Threshold Schemes with Minimum Pixel Expansion

Definition

In visual secrete sharing schemes, attempts have been made to restrict the pixel expansion while images with high contrast are produced.

Although results obtained via a (k,n)-visual secret sharing (VSS) scheme can be easily revealed by a human observer without any computations, the size of shares is usually much larger compared to the size of the original input image. By encrypting the secret pixel into m ₁ m ₂ blocks of share pixels, the expansion is determined by the so-called expansion factor m ₁ m ₂ which denotes the number of columns of the n × m ₁ m ₂ basis matrices. In the recent past, attempts have been made to restrict the pixel expansion while images with high contrast are produced. The designer most often has to trade pixel expansion constraints to the recovered image quality and/or the order of (k,n)-threshold schemes [1–3].

A probabilistic VSS scheme which offers no pixel expansion (m ₁ m ₂= 1) which can be regarded as a VSS scheme with the minimum pixel...