  Continuous variable one-way and controlled-two-way secure direct quantum
communication schemes have been designed using Gaussian states. Specifically, a
scheme for continuous variable quantum secure direct communication and another
scheme for continuous variable controlled quantum dialogue are proposed using
single-mode squeezed coherent states. The security of the proposed schemes
against a set of attacks (e.g., Gaussian quantum cloning machine and intercept
resend attacks) has been proved. Further, it is established that the proposed
schemes do not require two-mode squeezed states which are essential for a set
of existing proposals. The controlled two-way communication scheme is shown to
be very general in nature as it can be reduced to schemes for various
relatively simpler cryptographic tasks like controlled deterministic secure
communication, quantum dialogue, quantum key distribution. In addition, it is
briefly discussed that the proposed schemes can provide us tools to design
quantum cryptographic solutions for several socioeconomic problems.
