From: Rich Gauszka 

Apple knows were your music goes?

http://www.macrumors.com/

Following the discovery that Apple was embedding iTunes account information
in iTunes Plus songs, Erica Sadun at O'Reilly speculates that Apple may be
using Steganography within the AAC portion of iTunes Plus tracks.

The conclusion came after purchasing the same iTunes Plus song from the
iTunes Store using two accounts. After having stripped the files of their
meta data (where iTunes would store account information, and any extraneous
information), she compared the files and found 774 bytes (out of 6.7 MB)
were different in the AAC data itself. Her conclusion: "Clearly some
sort of fingerprinting/steganography is going on in the data itself."

The EFF has apparently also begun investigating the issue, although they do
not indicate how far they will pursue the issue.

Most forum users appear to not be dissuaded by the revelations, and appear
to accepting the move as a compromise allowing music companies to have some
recourse against those who illegally share music, but opening the DRM
restrictions for legitimate users.

Of note, Apple does not indicate that it uses such technology in its iTunes
Terms of Service.

Steganography (from Wikipedia): "the art and science of writing hidden
messages in such a way that no one apart from the intended recipient knows
of the existence of the message." Different from cryptography in that
the existence of the message itself is not disguised, but the content is
obscured.

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