It has been recently shown by Mayers that no bit commitment is secure if the participants have unlimited computational power and technology. However it was noticed that a secure protocol could be obtained by forcing the cheater to execute a measurement. Similar situations had been encountered previously in the design of Quantum Oblivious Transfer. The question is whether a classical bit commitment could be used for this specific purpose. We demonstrate that, surprisingly, classical unconditionally concealing bit commitments do not help.

. We consider a situation where two parties, Alice and Bob, share a common secret string and would like to mutually check their knowledge of that string. We describe a simple and e#cient protocol based on oblivious transfer to check mutual knowledge of a common string in such a way that honest parties will always succeed in convincing each other, while a dishonest party interacting with an honest party will have vanishingly small probability of convincing him. Moreover, a dishonest party gains only a very small amount of information about the secret string from running the protocol: whoever enters the protocol with no knowledge of the secret string would have to enter this protocol an exponential number of times in order to gain non-negligible information about the string. 1 Introduction Didn't you worry last time you typed your PIN (Personal Identification Number) to an unknown Automated Teller Machine (ATM) that it could be a fake and that the sole purpose of this ATM could be t...

The desire to obtain an unconditionally secure bit commitment protocol in quantum cryptography was expressed for the first time thirteen years ago. Bit commitment is sufficient 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 flaw 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.

The fates of SIGACT News and Quantum Cryptography are inseparably entangled. The exact date of Stephen Wiesner's invention of "conjugate coding" is unknown but it cannot be far from April 1969, when the premier issue of SIGACT News---or rather SICACT News as it was known at the time---came out. Much later, it was in SIGACT News that Wiesner's paper finally appeared [74] in the wake of the first author's early collaboration with Charles H. Bennett [7]. It was also in SIGACT News that the original experimental demonstration for quantum key distribution was announced for the first time [6] and that a thorough bibliography was published [19]. Finally, it was in SIGACT News that Doug Wiedemann chose to publish his discovery when he reinvented quantum key distribution in 1987, unaware of all previous work but Wiesner's [73, 5]. Most of the first decade of the history of quant