Your general idea is right-on. If lots of folks use crypto, it'll be politically more difficult for the government to ban it. But do many browser users even //know// they're using an encrypted channel? Probably not. This is an education issue as well as a deployment issue.
I must admit that I didn't think much about crypto until this came up. You know, I think there are a couple of types of Libertarians. Type one says that government doesn't do anything right, because collectively they are incompetent, in the same way many people in big companies make bad decisions. Government is like the biggest company in the nation, with no profit pressure to restrain bureaucracy. In addition, government is a way to try and reconcile opposing views, and so we rarely get a "pure" version of anything - in fact, we often get contradictory results, such as tobacco subsidies colliding with tobacco restrictions. Because of this, smaller government is better - solve the tobacco problem by enacting /neither/ subsidies nor restrictions, and save a whole pile of money and effort. Type two says that government doesn't do anything right because of actual malicious actions within government - that government is a conspiracy between fat cat businessmen and nasty spooks, and that they very often, quite deliberately do the wrong thing. I've traditionally been a Type One libertarian, but I think you can only explain the current crypto efforts with Type Two. I must confess that I'm wondering what Seth Finkelstein, Pro-Government Warrior, able to jump over 50 Libertarians in a single bound, thinks of all this. Crypto restrictions are natural to oppose in a Libertarian world, due to our fundemental distrust of government. Where do they fit in a Liberal one? D