I think it is hard to be accurate about the finite capabilities of groups of engineers when trying to solve complex problems. I think the most honest thing each of us can say when faced with a new and complex problem is that we simply do not know what the answer is, but there may be someone else does. Putting aside the silver bullet analogy for a moment, there are quite a few case studies that show that genuine security is achievable when fundamental principles of security followed. One example of this is the secure radio communication technology that the U.S. employed in WWII, and which the enemy was never able to break.