  We consider secure communication over a two-user Gaussian interference
channel, where each transmitter sends a confidential message to its legitimate
receiver. For this setting, we identify a regime where the simple scheme of
using Gaussian wiretap codebook at each transmitter (without cooperative
jamming) and treating interference as noise at each intended receiver (in
short, GWC-TIN scheme) achieves the optimal secure sum capacity to within a
constant gap. The results are proved by first considering the deterministic
interference channel model and identifying a regime in which a simple scheme
without using cooperative jamming is optimal in terms of secure sum capacity.
For the symmetric case of the deterministic model, this simple scheme is
optimal if and only if the interference-to-signal ratio (in channel strengths)
is no more than 2/3.
