Alien cosmic rays

What if ultra high energy cosmic rays are signals from an alien intelligence? If aliens want to communicate, they should use a signal that will not be confused with a natural source. Photons are the obvious first choice, but there so many natural photons out there that it's hard to be heard above the din. Cosmic rays, protons, are different. The fact that they carry so much energy and have no easy natural explanation immediately calls attention to them. Two open questions remain: Even if we allow artificial methods, how are they produced and survive the journey through space? And how can we decode information contained in them? Just how much information, if any, can one encode in a proton?