I wish to congratulate you. You have done something I did not really expect. You almost broke our authentication mechanism. I genuinely feel humbled and wish to pay you my deepest respect. Reapers can be proud.
The message you have intercepted and decoded, as you have undoubtedly figured out, was not meant for you. It is directed mainly to our sympathizers in Liberty who do not have the means to contact us. Its distributed nature allows us to smuggle fragments of code into various broadcasts. While the puzzle can be rather easily solved even by the Little Squeaky Fiends, it is technically impossible to trace a read and thus allowing our potential recruits to contact us safely, even if they are under strong surveillance. The encryption key allows us to retrieve the message and verify it.
And you have almost broke it. You have correctly assumed Rijndael 256 bit algorithm, but most likely used wrong encryption key and initialization vector, and thus received a false positive. The key was simply hashed name of our organization while the vector was simply the hashed key. And you were also correct that the key contained coordinates, however, only in the fourth dimension.
If I was wearing a hat, I would say that it is off to you. Now we will have to change some of our security protocols.