XOR-Based Visual Cryptography - Visual Cryptography and Secret Image Sharing - page 175

sharing scheme was applied to deal with gray scale and color secret images
respectively in Reference [22].

6.5.3 (k,n) Scheme
Based on above Wang et al.'s [23] (n;n) secret sharing scheme [23], Chao
and Lin [5] have attempted to construct a (k;n) secret sharing scheme. To
design a threshold (k;n) scheme, one may rst directly utilize Wang et al.'s

n
k 1

[23] (m;m) scheme for some carefully chosen parameter m = . The

(k;n;m) shadows-assignment matrix has n rows and m columns. Its n rows
represent n persons; and its m columns represent the m (distinct) temporary
shadows produced by the above (m;m) scheme. The element of H is either
0 or 1. The i-th person (row) has a copy of the j-th shadow image (column)
if and only if H ij . Each column of H have exactly k 1 zeros and nk + 1
ones.
Now we will introduce Chao et al.'s (k;n)-VC scheme based on the (k;n;m)
shadows assignment matrix H.