The core advantage of quantum computing -- the ability to compute for many possible outcomes at the same time and therefore crunch data much more quickly than classical computers -- also creates a problem for data security. Once the first high-powered quantum computers are functioning, they'll be able to quickly saw through many of our most common data encryption algorithms. But as it turns out, an obscure encryption code created in 1978 is resistant to all known methods of quantum attack.
Such asymmetric code can be tricky for a classical computer to figure out but quantum computers are well suited to such work. To take a simple example, say a message was encrypted using basic multiplication -- one number is multiplied by a number to get a third number. It's not so easy to look at the third number and quickly determine the two numbers that spawned it.