If you have the original file saved on your computer, the decryption key is:
"ACollectionOfDiplomaticHistorySince_1966_ToTh e_Pr esentDay#" (minus quotes)

Decryption software:
http://www.aescrypt.com/download.html (open source, safe download)

If you don't have original file downloaded, you can download the now decrypted file here (torrent):
https://thepiratebay.org/torrent/6644050/ (personally unverified as I had the original file downloaded)

Enjoy!