4.1.3 Embedding

4.1.1 Scrambling

Scrambling by Gray code transform.

Figure 8.

4.1.2 Partitioning

sized 2<sup>n</sup>�<sup>2</sup> � <sup>2</sup><sup>n</sup>�<sup>1</sup>

Figure 9.

20

An example of partition.

For purpose of improving the security of secret text, the text message of j i T will be scrambled by Gray code transform before the embedding procedure. As mentioned in Subsection 2.2, in the eight qubits which store the text message, seven CNOT gates are used according to Gray code transform method, while the qubits representing for position information are not changed by quantum gates, the

In the proposed scheme, the 2<sup>n</sup> � <sup>2</sup><sup>n</sup> cover image is divided into 4 � 2 blocks

. We define these blocks as Bij, where ji¼ <sup>i</sup> yn yn�<sup>1</sup>

are called control coordinates because if they are restricted as a specific value, then one of blocks will be selected. For example, if their values are equal to 00 j i and 0j i,

 

and j i¼ j j i xn

corresponding circuit is demonstrated in Figure 8.

Advances in Quantum Communication and Information

After dividing the cover image, the quantum equal (QE) circuit is used to compare the coordinates of a block and quantum text. Then, the stego image j iS is obtained after embedding process. More specifically, taking one of the blocks as an illustration, if the coordinates yn�<sup>3</sup>yn�4…y<sup>0</sup> � � � j i xn�<sup>2</sup>xn�3…x<sup>0</sup> of j i C is equal to the coordinates of T^ � � � , <sup>T</sup>^<sup>i</sup> � � � E is embedded in C<sup>0</sup> � � � by the following pseudo-code.

```
If T^i �
  �
  �
     E
       = 1j i
If GRAY C7
          YXC6
              YXC5
        YX � � is even
SWAP C0
      YX; 1 � �
Else if GRAY C7
               YXC6
                   YXC5
            YX � � is odd
SWAP C0
      YX; 0 � �
End
If T^i �
  �
  �
     E
       = 0j i
If GRAY C7
          YXC6
              YXC5
        YX � � is even
SWAP C0
      YX; 0 � �
Else if GRAY C7
               YXC6
                   YXC5
            YX � � is odd
SWAP C0
      YX; 1 � �
End
```
where the function GRAY ið Þ is the Gray code value of i, and the function SWAP ið Þ ; j is to swap the value of i and j. The corresponding embed block circuit is shown in Figure 10a and b presents the integrated embedding circuit that contains the selection of the block of cover image, the comparison of the coordinates, and the embedding process of the bit-planes of secret text into the LSB of cover image.
