As technology is progressing and more and more personal data is digitized, there is even more need for data security today than there has ever been. Protecting this critical data in a secure way against the unauthorised access is an immensely difficult and complicated research problem. Within the cryptographic community, many attempts have been in this regard. In visual cryptography, secret sharing offers a similar scheme, where a secret S, encoded into an image is shared among a group of n members, each of them holds a portion of the secret as their secret shares. The secret can only be retrieved when a certain number of t members (where t ≤ n) combine their shares together. And while any combination with fewer than t shares have no extra information about the secret than 0 shares. This kind of secret sharing system is known as (t, n) threshold scheme or toutofn VC scheme. In this paper, we discuss various types of visual cryptographic schemes emphasizing on improving the efficiency and capacity of the original schemes. An analysis on the optimal contrast of the recovered secret, the robustness and security issues of technique is also presented. This paper attempts to develop a mathematical model based on interpolation for visual cryptography. Such a model using Lagrange’s formula is implemented and experimental results are verified.
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