  In this paper, the performance of a secure massive multiple-input
multiple-output (MIMO) system adopting low-resolution digital-to-analog
converters (DACs) is analyzed over spatially correlated wireless channels. A
tight lower bound for the achievable secrecy rate is derived with artificial
noise (AN) transmitted in the null space of the user channels. Using the
analytical results, the impact of spatial correlation on the secrecy rate is
explicitly evaluated in the presence of low-resolution DACs. The analytical
observations reveal that using low-resolution DACs can be beneficial to the
secrecy performance compared with ideal DACs, when the channels are strongly
correlated and optimal power allocation is not employed.
