2.  Personal Greenspun set: The Personal Greenspun images can be downloaded from  http://www.photo.net/philip-greenspun/ photos/digiphotos/.  The thumbnails as well as the filename of the 400 Personal Greenspun  images can be found in the Per- sonal Greenspun  thumbnail page. ²  Google  set: The Google  images can be downloaded by following the hyperlinks or the URLs listed in the Google thumbnails page, accessible from the dataset website. ²  Recaptured PRCG  set: As the recaptured PRCG are the reproduc- tion of the PRCG, the distribution of these images is limited by the copyright. As a result, the Recaptured PRCG  will not be distributed. 9   Conclusions This technical report explains the needs for a new dataset catering for the PIM versus PRCG classification problem of the passive-blind image authen- tication research. During the process of working on the mentioned problem, we have designed and implemented a dataset that specifically takes into account the unbiased diversity of content, reliability of sources, and ad- vanced CG rendering techniques. This Columbia Photographic Images and Photorealistic Computer Graphics Dataset is to be made available to the research community and this technical report will serve as a user guide for the dataset. We make the data set open and publicly accessible in order to promote active interest and broad collaboration in this exciting area. 10   Acknowledgements This project is supported in part by NSF CyberTrust program (IIS-04- 30258) and Singapore A*STAR scholarship (for the first author). The au- thors thank Philip Greenspun for granting us the permission of using his personal images and Lexing Xie for her kind help. References [1]  I. J. Cox, M. L. Miller, and J. A. Bloom,  Digital Watermarking, ser. The Morgan Kaufmann Series in Multimedia Information and Systems. Morgan Kaufmann, 2002. 21