Cryptography Reference
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Fig. 4.10. The diagram of the (2,2)-VSS bit plane reconstruction process.
After all sub-shadows were decrypted, the scheme reconstructed the binary
plane P j by composing T 1 , T 2 ,, T 2 k . Finally, the scheme stacks the obtained
planes to reconstruct the gray-scale image. The secret images, then, can be
seen by human vision.
4.3.4 The Decryption Example
Using the example as shown in Section 4.3.2, the shadows S 1 and S 2 are shown
in Fig. 4.9(g) and Fig. 4.9(h), respectively. Before starting the decryption
process, each shadow is decomposed into eight planes. The first two planes α 1
and β 1 for S 1 and S 2 are the same as Fig. 4.9(e) and Fig. 4.9(f), respectively.
Because the legal participants own the secret keys used to generate the original
random sequences, RA 1 =(3214)andRB 1 = (1 4 3 2), the scheme can
restore the sub-shadows of α 1 and β 1 into their original locations. The first
element of RA 1 is 3, which means the first sub-shadow a 1 is reversed to become
a 3 . Therefore, we change the sub-shadow a 3 into its original location 1. The
second element of RB 1 is 4, which means the second sub-shadow b 2 is reversed
to b 4 . We change the sub-shadow b 4 into its original location 2. The restored
shadows are the same as those in Fig. 4.9(c) and Fig. 4.9(d).
The scheme next uses the decryption function to reconstruct the original
binary plane. The first blocks of a 1 and b 1 are
10
10
01
01
and
, both of which
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