# Enhanced Joint and Separable Reversible Data Hiding in Encrypted Images with High Payload
## 5 Experimental Results and Discussion
### Joint System  
For joint data hiding system, as shown in Figure 9a, original test image Lena is encrypted to generate Figure 9b. Then, we embed 7225 bits (equivalent to a block size of 6 \(\times\) 6[15; 16; 17]) into the encrypted image by setting \(t\) = 5 and \(G\) = 15. After that, the image was decrypted as seen in Figure 9c. Finally, the hidden bits were successfully extracted and the original image was perfectly restored from the directly decrypted image as shown in Figure 9d. Figure 8: Test images used for the simulation (**a**) Lena; (**b**) Jet; (**c**) Peppers; and (**d**) Sailboat[24]. Figure 9: Experiment by joint system. (**a**) Original Lena; (**b**) encrypted Lena; (**c**) decrypted Lena containing information bits; and (**d**) recovered Lena. Tables 1-4 show the performance analysis of the proposed system for test images Lena, Jet, Peppers, and Sailboat, respectively. For the performance analysis, we consider bit error rate (BER) and embedding rate. The BER is the ratio of unrecovered bits to the total number of embedded bits, and the embedding rate is the ratio of the total embedded bits to the total pixels in the image. Figure 10 is a graphical representation of the bit error rate (%) versus data-embedding capacity (bits) for all the images. From the tables and Figure 10, we can see that the error rate increases with an increase in the embedding rate. If we embed more bits, then the error rate will also be higher. For the Lena image (Table 1 and Figure 10), when 16,384 bits (equivalent to a block size of \(4\times 4\)[15; 16; 17]) are embedded, that is the embedding rate is 0.0625, the error rate is 0; however, with 28,900 bits (equivalent to a block size of \(3\times 3\)[15; 16; 17]), the embedding rate is 0.11, and the error rate increases to 0.01. With the Jet image, as shown in Table 2 and Figure 10, when the embedding rate increases from 0.0275 to 0.0625, the error rate also rises from 0 to 0.04. Tables 3 and 4 also show similar results. Figure 10 also shows that the BER performance with the Lena image is better than the other images, since the spatial correlation of the Lena image is stronger than the other images. For Lena, 16,384 bits can be embedded error-free, whereas in the Jet and Pepper images, 7225 bits can be embedded error-free. On the other hand, the BER performance with Sailboat is worse than the other images because of weak spatial correlation. Therefore, the BER in the data hiding system depends on spatial correlation, too. Figures 11-14 show bit error rate comparisons between the proposed system and the referenced systems (based on embedded bits) for test images, Lena, Jet, Peppers, and Sailboat, respectively. In Figures 11a, 12a, 13a, and 14a, the difference between the proposed system and Wu and Sun [20] is small due to the scaling factor. So, we draw Figures 11b, 12b, 13b, and 14b, to compare the proposed system and Wu and Sun [20] and to indicate the difference clearly. For Lena, as shown in Figure 11, when 16,384 bits are embedded, the error rates for the [PERSON] [15], [PERSON] et al. [16], and [PERSON] et al. [17] systems are 15.8, 7.9, and 6.62%, respectively; whereas, the BER of the proposed system is 0, which is significantly lower than other systems. At 28,900 bits, the error rate for the [PERSON] and Sun system [20] is 0.04%, and the result of the proposed system is 0.01%, which is four times smaller than [PERSON] and [PERSON]'s. As seen in Figure 12, for the Jet image, the BER for [PERSON] [15], [PERSON] et al. [16], [PERSON] et al. [17], and Wu and Sun [20] systems are 18.6, 8.1, 7.2, and 0.24%, respectively; however, with the proposed system, the error rate is only 0.04%, which is significantly lower than the others. For the Peppers and Sailboat images, (Figures 13 and 14) the proposed system provides better performance than other systems. BER of the proposed scheme is almost equal to 0, since we divide the encrypted image into sets, instead of blocks; which helps to exploit the spatial correlation in natural images perfectly.