Seems there is a danger hidden in distributing officially unsanctioned data on CDs. There is a technical measure that allow tracking the CDs back to the writer they were created with. We should be aware about this for any scheme that relies on distribution of physical CD-R/RW media. According to Orange Book Part2 Ver 3.1, the CD recorders are supposed to write RID (Recorder IDentification Code), a 97-bit number identifying brand, type, and serial number of the recorder, every 100 frames in the Q-channel to all CD-R and CD-RW disks. There was something principially similar discussed here in 1999, related to Xerox using steganography for embedding serial number of the copier in color copies. Never trust a device whose firmware you can't audit... See: http://www.cdrinfo.com/Sections/Glossary/Details.asp?RelatedID=630 http://www.disctronics.co.uk/technology/glossary/glossary_qr.htm http://www.feurio.com/English/faq/faq_writer_snr.shtml http://www.licensing.philips.com/information/sid/