In the USA there is a piece of legislation called the DMCA (google for it if you've not heard of it). Among it's provisions, residents of the USA are prohibited from distributing anything that " is (or is a component of) a circumvention technology". This is part of a hexadecimal key, now revoked, that can be used in decrypting HD-DVD discs. Using this key and appropriate software, I can decrypt, and therefore watch, any HD-DVD disc that uses this key. If I were resident in the USA, then I would be in breach of this law.
In fact, I'm about to blatantly break that law again: 0.
My challenge to the MPAA's lawyers is to argue that, if I were resident in the USA, this publication is illegal. If they fail in that, then they surely have no argument that publication of the whole key (just another number) is illegal?
0 is a part of the key too, and if you do a search on google for "09-F9" (yet another hexadecimal number) you can find out a bit more about this.
Note that I have been very careful in this posting not to reveal the real value of this hexadecimal number, as even if you put the various parts I've hinted at together, you don't have the whole picture. I will leave it to the readers to do their own research if they wish to find the whole number.