Cryptography Reference
In-Depth Information
results from any two out of them are nothing but random pictures, where
R 1 R 2 R 3 reveals H, and consequently G. We realize that fR 1 ;R 2 ;R 3 g is
a set of VCRG-3 with respect to G.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
(i)
FIGURE 7.7
Results of Algorithm 7 where Encryption VCRG (H, 3) was implemented by
Algorithm 4 with respect to gray-level image G in Experiment 2: (a) G; (b)
halftone version H of G; (c) R 1 , (d) R 2 , (e) R 3 ; (f) R 1 R 2 , (g) R 1 R 3 , (h)
R 2 R 3 ; (i) R 1 R 2 R 3 .
Let fR 1 ;R 2 ;R 3 g and fR 1 ;R 2 ;R 3 g denote the outcomes of Algorithm 7
when Encryption VCRG (H, 3) was implemented by Algorithms 5 and 6, re-
spectively, with respect to G. Figures 7.8(a) and (b) are the superimposed
results of R 1 R 2 R 3 and R 1 R 2 R 3 , respectively. It is noted that the
three encrypted shares and the superimposed result of any group of two out
of the three shares are indeed random grids that are omitted here.
The feasibility and applicability for Algorithm 7 to encrypt a gray-level
image into VCRG-3 are demonstrated in a visual sense from Figures 7.7 and
7.8. Obviously, implementing Encryption VCRG (H, 3) based upon Algorithm
4 makes Algorithm 7 achieve the highest contrast (while that based upon Al-
gorithm 5 is the worst).
Experiment 3: Encrypting a color image to obtain color VCRG-3.
We tested Algorithm 8 with respect to a color image for obtaining color
VCRG-3 in this experiment. Figure 7.9(a) is the color image P to be en-
crypted; (b), (c), and (d) are P c , P m , and P y , which are the c, m, and y
 
 
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