Deep branding for iTunes Plus files?
ITunes Plus files could be identified with the name of the account from which they were purchased not only in the metadata, but directly in the song's digital code. The suspicion that Apple uses a very sophisticated technique to dissuade customers to indiscriminately distribute songs without Drm Erica Sadun, the Mac expert who had already discovered the 'light' branding in metadata.
To suspect a deep and readable code only by those who know the decoding system, as well as the presence, are the different sizes of the same file downloaded with two different accounts. Although there is no evidence that this is determined precisely by a coding system, I suspect that things are so strong, given that Sadun notes that the difference in size equal to the difference of 10 bytes, or the difference that exists between two usernames used to download the same song.
The technique used, which can be considered a sort of digital watermarking, is also being examined by the Electronic Frontier Foundation, an American association that deals with privacy and rights in the digital age. Even the EFF would in fact have detected substantial differences between files downloaded with different accounts and is investigating the matter.