The key is an ordinary number most widely known by its hexadecimal representation; in decimal notation, it is 13,256,278,887,989,457,651,018,865,901,401,704,640.
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.
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 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 compromised players can still be used to view old discs, but not newer releases without encryption keys for the compromised players.
Therefore, the "09 F9" key is only one of many parts that are needed to play a disc on an unlicensed player.
The AACS system can be used to revoke a key of a specific playback device, after it is known to have been compromised, as it has for Win DVD.
The byte "C0" is appended in the lower right corner.
Internet users began circulating versions of this image, calling it the Free Speech Flag, in blog posts on dozens of websites and as user avatars on forums such as Digg.
The first fifteen bytes of the 09 F9 key are contained in the RGB encoding of the five colors, with each color providing three bytes of the key.
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.
Hexadecimal is a base-16 numeral system used in the fields of computer programming and mathematics.
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.