Due to their broadcast nature, wireless systems are vulnerable in the physical layer. While many physical layer security techniques are being developed, current security solutions are based on encryption techniques. This paper analyzes the relation between encryption techniques and physical layer security approaches and proposes a new encryption-aware multilayer security framework. The proposed framework optimizes transmit power by taking the adopted encryption technique into account, while guaranteeing both a quality of service (QoS) level for the legitimate receiver and a secrecy constraint against the eavesdropper. Numerical results are given for two most widely used symmetric encryption techniques, the data encryption (DES) and the advanced encryption (AES) standards. Numerical results show that the proposed encryption-aware physical layer security system achieves a better power efficiency when compared to the classical physical layer security approaches.