OK, so the special chars are XOR masks for each following string, and that implies you have to base64 decode each string separately.
Almost 1 month has passed. Nobody solved this.
Here is the solution: https://dimme.net/the-solution-to-the-riddle
I think that unless you offer some sort of reward, few people will put in the time to write the code even if they strongly suspect the XOR portion.
