AACS encryption key controversy
attempts by MPAA and AACS-LA to prevent the distribution of a cryptographic key
A controversy surrounding the AACS processing 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 cease and desist 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), a cryptographic key 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 United States Digital Millennium Copyright Act (DMCA).
In response to widespread Internet postings of the key, the AACS LA issued various press statements, praising websites that complied with their requests for acting in a "responsible manner" and 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 from 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, leading to a Streisand effect. The AACS LA described this situation as an "interesting new twist".
Background
Because the encryption key may be used as part of circumvention technology forbidden by the DMCA, its possession and distribution has been viewed as illegal by the AACS, as well as by some legal professionals. Since it is a 128-bit numerical value, it was dubbed an illegal number. Opponents to the expansion of the scope of copyright criticize the idea of making a particular number illegal.
Commercial HD DVDs and Blu-ray discs integrate copy protection technology specified by the AACS LA. There are several interlocking encryption mechanisms, such that cracking one part of the system does not necessarily crack other parts.
Begin with the source’s own compact description: “AACS encryption key controversy” is attempts by MPAA and AACS-LA to prevent the distribution of a cryptographic key. The dossier treats that line as a proposition to test through AACS, encryption and controversy, not as a finished interpretation.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 19, 2026. The linked authority identifier is Q22729. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2007.
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