Quantum cryptography is the only approach to privacy ever proposed that allows two parties (who do not share a long secret key ahead of time) to communicate with provably perfect secrecy under the nose of an eavesdropper endowed with unlimited computational power and whose technology is limited by nothing but the fundamental laws of nature. This essay provides a personal historical perspective on the field. For the sake of liveliness, the style is purposely that of a spontaneous after-dinner speech. It will be seen that the IEEE played a ubiquitous role in this tale. I. PREHISTORY The story begins in the early 1960's, when Stephen Wiesner and Charles Bennett were undergraduates together at Brandeis University. Having many common friends, they enjoyed talking with each other. Later, after Wiesner had gone to grad- uate school at Columbia and Bennett at Harvard, they kept in touch. In particular, the former payed frequent visits to the lat- ter's communal house in Boston. During one of those visits 1 in the late 60's or early 70's 2 , Wiesner told Bennett of his ideas for using mechanics to make banknotes that would be impossible to counterfeit according to the laws of nature, as well as a quantum multiplexing channel, which would allow one party to send two messages to another in a way that the receiving party could decide which message to read but only at the cost of destroying the other message irreversibly. 3
Quantum cryptography is the only approach to privacy ever proposed that allows two parties (who do not share a long secret key ahead of time) to communicate with provably perfect secrecy under the nose of an eavesdropper endowed with unlimited computational power and whose technology is limited by nothing but the fundamental laws of nature. This essay provides a personal historical perspective on the field. For the sake of liveliness, the style is purposely that of a spontaneous after-dinner speech. It will be seen that the IEEE played a ubiquitous role in this tale. I. PREHISTORY The story begins in the early 1960's, when Stephen Wiesner and Charles Bennett were undergraduates together at Brandeis University. Having many common friends, they enjoyed talking with each other. Later, after Wiesner had gone to grad- uate school at Columbia and Bennett at Harvard, they kept in touch. In particular, the former payed frequent visits to the lat- ter's communal house in Boston. During one of those visits 1 in the late 60's or early 70's 2 , Wiesner told Bennett of his ideas for using mechanics to make banknotes that would be impossible to counterfeit according to the laws of nature, as well as a quantum multiplexing channel, which would allow one party to send two messages to another in a way that the receiving party could decide which message to read but only at the cost of destroying the other message irreversibly. 3
Quantum cryptography is the only approach to privacy ever proposed that allows two parties (who do not share a long secret key ahead of time) to communicate with provably perfect secrecy under the nose of an eavesdropper endowed with unlimited computational power and whose technology is limited by nothing but the fundamental laws of nature. This essay provides a personal historical perspective on the field. For the sake of liveliness, the style is purposely that of a spontaneous after-dinner speech. It will be seen that the IEEE played a ubiquitous role in this tale
Quantum cryptography aims at solving the everlasting problem of unconditional security in private communication. Every time we send personal information over a telecom channel a sophisticate algorithm protect our privacy making our data unintelligible to unauthorized receivers. These protocols resulted from the long history of cryptography. The security of modern cryptographic systems is guaranteed by complexity: the computational power that would be needed for gaining info on the code key largely exceed available one. Security of actual crypto systems is not “by principle” but “practical”. On the contrary, quantum technology promises to make possible to realize provably secure protocols. Quantum cryptology exploits paradigmatic aspects of quantum mechanics, like superposition principle and uncertainty relations. In this contribution, after a brief historical introduction, we aim at giving a survey on the physical principles underlying the quantum approach to cryptography. Then, we analyze a possible continuous variable protocol.
The history of Quantum Computing and Quantum Cryptography starts with a friendship between Charles Bennett and Stephen Wiesner, two undergraduates at Brandeis University who toyed with ideas for sending information using quantum entanglement, and John Conway's Game of Life, which stimulated interest in cellular automata at MIT in the 1970s and started a generation of computer scientists wondering if the universe might be some massive computer running a simulation of reality. In 1974 MIT professor Ed Fredkin spent his yearlong sabbatical at Caltech, where he learned quantum physics from Richard Feynman while he taught Feynman about computer science. Returning to MIT, Fredkin's ideas developed into the philosophy of digital physics, which blossomed into the 1981 Conference on Physics and Computation at MIT. Feynman's keynote at the conference described how a computer based on quantum mechanics principles could compute physics simulations much faster than today's classical compu
During the Cold War, a revolutionary cryptographic method, quantum cryptography, emerged. Grounded in the laws of quantum physics, quantum cryptography ensures absolute security using quantum principles. Stephen Wiesner introduced the concept in 1983, but initially received little attention, as technology at the time did not allow the encryption method to be put into practice. The field of quantum cryptography began to take shape with the arrival of two more researchers, Giles Brassard and Charles Bennett. The development of quantum cryptography accelerated dramatically after Artur Ekert proposed the application of Bell’s theorem in this field. Afterwards, more researchers got involved and new theorems and applications were developed, leading the field to become a major subject at the forefront of physics research. This paper explores why quantum cryptography is exceptionally secure and the steps that brought this idea to practice. The paper looks into the intriguing concept of quantum cryptography and the stimulating stories surrounding its progress. From Stephen Wiesner’s original proposal through Brassard and Bennett’s persistent efforts to the exciting debates between Ekert and Brassard and Bennett. This paper highlights the significant milestones and achievements that have positioned quantum cryptography at the forefront of physics research.
The practical implementation of quantum information technologies requires, for the most part, highly advanced and currently experimental procedures. One exception is quantum cryptography, or quantum key distribution, which has been successfully demonstrated in many laboratories and has reached an advanced level of development. It will probably become the first commercial application of quantum information. In quantum key distribution, Alice and Bob exploit a quantum channel to create a secret shared key comprising a random string of binary digits. This key can then be used to protect a subsequent communication between them. The principal idea is that the secrecy of the key distribution is ensured by the laws of quantum physics. Proving security for practical communication systems is a challenging problem and requires techniques that are beyond the scope of this book. At a fundamental level, however, the ideas are simple and may readily be understood with the knowledge we have already acquired. Quantum cryptography is the latest idea in the long history of secure (and not so secure) communications and, if it is to develop, it will have to compete with existing technologies. For this reason we begin with a brief survey of the history and current state of the art in secure communications before turning to the possibilities offered by quantum communications. The history of cryptography is a long and fascinating one. As a consequence of the success or, more spectacularly, the failure of ciphers, wars have been fought, battles decided, kingdoms won, and heads lost. In the information age, ciphers and cryptosystems have become part of everyday life; we use them to protect our computers, to shop over the Internet, and to access our money via an ATM (automated teller machine). One of the oldest and simplest of all ciphers is the transposition or Caesarean cipher (attributed to Julius Caesar), in which the letters are shifted by a known (and secret) number of places in the alphabet. If the shift is 1, for example, then A is enciphered as B, B→C, · · ·, Y→Z, Z→A. A shift of five places leads us to make the replacements A→F, B→G, · · ·, Y→D, Z→E.
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!