  Although practised as an art and science for ages, cryptography had to wait
until the mid-twentieth century before Claude Shannon gave it a strong
mathematical foundation. However, Shannon's approach was rooted is his own
information theory, itself inspired by the classical physics of Newton and
Einstein. But our world is ruled by the laws of quantum mechanics. When
quantum-mechanical phenomena are taken into account, new vistas open up both
for codemakers and codebreakers. Is quantum mechanics a blessing or a curse for
the protection of privacy? As we shall see, the jury is still out!
