Broadcast and multicast services in CDMA2000 wireless networks restrict the provision of high-quality multimedia services to their intended recipients by encrypting the content using the advanced encryption standard (AES) block cipher in the security layer of the broadcast protocol suite. We profile the execution time and the energy of each transformation within the AES decryption process and propose a novel analytic model for predicting the time and energy that are required to decrypt the content at a mobile receiver. The model uses the cross-layer information, including the characteristics of error control in the MAC layer and the varying conditions of the fading channel in the physical layer. In particular, we find that the decryption time varies significantly with the condition of the physical channel. Rate control is, therefore, required to smooth out these variations in the decryption time. For this purpose, we propose the introduction of a jitter buffer into the security layer and estimate the size of this jitter buffer to provide seamless multimedia services.