I’m not particularly proud of this one, but hey, it’s something, I guess. The code and example OpenIntents Safe integration are available, as are the paper itself and slides from the presentation.

BibTeX:

@InProceedings{filardo:visualid,
  author  = {Filardo, Nathaniel Wesley and Ateniese, Giuseppe},
  title   = {High-Entropy Visual Identification for Touch Screen Devices},
  booktitle={Proceedings of the 8th International Conference on Information
            Security Practice and Experience},
  series  = {ISPEC'12},
  year    = {2012},
  isbn    = {978-3-642-29100-5},
  location= {Hangzhou, China},
  pages   = {182--198},
  doi     = {10.1007/978-3-642-29101-2_13},
  publisher={Springer-Verlag},
  address = {Berlin, Heidelberg}
}