Synthetic Worlds - Disappearing Cryptography

Cryptography Reference

In-Depth Information

sometimes complain about an tiny added bit of echo added as a wa-

termark. This process still continues to require an artist's touch.

15.5 Summary

There is no reason to stop with just moving lines of text or adding

echos. Any synthetic file can be tweaked during the construction.

The real challenge is creating detection algorithms that will detect

and extract the changes from the files. In some cases, the data is

readily available. An animated presentation developed in Macrome-

dia's Flash format, for instance, could encode information in the po-

sition and timing of the items. This data is easy to extract from the

files using the publicly distributed information about the file format.

If the data can't be extracted from the file many, many of the tech-

niques developed by the artificial intelligentisia for image and audio

analysis can be quite useful. Machine vision algorithms, for instance,

can extract the position and orientation of animated characters in a

movie. Echo detection and elimination tools used by audio engineers

can also help located echoes carring hidden information.

The Disguise Any synthetic file, be it text, sound, light, or maybe one

day smell, can carry information by tweaking the parameters

during synthesis.

How Secure Is It The security depends, to a large extent, on the na-

ture of the files and the skill of the artist. High-quality graphics

have many places where a slight twist of the head could carry

several bits of information without anyone noticing.

How to Use It Any of the steganographic techniques for tweaking

the least significant bits or adding in signals can be used on the

raw data used to guide the synthesis. To a large extent, all of the

techniques for steganography are just applied at an earlier step

in the process. For instance, an animator may choose the posi-

tion of a character's limbs and then feed this data to a render-

ing engine. The steganography is done just after the animator

chooses the position but before the rendering.