Table 4 Correlation coefficients of the original volume (\(r_{xy}\)) and the corresponding ciphered volume (\(\tilde{r}_{xy}\)); (v), (h) and (d) are related to vertical, horizontal and diagonal adjacency respectively

\(r_{xy} (v)\)

\(\tilde{r}_{xy} (v)\)

\(r_{xy} (h)\)

\(\tilde{r}_{xy} (h)\)

\(r_{xy} (d)\)

\(\tilde{r}_{xy} (d)\)