Renowned computer security expert Bruce Schneier has an article up at the Guardian (thanks Slashdot) about the problems of taking your laptop with you through customs.

Last month a US court ruled that border agents can search your laptop, or any other electronic device, when you’re entering the country. They can take your computer and download its entire contents, or keep it for several days. Customs and Border Patrol has not published any rules regarding this practice, and I and others have written a letter to Congress urging it to investigate and regulate this practice.

But the US is not alone. British customs agents search laptops for pornography. And there are reports on the internet of this sort of thing happening at other borders, too. You might not like it, but it’s a fact. So how do you protect yourself?

I hadn’t heard about the pornography bit before, so I did a little Googling and it looks like this mainly means pedophilic materials. Though, since it’s much easier to automatically determine whether there’s pornography of any sort on a hard drive, than it is to distinguish between “regular” and “child-flavored” porn, I think it probably means that if they find substantial porn of any sort on your hard drive, you’ll be delayed and your laptop’s disk contents will be copied, or the laptop itself retained.

Anyway, the crux of the matter isn’t that I should be relieved that I will never have to worry about custom officials finding child pornography on a laptop as I travel abroad (since I don’t ever plan to possess any), but rather the fact that they do the scan at all, and even retain the “right” to keep my laptop or copy its contents.

The vast majority of my laptop contents are publicly available material. What’s not basic software packages downloadable from packages.ubuntu.com, is probably work-in-progress on things that I code on, like Wget. But I also have things like private encryption keys on there, some of which aren’t passphrase-protected. Someone with one of those would be able to get root access to my private servers on the Net. It’s not as if I host child porn there, either, but one common thread in government snooping is that they often use one pretext as an excuse for other purposes. If the government deemed me worth investigating (for whatever reasons), they wouldn’t hesitate to take advantage of the private keys on some old copy of my hard drive to do a lot more snooping, than they have a right to.

Schneier recommends destroying the browser cache and cookies, using secure deletion software to delete anything sensitive that you can, and using encrypted partitions or USB drives for the things you can’t do without (curiously, steganography wasn’t mentioned: I’d have thought this an ideal application).

It seems to me, though, far simpler to swap your normal laptop hard-drive with a “travel suitable” one, one that just has your necessities installed over a fresh new disk. Of course, this still doesn’t solve the problem of having sensitive-but-indespensible materials, for which you’d still want encrypted (and probably stealthed) partitions or USB drives.

While we’re on the subject of laptops and travel, note too that there are restrictions on packing lithium batteries and devices that contain them (in checked luggage: “there is generally no restriction on the number of spare batteries allowed in carry-on baggage“). (I saw this too on Slashdot first.)