In this section we present a purely graphical password selection and input scheme, which we call ``draw a secret'' (DAS). In this scheme, the password is a simple picture drawn on a grid. This approach is alphabet independent, thus making it equally accessible for speakers of any language. Users are freed from having to remember any kind of alphanumeric string.
The most compelling reason for exploring the use of a picture-based password scheme is that humans seem to possess a remarkable ability for recalling pictures (i.e., line drawings and real objects). The ``picture effect'', that is, the effect of pictorial and object representations on a variety of measures of learning and memory has been studied for decades [7,27,25,30,5]. Cognitive scientists have shown that there is a substantial improvement of performance in recall and recognition with pictorial representations of to-be-remembered material than for verbal representations.
Superiority in recall of objects over words in immediate recall and over short retention intervals has been demonstrated through a number of experiments. Empirical evidence of the power of pictures over words dates back to the 1800s; experiments performed by Calkins  showed the recall of words declining by or more over a 72 hour retention interval, and recall of objects dropping by less than over the same period. Studies exhibiting strikingly high differences in memory recall of pictures over words have since been replicated on numerous occasions [27,30,22,6]. Some theories that have been proposed to explain these experimental results are outlined in Appendix A.