  We study the covert communication over K-user discrete memoryless
interference channels (DM-ICs) with a warden. It is assumed that the warden's
channel output distribution induced by K "off" input symbols, which are sent
when no communication occurs, is not a convex combination of those induced by
any other combination of input symbols (otherwise, the square-root law does not
hold). We derive the exact covert capacity region and show that a simple
point-to-point based scheme with treating interference as noise is optimal. In
addition, we analyze the secret key length required for the reliable and covert
communication with the desired rates, and present a channel condition where a
secret key between each user pair is unnecessary. The results are extended to
the Gaussian case and the case with multiple wardens.
