Cryptography Reference
In-Depth Information
Fig. 4.11.
Diagram of (t, n)-VSS shadow generation process for the binary plane
P
j
.
then combines the sub-shadows to form the shadows, S
j,1
,S
j,2
,,S
j,n
,for
the plane P
j
. The final shadows of the gray-scale image are expressed as
S
1
= S
1,1
2
7
+ S
2,1
2
6
++ S
7,1
2
1
+ S
8,1
,
S
2
= S
1,2
2
7
+ S
2,2
2
6
++ S
7,2
2
1
+ S
8,2
,
.
S
n
= S
1,n
2
7
+ S
2,n
2
6
++ S
7,n
2
1
+ S
8,n
.
4.4.2 The Decryption Process for the (T, N)-VSS Scheme
The scheme decomposes each shadow into eight planes. The reconstruction
process is then performed on those planes to reconstruct the original plane
P
j
, shown in Fig. 4.12.
In Fig. 4.12, each shadow is separated into 2
k
sub-shadows. The scheme
restores the sub-shadows, a
j,χ
1
, a
j,χ
2
,, and a
j,χ
2
k
, to their original locations,
a
j,χ
1
, a
j,χ
2
,,anda
j,χ
2
k
, where 1≤χ≤n. The scheme uses the generated n
random sequences to restore the original sub-region. Only legal participants
who own the secret keys can generate the sequences needed to rearrange the
locations of the sub-shadows.
The decryption function for the (t, n)-VSS scheme is next used to decrypt
the secret information. The scheme stacks the sub-shadows, a
j,χ
1
, a
j,χ
2
,,and
