Abstract
This paper presents a method for speech steganography using two levels of security: The first one related to the scrambling process, the second one related to the hiding process. The scrambling block uses a technique based on the ability of adaptation of speech signals to super-Gaussian signals. The security of this block relies on the value of the seed for generating the super-Gaussian signal. Once the speech signal has been scrambled, this is hidden in a non-sensitive speech signal. The hiding process is adaptive and controlled by the value of bits to hold ( B H ). Several tests were performed in order to quantify the influence of B H in the quality of the stego signal and the recovered message. When B H is equal to six, symmetry was found between the modified bits and unchanged bits, and therefore hiding capacity is 50%. In that case, the quality of the stego signal is 99.2% and of the recovered signal is 97.4%. On the other hand, it is concluded that without knowledge of the seed an intruder cannot reverse the scrambling process because all values of the seed are likely. With the above results, it can be affirmed that the proposed algorithm symmetrically considers both the quality of the signal (stego and recovered) as well as the hiding capacity, with a very large value of the key space.
Highlights
In the last decades, technological development has highly facilitated communication processes between users, allowing a free flow of information of any kind.in many cases, confidentiality of information can be a major factor to satisfy
If the voice signal is transformed through scrambling or encryption, and the result hides in a host signal, the final system will work with at least two levels of security
In the specific case of techniques applied to voice messages, there are works in the area of data hiding and in the area of data randomisation
Summary
Technological development has highly facilitated communication processes between users, allowing a free flow of information of any kind (i.e., text, image, audio, video, etc.).in many cases, confidentiality of information can be a major factor to satisfy. In the case of audio signals, with the purpose of preserving confidentiality, there are three solutions available for covert communication: (i) To encrypt transmitted information, (ii) to manipulate or alter content (scrambling), (iii) to transmit secret information within another signal. Even if the third party intercepts the information being transmitted, the secret content goes unnoticed. In the specific case of techniques applied to voice messages, there are works in the area of data hiding ( steganography) and in the area of data randomisation (scrambling). In both scenarios, the process can use a secret key to increase system security. The authorised user who has the correct secret key will be able to reverse the concealment process and to obtain the original voice message
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