René Ndoundam

Juvet K. Sadié, Leonel Moyou Metcheka, René Ndoundam

Text steganography is a mechanism of hiding secret text message inside another text as a covering message. In this paper, we propose a text steganographic scheme based on color coding. This include two different methods: the first based on permutation, and the second based on numeration systems. Given a secret message and a cover text, the proposed schemes embed the secret message in the cover text by making it colored. The stego-text is then sent to the receiver by mail. After experiments, the results obtained show that our models performs a better hiding process in terms of hiding capacity as compared to the scheme of Aruna Malik et al. in which our idea is based.

Rene Ndoundam, Stephane Gael R. Ekodeck

We propose a new model of steganography based on a list of pseudo-randomly sorted sequences of characters. Given a list $L$ of $m$ columns containing $n$ distinct strings each, with low or no semantic relationship between columns taken two by two, and a secret message $s \in \{0,1\}^*$, our model embeds $s$ in $L$ block by block, by generating, for each column of $L$, a permutation number and by reordering strings contained in it according to that number. Where, letting $l$ be average bit length of a string, the embedding capacity is given by $[(m-1)*log_2(n!-1)/n*l]$. We've shown that optimal efficiency of the method can be obtained with the condition that $(n >> l)$. The results which has been obtained by experiments, show that our model performs a better hiding process than some of the important existing methods, in terms of hiding capacity.

Fabrice P. Tachago, Stephane G. R. Ekodeck, Rene Ndoundam

Informally, steganography is the process of exchanging a secret message between two communicating entities so that an eavesdropper may not know that a message has been sent. After a review of some steganographic systems, we found that these systems have some defects. First, there are situations in which some concealment algorithms do not properly hide a secret message. Second, to conceal one bit of a secret message, some ask at least five documents and make at least two sampling operations, thus increasing their run-times. Considering the different ways to communicate with the receiver, we propose two steganographic systems adapted to the email communication whose algorithms are deterministic. To hide one bit of a secret message, our steganographic systems need only one document and performs one sampling operation and therefore significantly reduces the run-time.

Rene Ndoundam, Stephane Gael Raymond Ekodeck

We propose different approaches of PDF files based steganography, essentially based on the Chinese Remainder Theorem. Here, after a cover PDF document has been released from unnecessary A0, a secret message is hidden in it using one of the proposed approaches, making it invisible to common PDF readers, and the file is then transmitted through a non-secure communication channel. Where each of our methods, ensure the condition that the number of inserted A0 is less than the number of characters of the secret message s.

Serge Alain Ebélé, Renè Ndoundam

We characterize the structure of the periods of a neuronal recurrence equation. Firstly, we give a characterization of k-chains in 0-1 periodic sequences. Secondly, we characterize the periods of all cycles of some neuronal recurrence equation. Thirdly, we explain how these results can be used to deduce the existence of the generalized period-halving bifurcation.