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Since many people consume multimedia content (music, movie etc.) on mobile devices, mobile DRM becomes important, which controls digital content usage under wireless environment. In a typical DRM model, a block cipher is usually used to encrypt multimedia content because of its reasonable security and performance. However, encrypting multimedia content using a block cipher in mobile environment requires much computation power and energy due to its huge size. It is critical problems because users want long playtime and quick responsiveness with random access. In this paper, we propose an efficient multimedia content encryption scheme for mobile handheld devices (EMCEM), which uses a block cipher to encrypt some parts of content and a stream cipher to encrypt the others. We also use different stream cipher key to improve security. EMCEM accommodates the current DRM architecture, supports random access to a media file, and has flexibility to determine easily the trade-off between performance and security. Experimental results have shown that EMCEM has much better performance than encrypting content completely using a block cipher.