A controversy surrounding the AACS cryptographic key arose in April 2007 when the Motion Picture Association of America and the Advanced Access Content System Licensing Administrator, LLC (AACS LA) began issuing demand letters to websites publishing a 128-bit (16-byte) number, represented in hexadecimal as 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 (commonly referred to as 09 F9), which is one of the cryptographic keys for HD DVDs and Blu-ray Discs. The letters demanded the immediate removal of the key and any links to it, citing the anti-circumvention provisions of the U.S. Digital Millennium Copyright Act (DMCA). In response to widespread Internet postings of the key, the AACS LA issued various press statements, praising those websites that complied with their requests as acting in a "responsible manner", warning that "legal and technical tools" were adapting to the situation. The controversy was further escalated in early May 2007, when aggregate news site Digg received a DMCA cease and desist notice and then removed numerous articles on the matter and banned users reposting the information. This sparked what some describe as a digital revolt, or "cyber-riot", in which users posted and spread the key on Digg, and throughout the Internet en masse. The AACS LA described this situation as an "interesting new twist".

[Last contributor : Serrin , Content under LGPL licence]