USB flash drives are very small, very portable, very convenient -- and very easy to lose. In fact, the question to ask these days isn't how to avoid losing your flash drive, but how to make sure your data is safe when you do. As a result, Computerworld decided it was time to look at seven USB flash drives that are outfitted with security features to keep your data safe.

We did what most IT managers and users would do and asked some of the top vendors for their most secure USB flash drives. All but one of these products use some form of the Advanced Encryption Standard (AES) encryption, either 128-bit or 256-bit (according to experts, there's not much of a difference between 128-bit and 256-bit levels of AES encryption for ordinary purposes, as neither has yet been broken).

There was some variation in the implementation of the encryption on these drives -- some use AES keys derived from a user's password, while others use encryption keys generated by a hardware-based random number generator.

Our three reviewers -- Bill O'Brien, Rich Ericson and Lucas Mearian -- did not test the encryption algorithms themselves (that's a subject for another article), but did test the drives' performance, I/O rates, and CPU utilization. The reviewers also looked at the drives' security features, price, ease of installation, and ease of use.

Each device was tested for speed using Simpli Software's Hd Tach 3.0. Interestingly, the reviewers came up with a wider range of performance numbers than anyone actually expected.

In fact, this turned out to be a very diverse group of drives with features ranging from secure and unsecure data partitioning, to waterproof, stainless-steel cases, to support for passwords of up to 99 characters. In every instance, there are different levels of ingenuity that went into the creation of these handy, very mobile devices, even if the level of protection varies.

This is by no means the definitive list of all the drives available -- only some from the largest vendors and the most highly advertised. There are many types of secure USB drives out there, including those using fingerprint scanning technology (we'll visit those in a later review).

In choosing a secure USB flash drive, you may have to first decide the relative importance of security, price, and speed, and compromise among those three factors. But in the end, we found that one drive stands out above the others.