to their devices. However, current authentication techniques, such as passwords or PINs, are a poor fit for the limited input and output spaces available on wearables. This paper focuses on eyewear and addresses this problem with a novel authentication system that uses an alphabet of simple tapping patterns optimized for rapid and accurate input on the temples (or arms) of glasses. Furthermore, it explores how an eyewear display can support password memorization by privately presenting a visualization of entered symbols. A pair of empirical studies confirm that performance during input of both individual password symbols and full passwords is rapid and accurate. A follow-up session one week after the main study suggests using a private display to show entered password symbols effectively supports memorization.