Secure Text Entry using a Virtual Radial Keyboard with Dynamically Resized Keys and Non-Intrusive Randomization

TL;DR

This work identifies weaknesses in existing secure VR text-entry methods and introduces a novel virtual radial keyboard that uses an alphabetic circular layout with dynamically resized keys and per-keystroke randomization. By randomizing rotation and space location after every keystroke, the method severely disrupts absolute spatial mappings while preserving relative key order, creating an exponential search space and improving resistance to keystroke inference attacks. In a within-subject study (N=30) comparing against ISPR and QWERTY, the radial keyboard demonstrates superior security against prediction attacks, albeit with slower entry speeds and higher perceived workload due to unfamiliarity. The results suggest the radial design is a promising secure VR text-entry approach, with future work focusing on learner gains, layout refinements, and visual enhancements to bolster usability while maintaining strong security guarantees.

Abstract

As virtual reality (VR) becomes more widely adopted, secure and efficient text entry is an increasingly critical need. In this paper, we identify a vulnerability in a state-of-the-art secure VR text entry method and introduce a novel virtual radial keyboard designed to achieve a balance between security with usability. Keys are arranged alphabetically in a circular layout, with each key selected by controller rotation and dynamically expanding to facilitate precise selection. A randomized rotation mechanism shifts the keyboard after each keystroke, preserving relative key positions while disrupting absolute spatial mappings to protect against inference attacks. We conducted a within-subject study (N=30) comparing our method with the prior secure technique and a standard QWERTY keyboard. Results showed that the radial keyboard significantly improves resistance to keystroke prediction attacks while incurring a tradeoff in entry speed and subjective workload due to the unfamiliar non-QWERTY layout. However, both quantitative trends and qualitative feedback indicate strong potential for performance improvements with practice. We also discuss design implications, possible interface refinements, and directions for future work, including layout variations and visual enhancements.

Figures (7)

• Figure 1: (a) The user enters "a" on the radial keyboard, which triggers the randomization and results in two possible keyboard configurations: (b) the selected key "a" expands to the left of the cursor position, identical to the previous state (c) the selected key expands to the right of the cursor position, and all keys are shifted clockwise for one key width.
• Figure 2: Box plots of identical character ratio (ICR) and semantic similarity (SS). The ICR and the SS results were significantly different between all conditions, except for the SS results between Radial and Radial_Basic. Note: Throughout all figures, significance levels are indicated as follows: * $p<.05$, ** $p<.01$, *** $p<.001$.
• Figure 3: Box plots of words per minute (WPM). The WPM results were significantly different between all conditions.
• Figure 4: Box plots of Total Error Rate Per Character (TER). The TER was significantly higher in the ISPR condition compared to the QWERTY condition.
• Figure 5: Box plots of System Usability Scale (SUS). The SUS results were significantly different between all conditions.