This chapter discusses one approach to the design of error-correction codes for the Gaussian wiretap channel. More specifically, we will consider one type of powerful error-correction codes called low-density parity-check (LDPC) codes and show how they should be designed to provide a high level of data security at the physical layer, which is left unsecured in conventional communication systems. After a short review of basic principles in physical layer security we proceed to show that well-performing codes for physical layer security can be designed by a technique called puncturing.