Let's not boil the ocean here. Many criminals use COTS solutions.
Disabling their technology in a way that is still provides satisfactory
for privacy for ordinary citizens would be a useful engineering goal
that pragmatically addresses both their need for privacy and the
need for law enforcement.
It seems to me there's some straightforward solutions here. As the
"Keys Under Doormats" paper notes, the same devices are used all over
the world and it is unlikely that countries would accept key escrow
that they don't control. Hence the obvious way to do key splitting is
to send a piece to the government of every country where they sell,
say, iPhones. If the governments of China, Vietnam, Pakistan, India,
Saudi Arabia, Israel, Nigeria, Venezuela, Bolivia, and Brazil (and the
US) all agree that something is bad enough to disclose, it must be
pretty bad.
On the other hand, if that's a bad idea, or it's ridiculous, I'd be
interested in seeing the research comparing the largly hypothetical
costs of secure crypto to the easily measured costs of having our
high tech devices shut out of all those markets.
R's,
John