An introduction to quantum cryptography

It is widely believed that devising an "unbreakable" cryptographic method is an impossible task. We are still on an age-old quest to find such a method, because virtually all previous attempts have failed. Cryptography was the art of outsmarting a human enemy; today it is concerned more with resisting attack by very powerful computers. Cryptosystems in common use today (e.g., DES, RSA, AES; see [20] for details) are designed to withstand attacks from current generation computers as much as possible. However, the constant increase in available computational power will make these systems more vulnerable to attack.