Mastodawn

TIL about the “Free Speech Flag”: https://en.wikipedia.org/wiki/Free_Speech_Flag

It’s an encoding of a secret key – 09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0 – that was used to copy protect HD DVDs and Blue Ray discs in the mid-2000s. This key was considered a so called “illegal number” since publishing it was tantamount to breaking a legally protected encryption scheme.

The flag consists of five colours whose RGB hex values are the first 15 bytes of the secret key and the C0 is printed in the lower right.

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Mark Reid

I had been aware of the original DeCSS “illegal prime” from the late 90s / early 2000s, as well as the textbook I used for my undergrad cryptography course – Schneier’s “Applied Crypotgraphy” – being classified by the NSA as a non-exportable munition but somehow missed this later development and flag.