If we try to prohibit encryption or discourage it or make it more difficult to use, we're going to suffer the consequences that will be far reaching and very difficult to reverse, and we seem to have realized that in the wake of the September 11th attacks. To the extent there is any reason to be hopeful, perhaps that's where we'll end up here.

What encryption lets us do is say, "Yes, the Internet is insecure." Bad guys are able to compromise computers everywhere, but we're able to tolerate that because if they do intercept our messages, they can't do any harm with it.

As the local police department might want to decrypt a phone of a criminal suspect, so would the Chinese or the Russian or the Iranian intelligence agencies like to be able to do exactly the same thing.

From a policymaker's point of view, [the back door] must look like a perfect solution. "We'll hold onto a separate copy of the keys, and we'll try to keep them really, really safe so that only in an emergency and if it's authorized by a court will we bring out those keys and use them." And, from a policy point of view, when you describe it that way, who could be against that?

It's only after you get down into the technical weeds - and they are admittedly rather weedy - that it becomes clear that this is much harder than it seems and not something we're going to be able to solve.

The security of computers and the Internet is a horrible and dangerous mess. Every week we hear about breaches of databases of Social Security numbers and financial information and health records, and about critical infrastructure being insecure.

It may be true that encryption makes certain investigations of crime more difficult. It can close down certain investigative techniques or make it harder to get access to certain kinds of electronic evidence. But it also prevents crime by making our computers, our infrastructure, our medical records, our financial records, more robust against criminals. It prevents crime.