Resource allocation for the multi-carrier broadcast channel is well understood for a broad class of utility functions, under various quality-of-service constraints, and for different channel models. In this work, we also take security on the physical layer into account. We use the secrecy rate as the objective function for resource allocation and show the similarities and differences to the traditional power and sub-carrier allocations for sum capacity optimization. The sub-carrier selection is similar for both methods whereas the spectral power allocation shows different behavior. Finally, we demonstrate that rich multipath fading decreases the cost of security. All results are illustrated by numerical simulations and discussions.