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Security against eavesdropping in quantum cryptography
In this article we deal with the security of the BB84 quantum cryptography
protocol over noisy channels using generalized privacy amplification. For this
we estimate the fraction of bits needed to be discarded during the privacy
amplification step. This estimate is given for two scenarios, both of which
assume the eavesdropper to access each of the signals independently and take
error correction into account. One scenario does not allow a delay of the
eavesdropper's measurement of a measurement probe until he receives additional
classical information. In this scenario we achieve a sharp bound. The other
scenario allows a measurement delay, so that the general attack of an
eavesdropper on individual signals is covered. This bound is not sharp but
allows a practical implementation of the protocol.Comment: 11 pages including 3 figures, contains new results not contained in
my Phys. Rev. A pape