  Correlations of the type discussed by EPR in their original 1935 paradox for
continuous variables exist for the quadrature phase amplitudes of two spatially
separated fields. These correlations were experimentally reported in 1992. We
propose to use such EPR beams in quantum cryptography, to transmit with high
efficiency messages in such a way that the receiver and sender may later
determine whether eavesdropping has occurred. The merit of the new proposal is
in the possibility of transmitting a reasonably secure yet predetermined key.
This would allow relay of a cryptographic key over long distances in the
presence of lossy channels.
