ABSTRACT:VisualCryptography is an encryption technique where a secret image is cryptographically encoded into n meaningless share images. A basic model for visual cryptography for natural images was proposed by Naor and Shamir. Security has gained a lot of importance as information technology is widely used. Cryptography refers to the study of mathematical techniques and related aspects of Information Security like data confidentiality, data Integrity, and of data authentication. Visual cryptography is a process where a secret image is encrypted into shares which refuse to divulge information about the original secret image. Its strength is a fact that the decryption of the secret image is through human visual system without computation. This paper provides a formulation of encryption for multiple secret images, which is a generalization of the existing ones, and also a general method of constructing visual secret sharing schemes encrypting multiple secret images.

In VLSI technology the circuit has small size. The efficient size gained due to decreasing chip design to nano-scale. But as chip size becomes very less the factor which adversely affects the design is maintaining constant current in CMOS integrated circuit. Current mirror replicates input current at the output. There is need to design current mirror circuit such that it works efficiently with low power requirement. In this work the survey of different CM circuits analysed and studies. Each CM has its advantages, limitations and research gap which is noted and applicable for further development.

Current mirror is basic building block of amplifier, oscillator and comparator circuit. An ideal current mirror is independent of input power and temperature. The output current is constant mirrored image of input current. In order to avoid wrong equilibrium it must have high output impedance. This can be achieved by using super cascode formation. The single electron coulomb blockade structure provides low voltage operation and scaling of transistor to 10 nm. The Single Electron Transistor (SET) based CM is modeled and analyzed by simulation and the results shows improved performance of CM.

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