4.2 Extraction procedure

Like all the information hiding papers, only the receiver can extract the message. But it is worth pointing out the receiver only uses the stego image to extract the secret text in our scheme that means it is a blind scheme. The extracting procedure can be described as follows.


#### Advances in Quantum Communication and Information

Figure 10. Embedding circuit: (a) specific embedding block circuit and (b) the whole circuit.

#### 4.2.1 Extraction

As can be seen from the above, the eight bit-planes of the secret text can be extracted from the eight blocks of the stego image. Accordingly, we can consider one block as an example. If the position of the stego image and the auxiliary blank quantum text are equal, and GRAY S<sup>7</sup> YXS<sup>6</sup> YXS<sup>5</sup> YX � � is even and <sup>C</sup><sup>0</sup> YX ¼ 1 or GRAY S<sup>7</sup> YXS<sup>6</sup> YXS<sup>5</sup> YX � � is odd and <sup>C</sup><sup>0</sup> YX <sup>¼</sup> 0, then <sup>T</sup>^<sup>i</sup> � � � E ¼ j i1 . The corresponding circuit is shown in Figure 11a, and a whole extracting circuit that combines the extraction of all eight blocks together is exposed in Figure 11b.

Figure 11.

Figure 12. Inverse transform.

23

Extracting circuit: (a) specific extracting block circuit and (b) the whole circuit.

A Novel Quantum Steganography Scheme Based on ASCII

DOI: http://dx.doi.org/10.5772/intechopen.86413

#### 4.2.2 Descrambling

Due to the operators used in embedding process are unitary, for this step of extracting process, we can use the inverse transpose of operators used in the embedding process. Figure 12 affords the quantum circuit to extract the secret image j i <sup>T</sup> from <sup>T</sup>^ � � � .

A Novel Quantum Steganography Scheme Based on ASCII DOI: http://dx.doi.org/10.5772/intechopen.86413

Figure 12. Inverse transform.

4.2.1 Extraction

Figure 10.

GRAY S<sup>7</sup>

YXS<sup>6</sup> YXS<sup>5</sup> YX � � is odd and C<sup>0</sup>

4.2.2 Descrambling

image j i <sup>T</sup> from <sup>T</sup>^

22

� � � .

quantum text are equal, and GRAY S<sup>7</sup>

of all eight blocks together is exposed in Figure 11b.

Embedding circuit: (a) specific embedding block circuit and (b) the whole circuit.

Advances in Quantum Communication and Information

As can be seen from the above, the eight bit-planes of the secret text can be extracted from the eight blocks of the stego image. Accordingly, we can consider one block as an example. If the position of the stego image and the auxiliary blank

> YXS<sup>6</sup> YXS<sup>5</sup> YX � � is even and C<sup>0</sup>

YX <sup>¼</sup> 0, then <sup>T</sup>^<sup>i</sup> �

is shown in Figure 11a, and a whole extracting circuit that combines the extraction

Due to the operators used in embedding process are unitary, for this step of extracting process, we can use the inverse transpose of operators used in the embedding process. Figure 12 affords the quantum circuit to extract the secret

� � E YX ¼ 1 or

¼ j i1 . The corresponding circuit
