User authentication on mobile devices: Approaches, threats and trends

Mobile devices have brought a great convenience to us these years, which allow the users to enjoy the anytime and anywhere various applications such as the online shopping, Internet banking, navigation and mobile media. While the users enjoy the convenience and flexibility of the "Go Mobile" trend, their sensitive private information (e.g., name and credit card number) on the mobile devices could be disclosed. An adversary could access the sensitive private information stored on the mobile device by unlocking the mobile devices. Moreover, the user's mobile services and applications are all exposed to security threats. For example, the adversary could utilize the user's mobile device to conduct non-permitted actions (e.g., making online transactions and installing malwares). The authentication on mobile devices plays a significant role to protect the user's sensitive information on mobile devices and prevent any non-permitted access to the mobile devices. This paper surveys the existing authentication methods on mobile devices. In particular, based on the basic authentication metrics (i.e., knowledge, ownership and biometrics) used in existing mobile authentication methods, we categorize them into four categories, including the knowledge-based authentication (e.g., passwords and lock patterns), physiological biometricbased authentication (e.g., fingerprint and iris), behavioral biometrics-based authentication (e.g., gait and hand gesture), and two/multi-factor authentication. We compare the usability and security level of the existing authentication approaches among these categories. Moreover, we review the existing attacks to these authentication approaches to reveal their vulnerabilities. The paper points out that the trend of the authentication on mobile devices would be the multi-factor authentication, which determines the user's identity using the integration (not the simple combination) of more than one authentication metrics. For example, the user's behavior biometrics (e.g., keystroke dynamics) could be extracted simultaneously when he/she inputs the knowledge-based secrets (e.g., PIN), which can provide the enhanced authentication as well as sparing the user's trouble to conduct multiple inputs for different authentication metrics. (C) 2020 Elsevier B.V. All rights reserved.