The latest smartphones have started providing multiple authentication options including PINs, patterns, and passwords (knowledge based), as well as face, fingerprint, iris, and voice identification (biometric-based). In this article, we conducted two user studies to investigate how the convenience and security of unlocking phones are influenced by the provision of multiple authentication options. In a task-based user study with 52 participants, we analyze how participants choose an option to unlock their smartphone in daily life. The user study results demonstrate that providing multiple biometric-based authentication choices does not really influence convenience, because fingerprint had monopolistic dominance in the usage of unlock methods (111 of a total of 115 unlock trials that used a biometric-based authentication factor) due to users’ habitual behavior and fastness in unlocking phones. However, convenience was influenced by the provision of both knowledge-based and biometric-based authentication categories, as biometric-based authentication options were used in combination with knowledge-based authentication options—pattern was another frequently used unlock method. Our findings were confirmed and generalized through a follow-up survey with 327 participants. First, knowledge-based and biometric-based authentication options are used interchangeably. Second, providing multiple authentication options for knowledge-based authentication may influence convenience—both PINs (55.7%) and patterns (39.2%) are quite evenly used. Last, in contrast to knowledge-based authentication, providing multiple authentication choices for biometric-based authentication has less influence on choosing unlock options—fingerprint scanner is the most frequently used option (134 of 187 unlock methods used among biometric-based authentication options).

中文翻译：

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关于在智能手机上提供多种身份验证选择的安全性和可用性影响

最新的智能手机已开始提供多种身份验证选项，包括 PIN、图案和密码（基于知识），以及面部、指纹、虹膜和语音识别（基于生物特征）。在本文中，我们进行了两项用户研究，以调查提供多种身份验证选项如何影响解锁手机的便利性和安全性。在一项包含 52 名参与者的基于任务的用户研究中，我们分析了参与者在日常生活中如何选择解锁智能手机的选项。用户研究结果表明，提供多种基于生物特征的身份验证选择并不会真正影响便利性，因为由于用户的习惯行为和解锁手机的速度，指纹在解锁方法的使用中具有垄断优势（总共 115 次解锁试验中有 111 次使用基于生物特征的身份验证因素）。然而，便利性受到基于知识和基于生物特征的身份验证类别的提供的影响，因为基于生物特征的身份验证选项与基于知识的身份验证选项结合使用——图案是另一种常用的解锁方法。我们的研究结果通过对 327 名参与者的后续调查得到证实和概括。首先，基于知识和基于生物特征的身份验证选项可以互换使用。其次，为基于知识的身份验证提供多种身份验证选项可能会影响便利性——PIN 码 (55.7%) 和模式 (39. 2%) 使用非常均匀。最后，与基于知识的身份验证相比，为基于生物特征的身份验证提供多种身份验证选择对选择解锁选项的影响较小——指纹扫描仪是最常用的选项（在基于生物特征的身份验证选项中使用的 187 种解锁方法中的 134 种）。