Steganographically hiding secret messages in fake fingerprints

In Towards Construction Based Data Hiding: From Secrets to Fingerprint Images, published in IEEE Transactions on Image Processing (Sci-Hub Mirror), two Fudan University computer scientists propose a fascinating method for hiding encrypted messages in fake fingerprints that are both visually and computationally difficult to distinguish from real ones, which could theoretically allow the use of fingerprint databases to convey secret messages.

The researchers' method encodes the encrypted message using the ridge endings and bifurcations of the fingerprint, in a way that current statistical methods for spotting hidden messages does not reliably detect (the fingerprints also look like real fingerprints, even to skilled observers).

Stegonography -- the science of hiding the existence of messages inside other files or works -- is a really fun technical field, full of skullduggery. But it's subject to a critical flaw, which is that analysis of a large number of source files without hidden messages yields up a statistical profile that can be compared to files that have stegonographically encoded messages hidden in them, and these comparisons usually spot the doctored files very quickly.

For example, people have long proposed hiding an image by flipping the least-significant bit in each pixel of an image -- in a 16-bit image, changing this bit only alters the color of the corresponding image by 1/65536 of its original value, which is effectively imperceptible. But bitmap compression algorithms tend to smooth out this kind of minor variation (specifically because it is imperceptible, and so the compression algorithm can safely throw away the associated information without perceptibly degrading the image). Read the rest