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 colours, with each colour providing three bytes of the key. The sixteenth byte "C0" is appended in the lower right corner.
Hexadecimal is a base-16 numeral system used in the fields of computer programming and mathematics. 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. 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.
