nothing is immune.  Any crypto is breakable by someone who is sufficiently smarter than the person who invented the crypto.   This is why crypto security is so hard.   There is always someone sufficiently smarter.<p>In general the strongest security is always physical security (attack dogs, machine guns, etc).   The problem with that, of course, is that someone more vicious might come along.  Also, physical security is somewhat vulnerable to physical degradation (earthquakes, fires, etc)  Also, physical security is pretty awkward to implement and maintain, plus it really complicates access and transfer of secured materials.