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PassPoints : Design and Evaluation of a Graphical Password System

Computer security depends largely on passwords to authenticate human users. However, users have difficulty remembering passwords over time if they choose a secure password, i.e., a password that is long and random. Therefore, they tend to create short and insecure passwords. Graphical passwords, which consist of clicking on pictures rather than typing alphanumeric strings, may help to overcome the problem of secure and memorable passwords. In this paper we describe PassPoints, a new and more secure graphical password system. We report an empirical study comparing the use of PassPoints to alphanumeric passwords. Participants created and practiced either an alphanumeric or graphical password. The participants subsequently carried out three longitudinal trials to input their password over the course of five weeks. The results show that the graphical password group created a valid password with fewer difficulties than the alphanumeric group. However, the graphical group took longer and made more errors in carrying out the practice. In the longitudinal trials the two groups performed similarly on memory of their password, but the graphical group took more time to input a password. INTRODUCTION Today's world of networked computing can be a frightening and dangerous place with attackers, hackers, crackers, scammers, and spammers at work. Computer security, which was relatively simple in pre-network days, is now a major and expensive problem for organizations and individuals. Constant attention to security is needed to protect against damage or theft of one's electronic assets. A home computer user installing high-speed internet service and a wireless network cannot even begin without a strong firewall, up-to-date virus protection, and 128-bit encryption. As Edward Tenner writes in his book Why Things Bite Back, "The price of protection is chronic vigilance" (1997, p. 243). The community of security researchers and practitioners has evolved rapidly in response to threats, on the one hand increasing vigilance in practice and, on the other hand, driving research innovation. Until recently the security problem has been formulated as a technical problem. However, it is now becoming widely recognized that security is also fundamentally a humancompuer interaction (HCI) problem (Patrick, Long & Flinn, 2003; Dourish, 2004). Most security mechanisms cannot be effective without taking into account the user. HCI matters in two ways: the usability of the security mechanisms themselves and the interaction of the security mechanisms with user practices and motivations. One of the key areas in security research and practice is authentication, the determination of whether a user should be allowed access to a given system or resource. Traditionally, alphanumeric passwords have been used for authentication. Today other methods, including biometrics and smart cards (Scholtz & Johnson, 2002; Coventry, De Angeli & Johnson, 2003), are possible alternatives. However, passwords are likely to remain dominant for some time because of drawbacks of reliability, security, or cost of other technologies (Brostoff & Sasse, 2000). In particular, smart cards also need PINs and passwords; biometrics, on the other hand, raise privacy concerns. Passwords also have drawbacks, most notably in terms of memorability and security. This has led to innovations to improve passwords. One such innovation is graphical passwords, that is, passwords that are based on pictures rather than alphanumeric strings. The underlying idea is that using pictures will lead to greater memorability and decrease the tendency to choose insecure passwords, which will in turn increase overall password