Security firm Aladdin Knowledge Systems thinks it has found two great tastes that go good together, recently snagging a patent for a combination smart card / optical disc. Dubbed the "XCD" (for Extended, not Xtreme, alas), the technology embeds the smart card chip on the surface of the disc, along with a foldable or detachable USB (or FireWire) connector to connect the disc to a PC or other device. The idea, apart from the just-for-the-heck-of-it factor, is to use the smart card functionality to control access to data on the disc -- for instance, limiting the number of times a CD can be played. Not surprisingly, Aladdin sees virtually limitless potential for the device, with XCDs able to replace ATM cards, credit cards, ID cards, and key cards, with the disc even able to fold up and fit in your wallet. Let's just hope they've also got a patent for super-durable CDs.