101 research outputs found
Relativistic quantum coin tossing
A relativistic quantum information exchange protocol is proposed allowing two
distant users to realize ``coin tossing'' procedure. The protocol is based on
the point that in relativistic quantum theory reliable distinguishing between
the two orthogonal states generally requires a finite time depending on the
structure of these states.Comment: 6 pages, no figure
The cryptographic power of misaligned reference frames
Suppose that Alice and Bob define their coordinate axes differently, and the
change of reference frame between them is given by a probability distribution
mu over SO(3). We show that this uncertainty of reference frame is of no use
for bit commitment when mu is uniformly distributed over a (sub)group of SO(3),
but other choices of mu can give rise to a partially or even asymptotically
secure bit commitment.Comment: 4 pages Latex; v2 has a new referenc
Brief History of Quantum Cryptography: A Personal Perspective
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.Comment: 14 pages, no figure
Experimental quantum tossing of a single coin
The cryptographic protocol of coin tossing consists of two parties, Alice and
Bob, that do not trust each other, but want to generate a random bit. If the
parties use a classical communication channel and have unlimited computational
resources, one of them can always cheat perfectly. Here we analyze in detail
how the performance of a quantum coin tossing experiment should be compared to
classical protocols, taking into account the inevitable experimental
imperfections. We then report an all-optical fiber experiment in which a single
coin is tossed whose randomness is higher than achievable by any classical
protocol and present some easily realisable cheating strategies by Alice and
Bob.Comment: 13 page
A Private Quantum Bit String Commitment
We propose an entanglement-based quantum bit string commitment protocol whose
composability is proven in the random oracle model. This protocol has the
additional property of preserving the privacy of the committed message. Even
though this property is not resilient against man-in-the-middle attacks, this
threat can be circumvented by considering that the parties communicate through
an authenticated channel. The protocol remains secure (but not private) if we
realize the random oracles as physical unclonable functions in the so-called
bad PUF model with access before the opening phase.Comment: 8 pages, 4 figure
Analysis of one quantum bit string commitment
A. Kent proposed a quantum bit string commitment protocol in 2003.
Not using the standard two conjugate states , , and , the protocol uses
and , where . In this paper, we show that the
protocol can not guarantee security to the receiver.
bits are definitely exposed to the
receiver, where is the length of the committed string
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