Towards DTW-based Unlock Scheme using Handwritten Graphics on Smartphones

Nowadays, due to the increasing capability, mobile devices especially smartphones have become a necessity in people's daily life, which would store a lot of personal and private information. This makes smartphones a major target for cyber-attackers, i.e., either loss of such mobile deices or illegal access will cause personal data breach and economic damage. Hence it is of great importance to safeguard smartphones from unauthorized access with the purpose of reducing the risk of privacy leakage and economic losses. To achieve this purpose, designing a suitable scheme to unlock phone screen is one promising solution. For instance, Android unlock scheme is a typical example, where users can unlock the phone screen by inputting a correct pattern. However, its password space is low due to the adoption of only nine dots on a 2D grid. In this work, we design a new unlock scheme using handwritten graphics, which uses an improved DTW-based algorithm for authentication. Also, we implement a prototype and evaluate our scheme using both a public dataset (SUSIG) and a self-collected dataset (SCD). Our results indicated that our scheme could achieve 7.12% and 8.75% EER on SUSIG and SCD respectively.