Bounds for Visual Cryptography Schemes

In this paper, we investigate the best pixel expansion of the various models of visual cryptography schemes. In this regard, we consider visual cryptography schemes introduced by Tzeng and Hu [13]. In such a model, only minimal qualified sets can recover the secret image and that the recovered secret image can be darker or lighter than the background. Blundo et al. [4] introduced a lower bound for the best pixel expansion of this scheme in terms of minimal qualified sets. We present another lower bound for the best pixel expansion of the scheme. As a corollary, we introduce a lower bound, based on an induced matching of hypergraph of qualified sets, for the best pixel expansion of the aforementioned model and the traditional model of visual cryptography realized by basis matrices. Finally, we study access structures based on graphs and we present an upper bound for the smallest pixel expansion in terms of strong chromatic index

PYTHON IMPLEMENTATION OF VISUAL SECRET SHARING SCHEMES

Visual secret sharing schemes (VSS) represent an important concept of visual cryptography. They permit the sharing of a secret image between multiple participants so that only authorized groups can recover the secret. This paper considers the software implementation of some black-and-white secret images VSS in Python programming language. PIL (Python Imaging Library) provides strong image processing capabilities, making the library suitable for this kind of implementation. We present samples of the results obtained from the software computation and draw some conclusions.visual secret sharing, visual cryptography, Python, PIL (Python Imaging Library)

KRIPTOGRAFI VISUAL PADA GAMBAR BERWARNA (RGB) MENGGUNAKAN ALGORITMA ELLIPTIC CURVE CRYPTOGRAPHY

ABSTRAK Kriptografi berperan penting pada era digital dalam mengamankan data dari peretas. Seiring berkembangnya teknologi, data yang dapat diamankan menggunakan kriptografi semakin luas, salah satunya adalah mengamankan gambar menggunakan kriptografi visual. Kriptografi visual merupakan kriptosistem yang memecah suatu gambar menjadi beberapa bagian dan hanya dapat dipecahkan jika memiliki semua bagian dari gambar tersebut. Jenis kriptografi lain yang dapat digunakan dalam mengamankan data adalah elliptic curve cryptography (ECC). ECC menggunakan suatu lapangan atas bilangan prima yang berisi titik-titik pada kurva eliptik sebagai teknik pengamanan datanya. Dalam penelitian ini dilakukan pengembangan kriptosistem dengan menggabungkan kriptografi visual dan ECC serta implementasinya dalam mengkonstruksi program aplikasi komputer menggunakan MATLAB R2014a. Pengembangan kriptografi visual menggunakan Elliptic Curve Cryptography dapat mempersulit kriptanalisis karena harus meretas dua algoritma dan tidak akan bisa diretas jika hanya memperoleh salah satu share image. Kata Kunci: Kriptografi, Kriptografi Visual, Elliptic Curve Cryptography.  ABSTRACT Cryptography held an important role in the digital era for securing data from hackers. As technology develops, types of data that can be secured using cryptography is expanding, one of which is securing images using visual cryptography. Visual cryptography is a cryptosystem that splits an image into parts and can only be solved if it has all parts of the image. Another type of cryptography that can be used to secure data is Elliptic Curve Cryptography (ECC). ECC uses a field of prime numbers consists of points on the elliptic curve as a technique to secure data. In this research, a cryptosystem development was carried out by visual cryptography combined with ECC and its implementation in constructing a computer application program using MATLAB R2014a. The development of visual cryptography using Elliptic Curve Cryptography can complicate cryptanalysis because it has two algorithms and cannot be hacked if only one share image was obtained. Keywords: Cryptography, Visual Cryptography, Elliptic Curve Cryptograph

A Recursive Threshold Visual Cryptography Scheme

This paper presents a recursive hiding scheme for 2 out of 3 secret sharing. In recursive hiding of secrets, the user encodes additional information about smaller secrets in the shares of a larger secret without an expansion in the size of the latter, thereby increasing the efficiency of secret sharing. We present applications of our proposed protocol to images as well as text.Comment: 8 page