## 3 Proposed LAO-3D Block Cipher
### Encryption Algorithm
Any

\begin{table}
\begin{tabular}{c c c} \hline \hline
**Key** & **Plaintext** & **Ciphertext** \\ \hline
000000000000000000000000 & 00000000000000 & 5R0785 CAE521 FE7 \\FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF & 0000000000000000000 & 11F40B91480C2776 \\
65 CA1E79 BQ3 DF421A4C6F392 DB7508E & 000000000000000000 & 217B3379252P4976 \\
000000000000000000000000000000000000 &FFFFFFFFFFFFFFFFFFFF & 14741B345A2729D2 \\



encryption algorithm should provide both confusion and diffusion properties to ensure information security. Confusion is obtained through substitution; meanwhile, diffusion is achieved with permutation operations. Confusion and diffusion will produce a certain randomness degree in the block cipher such that no ciphertext pattern can be recognized. To evaluate the confusion and diffusion properties, three analyses were executed on the proposed block cipher--the correlation coefficient, bit error, and key sensitivity tests. In addition, a randomness evaluation was performed to examine the randomness characteristics of the algorithm. Finally, two cryptanalysis attacks were carried out to observe the strength of the LAO-3D block cipher. Apart from the security analysis, a performance test was conducted to measure the speed, throughput, and required cycles per byte to execute the encryption. For benchmarking purposes, the experimental results were compared with existing lightweight block ciphers, such as GIFT, KATAN, KLEIN, LED, LRBC, PRESENT, PRINCE, PRINT, QTL, RECTANGLE, SIMECK, SPECK, and TEA. These algorithms were chosen because of their similarity in terms of block and key sizes that were no bigger than 64 bits and 128 bits, respectively, to distinguish their security strengths and performances within the same lightweight category. In order to demonstrate the implementation of the LAO-3D lightweight block cipher, a mobile encryption application was developed to observe the functionality of the proposed algorithm. The application was built using C++ programming on Microsoft Visual Studio 2008 and Android Studio development software. ### Correlation Coefficient Test

The avalanche effect examines the non-linear properties of a cipher. A non-linear transformation provides a confusion characteristic that relies on the generated output from a particular input data. The correlation coefficient, bit error, and key sensitivity experiments were carried out to monitor the avalanche effect of the block cipher. For the sample generation, a pseudorandom bit generator was used to produce the keys and plaintexts. The avalanche effect, \(AE\), is defined in the following equation. Figure 8:0

where \(s\) is the plaintext/ciphertext length, while \(p_{i}\) and \(c_{i}\) are the \(i^{th}\) positions of the plaintext and ciphertext bits for \(i=(0,\ldots,63)\). The correlation coefficient analyzes the non-linear relationship between plaintext and ciphertext [28]. The correlation coefficient, \(R\), is able to discriminate the effect of confusion on the block cipher. The coefficient values range from \(-1\) to \(+1\), where the acceptable result ranges are shown in Figure 8:1

For the expression of the correlation coefficient, \(R\), refer to the following equation:

Figure 8:2 \begin{table}
\begin{tabular}{c c} \hline \hline
**Result** & **Correlation Potential** \\ \hline \(R=0\) & Non-linear relationship \\ \(0<R\leq 0.3\) or \(-0.3\leq R<0\) & Weak positive/negative linear relationship \\ \(0.3<R<0.7\) or \(-0.7<R<-0.3\) & Moderate positive/negative linear relationship \\ \(0.7\leq R<1\) or \(-1<R\leq-0.7\) & Strong positive/negative linear relationship \\ \(R=1\) or \(R=-1\) & Perfect positive/negative linear relationship \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Correlation Coefficient Result Indications. where \(AE\) represents the avalanche effect from (6), \(p_{i}\) indicates the \(i^{th}\) plaintext bit, and \(c_{i}\) defines the \(i^{th}\) ciphertext bit for \(i=(0,\ldots,63)\). The correlation values from the analysis conducted on the plaintext and ciphertext were remarked.