2008 Underhanded C Contest Officially Open

Xcott Craver writes "The 2008 Underhanded C Contest has just opened. Every year, contestants are asked to write a simple, innocent, readable C program that appears to perform an innocent task — but implements some non-obvious evil behavior. This year's challenge: redact blocks from an image, but do it so that the excised pixels can somehow be retrieved. We also have listed the winners of last year's contest, which was to write a simple encryption utility that mysteriously and undetectably fails between 1 percent and 0.1 percent of the time. The winning entry is truly impressive." We discussed the first of these contests in 2005.

Comments

PNG

[Saberwind]

The PNG specification allows for private (nonstandard) data chunks that can be flagged to be preserved by any program that doesn't understand them. That would seem to be the most straightforward way to hide redacted pixels in a recoverable way, at least if the input file is PNG.