5.4. Security
Encrypting multimedia contents involves scrambling the multi- media data stream to guarantee secure transmission of the data
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stream in the client/server transaction. This procedure can be achieved using standard symmetric key cryptographic methods. These methods treat multimedia data stream as a binary stream and cipher the entire stream using a traditional cryptographic algorithm, such as AES (Stinson, 2006). In general, non-real-time applications can utilize the traditional encryption algorithms. How- ever, employing standard encryption protocols for the encryption of the complete multimedia data stream is reflected as a naive approach (Agi & Gong, 1996). A range of limitations exists in the case of multimedia-enabled mobile applications, thereby making such schemes impractical. For example, the available computa- tional resources combined with limited battery life in mobile devices limit the application of AES-like encryptions. Furthermore, encrypting the transmission of multimedia content is beyond the application of the conventional encryption techniques primarily because of the way multimedia is utilized in contrast to textual data. Unlike data encryption, multimedia encryption on mobile device opens various challenging opportunities because the mobile subscribers will not wait for encryption and authentication. There- fore, a secure and real-time streaming of multimedia contents is a serious challenge for mobile multimedia delivery. Judiciously comparing the cost of the protection itself and the cost of the multi- media information requiring protection is necessary to identify an optimal security level for multimedia contents (Pande & Zambreno, 2011).