25 years of quantum cryptography

Abstract

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work but Wiesner's [73, 5].Most of the first decade of the history of quantum cryptography consisted of this lone unpublished paper by Wiesner. Fortunately, Bennett was among the few initiates who knew of Wiesner's ideas directly from the horse's mouth. His meeting with the first author of this column in 1979 was the beginning of a most fruitful lifelong collaboration. It took us five more years to invent quantum key distribution [4], which is still today the best-known application of quantum mechanics to cryptography. The second author joined in slightly later, followed by a few others. But until the early 1990's, no more than a handful of people were involved in quantum cryptographic research. Since then, the field has taken off with a vengeance, starting with Artur K. Ekert's proposal to use quantum nonlocality for cryptographic purposes [33].The golden age started in earnest when Ekert organized the first international workshop on quantum cryptography in Broadway, England, in 1993. Since then, many conferences have been devoted at least partly to quantum cryptography, which has become a major international topic. The purpose of the aforementioned 1993 bibliography in SIGACT News was to cite as much as possible all papers ever written on the subject, including unpublished manuscripts: there were 57 entries in total. Today, such an undertaking would be nearly impossible owing to the explosion of new research in the field.The purpose of this column is to give an overview of the current research in quantum cryptography. It is not our intention to be exhaustive and we apologize in advance to any researcher whose work we may have omitted. Note that we do not necessarily agree with the claims in every paper mentioned here: this column should not be construed as a seal of approval!