The people working in my field also are quite skeptical of our ability to do this. It ultimately boils down to the problem of building complex systems that are reliable and that work, and that problem has long predated the problem of access to encryption keys.

Clipper took a relatively simple problem, encryption between two phones, and turned it into a much more complex problem, encryption between two phones but that can be decrypted by the government under certain conditions and, by making the problem that complicated, that made it very easy for subtle flaws to slip by unnoticed. I think it demonstrated that this problem is not just a tough public policy problem, but it's also a tough technical problem.

If it were possible to hold onto this sort of database and really be assured that only good guys get access to it, we might have a different discussion. Unfortunately, we don't know how to build systems that work that way. We don't know how to do this without creating a big target and a big vulnerability.

So, in 1993, in what was probably the first salvo of the first Crypto War, there was concern coming from the National Security Agency and the FBI that encryption would soon be incorporated into lots of communications devices, and that that would cause wiretaps to go dark. There was not that much commercial use of encryption at that point. Encryption, particularly for communications traffic, was mostly something done by the government.

On balance, the use of encryption, just like the use of good locks on doors, has the net effect of preventing a lot more crime than it might assist.

There's been a certain amount of opportunism in the wake of the Paris attacks in 2015, when there was almost a reflexive assumption that, "Oh, if only we didn't have strong encryption out there, these attacks could have been prevented." But, as more evidence has come out - and we don't know all the facts yet - we're seeing very little to support the idea that the Paris attackers were making any kind of use of encryption.

In order for any smartphone manufacturer to decrypt the data on your phone, it has to hold onto a secret that lets it get that access. And that secret or that database of secrets becomes an extremely valuable and useful target for intelligence agencies.