So is is possible to engineer perfectly secure systems? Consider the law of the rodeo: "There's not a horse that's never been rode, and not a rider that's never been throwed." I like the analogy since it reminds us that all computer evil can be mitigated. But it always fights back. Good and evil will continue a fast paced rodeo dance long into the future.
To engineer secure systems for the future we need to continually assess where we are and what the near term future holds for our technologies.