This challenge was given at DEFCON 16 and was a bit tricky I must say. I took approximately three hours to do it but it was mainly due to the fact that I was unable to find the good .pem file directly. The google dork given as hint sent a few results back in 2008, but now, there are hundreds of results! I went in circle asking what did I do wrong, and finally I decided to look for and try more keys. I finally found the good one on this site.
With this key I was able to decipher the messages. Here’s the method:
I always appreciate to work on these topics, as they make me learn new things and/or keep my knowledge up to date.