Making An Empty Promise With A Quantum Computer (Or, A Brief Review on the Impossibility of Quantum Bit Commitment)

The desire to obtain an unconditionally secure bit commitment protocol in quantum cryptography was expressed for the rst time thirteen years ago. Bit commitment is suucient in quantum cryptography to realize a variety of applications with unconditional security. In 1993, a quantum bit commitment protocol was proposed together with a security proof. However, a basic aw in the protocol was discovered by Mayers in 1995 and subsequently by Lo and Chau. Later the result was generalized by Mayers who showed that unconditionally secure bit commitment is impossible. A brief review on quantum bit commitment which focuses on the general impossibility theorem and on recent attempts to bypass this result is provided.