Adam Liptak, who has been on a roll lately, has another great “Sidebar” in today's NYT entitled, If Your Hard Drive Could Testify …. The article quotes me and Orin Kerr as if we were opposed; oddly, although I think Orin and I do have disagreements about what the law on encryption should be, I suspect Orin and I agree with each other on the points for which we're actually quoted.
Although the article does a great job of describing some recent cases and issues, the academic in me wishes that every time anyone writes about this stuff they'd have the space and time to provide what I see as some critical context for the debate as to when a person can be forced to hand over the key to a cryptosystem.
There are plenty of technical issues here (what happens if you really have forgotten your password? or if someone has put random gunk on your hard drive, making it look like there's crypto there?), but even more important fundamental ones. In particular, the current debate over the extent to which the 5th Amendment protects encrypted messages matters so much because our understanding of the 4th Amendment has changed. A hundred years ago, the Supreme Court thought it was obvious that asking a person to turn over his private papers was a constitutional violation. Even 30 years ago the Court thought that the 4th Amendment protected some zone of private papers such as a diary from demands that they be turned over. (Note that there can be an important difference between finding something in a search and demanding that the subject of the search find it for you.) Today, although the Supreme Court has never actually decided the diary issue, it's pretty clear that no other writing — and probably not the diary either — is protected from such demands.
It's the evisceration of the 4th that puts such pressure on the 5th. It may be that as a society we really don't want to allow any zone of privacy beyond what you can keep in your head. But as devices record more of our lives, and as we rely increasingly on what some of us only half-jokingly call our prosthetic memories, I think that it is increasingly unrealistic to exclude at least some bits from the intimate zone of privacy if we wish to remain true to the purposes of the 5th (and 4th) Amendments.