# Novel Algorithm for Multi-Time Data Implantation in a Special Cyber-Manufacturing Architecture
## 2 Background Study
### Related Study on Data Security  
Cryptography is a traditional method of managing the secrecy of the message. In cryptography, an encryption technique destroys the meaning of the data. The sender side does it at its end using a suitable key. The secret key helps the communicating parties to decrypt the modified data at the retriever end [12]. A smart technique of present data communication is to hide the secret message in a media, e.g., image, audio, video. The processes of hiding data in media are classified as watermarking and steganography. Watermarking is mainly used to provide data integrity, rather than security [13; 14; 15]. On the contrary, steganography is the art of hiding message data in a cover medium for securing a data communication method. A steganography method modifies the cover medium by some rules while implanting the secret message in it. The modified medium then called stego media. The steganography process makes the data invisible in the stego medium and thus, one cannot realize the existence of a secret in it while the stego medium is stolen. In fact, the system attains the ability of deceiving unauthorized person or devices pretending that there is nothing more inside the media. Therefore, the interest from both the data handler and the number of researchers is increasing in the field of steganography. Steganography schemes are broadly classified into two groups--reversible and irreversible. Reversible schemes retrieve both data and cover media at the extractor end without taking any help from the encoder module [9; 16; 17; 18; 19; 20; 21; 22; 23; 24]. On the other hand, irreversible schemes only extract secret data from the stego contents [8; 25; 26; 27; 28; 29]. These schemes are not concerned with rebuilding the cover media. Although image, audio and video are famous media for steganography, recently, some researchers have used a deoxyribonucleic acid (DNA) sequence in the cloud as a medium of hiding secrets [30; 31]. DNA sequences are available at various repositories. A very renowned one is NCBI [7; 30; 31]. [PERSON] et al. [30] and [PERSON] et al. [31] implanted secret bits in DNA. In 2019, the authors in [30] stated a DNA data hiding approach for data authenticity in mobile cloud. The cloud was based on the healthcare system. The authors used a cover DNA sequence with nucleotides A, C, G, T of length \(l\). They implanted a message \(M\) of \(n\)-bits. They converted the DNA sequence into a 2D matrix with \(n\) rows and \(l/n\) columns. They randomly calculated a one-time string \(E\) of \(n\)-bits. That \(E\) was a secret key. The method divides both \(M\) and \(E\) in \(\sigma\) segments with \(b\)-bits each, where \(\sigma=n/b\) and \(2\leq b\leq l/n\). They also used a substitution rule (SR), presented in Table 1, where they used '00' for nucleotide 'A', '01' for 'C', '10' for 'G' and '11' for 'T'. The position of a nucleotide in a 2D matrix was selected randomly using a sequence generator. The column sequence was stored in a set of named payload (R). Then, the method substitutes a pointed nucleotides by mapping binary values of the SR table, i.e., Table 1. That substitution mechanism produced a codeword \(W_{s}\) of length of \(b\)-bits. After that, \(\overline{W}_{s}\) were generated by the exclusive OR operation between message segment \(M_{s}\), codeword \(W_{s}\), and string segment \(E_{s}\). The \(\overline{W}_{s}\) was converted into nucleotides according to the SR. A 2D matrix was generated after repeating the aforementioned process and this 2D matrix was transformed into one-dimensional vector of nucleotides. Finally, it appended the payload \(R\) and tail \(T\) with the one-dimensional vector to construct the stego DNA sequence \(\overline{C}\). The stego DNA sequence \(\overline{C}\) and a stego key SK are sent to the cloud, where the stego key contains \(l,M,E,b\), SR and a seed for generating a pseudo-random sequence. The length of \(C\) was less than the length of \(\overline{C}\). [PERSON] et al.