Boing Boing: EFF finds HUGE block of hidden info in new iTunes tracks

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Thursday, May 31, 2007

EFF finds HUGE block of hidden info in new iTunes tracks

Apple's new DRM-free tracks from the iTunes store not only contain your email address and ~~password~~ name in hidden fields, but in at least one case, more than 360k of hidden information. EFF's technologists have found a hidden block of data in the new iTunes tracks:

We compared two DRM-free copies of the track Daftendirekt by Daft Punk. When decoded to PCM/WAV data, both copies produced an identical audio signal (the MD5sum is e40b006497f9b417760ca5015c3fa937). So there is no audio watermark. But one of the .m4a files is almost 360K larger than the other!
We haven't finished examining these differences yet, and we don't have in-house expertise on MPEG codecs, but some of them have an intriguing amount of structure. There's a region (see around offset 0x11470 in the Daft Punk track for example) where the files contain what look like tables with sequential indices but different data in the table.
We'll post again if we learn more about what's going on here. In the mean time, some pure speculation: it may be that large amounts of iTunes library data are present in each file. It's also possible that Apple has found a way to watermark the AAC encoding itself, such that users would need to either crack the watermark or transcode the audio signal in order to produce a file that does not identify them as the source.

Link

posted by Cory Doctorow at 08:57:52 AM permalink | Other blogs' comments

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Support Bloggers' Rights! HOWTO: Get a link posted to Boing Boing Boing Boing Mobile powered by Winksite Fark rules! This work is licensed under a Creative Commons License permitting non-commercial sharing with attribution. Boing Boing is a trademark of Happy Mutants LLC in the United States [and other countries]. Stats (About our stats) defeat censorware Policies Our first five years' worth of posts in one file	View a recent day: June 10 \| June 09 \| June 08 \| previous days \| by month and year Thursday, May 31, 2007 EFF finds HUGE block of hidden info in new iTunes tracks Apple's new DRM-free tracks from the iTunes store not only contain your email address and ~~password~~ name in hidden fields, but in at least one case, more than 360k of hidden information. EFF's technologists have found a hidden block of data in the new iTunes tracks: We compared two DRM-free copies of the track Daftendirekt by Daft Punk. When decoded to PCM/WAV data, both copies produced an identical audio signal (the MD5sum is e40b006497f9b417760ca5015c3fa937). So there is no audio watermark. But one of the .m4a files is almost 360K larger than the other! We haven't finished examining these differences yet, and we don't have in-house expertise on MPEG codecs, but some of them have an intriguing amount of structure. There's a region (see around offset 0x11470 in the Daft Punk track for example) where the files contain what look like tables with sequential indices but different data in the table. We'll post again if we learn more about what's going on here. In the mean time, some pure speculation: it may be that large amounts of iTunes library data are present in each file. It's also possible that Apple has found a way to watermark the AAC encoding itself, such that users would need to either crack the watermark or transcode the audio signal in order to produce a file that does not identify them as the source. Link posted by Cory Doctorow at 08:57:52 AM permalink \| Other blogs' comments View a recent day: June 10, 2007 \| June 09, 2007 \| June 08, 2007 \| June 07, 2007 \| June 06, 2007 \| June 05, 2007 \| June 04, 2007 \| previous days \| all BB archives by month and year Email this entry to: Your email address: Message (optional):	Boing Boing Sponsored by: Your Text Ad Here Get BB by email: