Audio steganography allows and inspires many researchers to design methods for secure communication. Based on the evaluation on the existing methods, it was found that most methods focused on one or two requirements while disregarding others, causing imbalanced performance. Moreover, most methods lack adaptivity and dynamic allocation. Therefore, in this research, a method called Adaptive Multi-level Phase Coding (AMPC) was proposed to optimize the above issues. The reverse logic of the main tradeoffs was used to empirically design several embedding levels that that simultaneously attained good performance for all aspects as much as possible. Then, an adaptive component was added by selecting the embedding level that provided the best performance for each embedding process. Moreover, the error spreading factor was introduced to achieve a fair payload distribution. The performance balance objective requires a new formulation that will enable the accurate selection of the degree of modification, multiple-bit embedding per modification, and reduced retrieval errors. As a result, the interval centering quantization (ICQ) was formulated and implemented in the proposed method. The experimental results show that AMPC successfully fulfilled the research objectives. Also, AMPC surpassed other phase coding methods in all aspects while time-domain methods achieved the highest transparency and capacity with the lowest robustness. Moreover, experiments show that the implementation of adaptive multi-level concept is able to improve the existing method's performance significantly. In summary, AMPC was able to achieve a stable embedding rate of 33 Kbps at 35 dB of SNR, which is higher than the recorded embedding rate of other phase coding methods.

Audio steganography refers to hiding a secret message inside a cover audio file. The existing methods follow almost a sequential embedding which leads to poor utilization of the cover. The proposed method aims to achieve the maximum feasible capacity of the audio file without lowering the quality. The proposed method is based on seven levels of thresholds and six LSB layers, while the embedding is carried out progressively. The method allocates the message bits over the cover signal horizontally to ensure fair payload distribution over the signal. Hence, the selected samples might be visited multiple times till the message is totally embedded. The experimental results show that the method is able to reach a hiding capacity of 40% of the file size or 266.6 kbps while maintaining an SNR and PSNR values of 40 and 58 dB respectively. It is concluded that the proposed progressive method is highly adaptive to the message size and capable of providing high-quality stego even when big payloads are used. The comparative study shows that the progressive method provides the best message distribution based on the nature of the cover.

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Network survivability analysis in MANETs was hardly an issue in the early years of wireless technology because there were no critical network system that depended on wireless technology yet. Today, network survivability analysis is an essential aspect of reliable communication especially in MANETs. Although various methods have been proposed to measure network survivability analysis in MANETs, no related review has been published as to date for this topic. Thus, a comprehensive review of this body of work would be beneficial to researchers to have an overview of the current state of research trend in this area. This paper provides a systematic literature review (SLR) of the state of the art approach in network survivability analysis in MANETs. We used studies from a number of relevant article sources, and our results showed the existence of twenty six (26) articles. From this SLR we found that the existing of analysis method is focusing on individual node in which the node is treated as independent event. Furthermore, the analysis also reveals the less popular methods in analyzing network survivability are with statistical methods such as regression analysis and survival analysis. The implication of this study is to give a clear direction to future researchers in this area for a better and accurate analysis in measuring network survivability in MANETs.

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