Are You a Math Genius?
The Dec 14, 2008 paper "Fingerprint and Inkjet-trace Imaging using Disulfur Dinitride", in ChemComm (Paul F. Kelly, Roberto S. P. King and Roger J. Mortimer), outlines a new real-world forensics technique which is mentioned in this episode. A mirrored, Gaussian-smoothed version of the S2N2 treated envelope is shown below. It's still difficult to read, though, even more than a typical Captcha. The really adventuresome can try using an optical character recognition system. Previous puzzles can be seen at the Math behind NUMB3RS pages.
Wolfram SpikeyPuzzles provided by Wolfram Research, Makers of Mathematica