  A new nonlinear Rao-Nam like symmetric key encryption scheme is presented in
this paper. QC-LDPC lattices that are practically implementable in high
dimensions due to their low complexity encoding and decoding algorithms, are
used in our design. Then, a joint scheme is proposed which is capable of
encrypting, encoding and data modulation simultaneously. The proposed
cryptosystem withstands all variants of chosen plaintext attacks applied on
Rao-Nam like cryptosystems due to its nonlinearity. The sparseness of the
parity-check matrix of QC-LDPC lattices, quasi-cyclic nature of their generator
and parity-check matrices, simple hardware structure for generating intentional
error vector, permutation and nonlinear functions, result in a small key size
for our scheme. The lattice codes related to the lattices used in this paper
have high rate which are suitable for bandlimited AWGN channels. Therefore, the
joint scheme based on these lattices facilitates secure, reliable and efficient
data transmission in bandlimited AWGN channels.
