Quantum information theory is widely recognized as an arguably powerful paradigm for physically secure communications. In general, any attack that an eavesdropper, say Eve, perpetrates in order to gain access to messages or
keys exchanged by the legitimate parties, say Alice and Bob, will result in disturbances to quantum states that can
be detected with overwhelming probability — security is guaranteed by exploiting the fundamental laws of quantum
physics. Once a quantum channel is established, Alice and Bob can generate common randomness and use a mix
of public communication and privacy amplification to distill a secret key from the correlated random bit strings they
possess.