Cryptography Reference
In-Depth Information
More recently, another simple proof of the BB84, which employs results from
quantum communication complexity, has been provided by Ben-Or [4] and
a general proof based on bounds on the performance of quantum memories
has been proposed by Christandl et al. [30].
Let us also mention in passing that apart from the scenario that favors
Eve, i.e., Eve has access to quantum computers while Alice and Bob do not,
there are interesting connections regarding the criteria for the key distillation
in commensurate cases, i.e., when Alice, Bob, and Eve have access to the same
technology, be it classical or quantum [18,10,1].
1.9 Concluding Remarks
Quantum cryptography was discovered independently in the U.S. and Eu-
rope. The first one to propose it was Stephen Wiesner, then at Columbia Uni-
versity in New York, who, in the early 1970s introduced the concept of quan-
tum conjugate coding [27]. He showed how to store or transmit two messages
by encoding them in two “conjugate observables” such as linear and circular
polarization of light, so that either, but not both, of which may be received
and decoded. He illustrated his idea with a design of unforgeable bank notes.
A decade later, building upon this work, Charles H. Bennett of the IBM T. J.
Watson Research Center and Gilles Brassard of the Universite de Montreal,
proposed a method for secure communication based on Wiesner's conjugate
observables [5]. However, these ideas remained by and large unknown to
physicists and crytologists. In 1990, independently and initially unaware of
the earlier work, the current author, then a Ph.D. student at the University
of Oxford, discovered and developed a different approach to quantum cryp-
tography based on peculiar quantum correlations known as quantum entan-
glement [16]. Since then, quantum cryptography has evolved into a thriving
experimental area and is quickly becoming a commercial proposition.
This brief overview has only scratched the surface of the many activities
that are presently being pursued under the heading of quantum cryptogra-
phy. It is focused solely on the development of theoretical concepts that led
to creating unbreakable quantum ciphers. The experimental developments,
although equally fascinating, are left to the other contributors to this topic. I
have also omitted many interesting topics in quantum cryptography that go
beyond the key distribution problem. Let me stop here hoping that even the
simplest outline of quantum key distribution has enough interesting physics
to keep you entertained for a while.
References
1. A. Acin, N. Gisin, and V. Scarani, Security bounds in quantum cryptography
using d-level systems,
Quant. Inf. Comp.
, 3(6), 563-580, November 2003.
2. H. Aschauer and H.-J. Briegel, A security proof for quantum cryptography
based entirely on entanglement purification,
Phys. Rev. A
, 66, 032302, 2002.
3. J.S. Bell,
Physics
, 1, 195, 1964.
