Click-based graphical passwords have attractive usability properties, such as cueing and good memorability. However, image size and number of click-points in each password significantly affect their security. We investigated the usability of such a graphical password system when its parameters were adjusted to provide security equivalent to (or better than) that of text passwords. We found that manipulating different parameters resulted in similar usability. This suggests that the preferred method for adjusting security can be dictated by the constraints of devices and preferences of users. For example, mobile devices might use smaller image sizes and more click-points. Keywords Authentication, graphical passwords, usable security ACM Classification Keywords K.6.5 Computing Milieux: Security and Protection – Authentication General Terms Experimentation, Human Factors, Security