Posted on Sat - January 21, 2006

Securing your thumb drive

No doubt about it, thumb drives are one of the easiest ways yet to do a sneakernet. Beats the heck out of floppies. Until I get a Bluetooth Palm with a big memory card, it's the easiest I'll have access to.

This is one of those tricks that I thought everyone knew, but someone saw me do it and was amazed.

The problem with a thumb drive is that any computer that can recognize it can also access the files on it. But there is an easy fix, at least on a Macintosh running OS X.

Open Disk Utility (Applications/Utilities) and create an encrypted read/write disk image on the thumb drive. Be sure to make it big enough to hold your secure files, but not so big as to crowd out other space on the thumb drive. On a 250 Mb thumbdrive, I have the disk image Fate that takes up 100 Mb.

The default encryption is 128-bit. Nothing is totally secure, but a 128 bit would require serious computing power by today's standards to crack. We're talking years of computing time on a standard desktop computer. That is the secret to security, it is a tradeoff. You make it more costly to crack than the information itself is worth.

Choose a good password (longer is better, mix letters and numbers) and set your Keychain to remember it.

Your Macintosh should have mounted the image. Copy the files you need to the image and unmount it.

Now you can carry the thumb drive around, and no one is going to get into your secure files without the password.

When you get to the other Macintosh, mount the image, enter the password (setting the Keychain to remember the password if you are going to do this again), and copy the files from the disk image to your desktop.

While we are on the subject of disk images, you can get better compression with a disk image than you can by archiving.

One more little trick. I've got a custom icon for my thumb drive. I keep a copy of the icon on the thumb drive just in case I need to put it on again.

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