Wen-Pinn Fang

Bio: Wen-Pinn Fang is an academic researcher from Yuanpei University. The author has contributed to research in topics: Secret sharing & Homomorphic secret sharing. The author has an hindex of 9, co-authored 42 publications receiving 438 citations. Previous affiliations of Wen-Pinn Fang include National Chiao Tung University.

Progressive viewing and sharing of sensitive images

Abstract: The paper proposes a progressive viewing method useful in sharing a sensitive image. As in visual cryptography, this method characterizes its ability to recover the image by stacking transparencies without any computation. However, the method balances the sensitivity and the daily-processing convenience of the image.

Visual cryptography with extra ability of hiding confidential data

Abstract: We present a two-in-one visual cryptography (VC) scheme that not only shares an image of moderate confidentiality between two noisy transparencies, but also hides in these two transparencies a more confidential text file describing the image. None of the transparencies alone can reveal anything about the image or text. Later, people can view the image by simply stacking the two transparencies; on the other hand, after certain simple computations, the more confidential text data can also be extracted. We also introduce an alternative version in which the decoding of both the image and text requires no computer.

Non-expansion Visual Secret Sharing in Reversible Style

Abstract: Summary This paper proposed a novel reversible visual secret sharing method. Without any computing, if we stack two transparencies directly, a secret image will appear. Stacking two transparencies after reversing one of transparencies, another secret image will unveil. Different from traditional reversible visual cryptography, the method not only has advantages but also will not have pixel expansion and code-book. Besides, the same idea can be extended to complex style visual cryptography.

Visual Cryptography in reversible style

Abstract: We proposed in this paper a brand new type of visual cryptography (VC), namely, the VC in reversible style. For any two given secret images, two corresponding transparencies S1 and S2, also known as shares, can be produced. Both transparencies look noisy. However, if we stack the front views of both transparencies, then the first secret image is unveiled. On the other hand, if we stack the front view of S1 with the back view (the turn-over) of S2, then the second secret image is unveiled.

A comprehensive study of visual cryptography

Abstract: Visual cryptography (VC) is a powerful technique that combines the notions of perfect ciphers and secret sharing in cryptography with that of raster graphics. VC takes a binary image (the secret) and divides it into two or more pieces known as shares. When the shares are printed on transparencies and then superimposed, the secret can be recovered. No computer participation is required, thus demonstrating one of the distinguishing features of VC. VC is a unique technique in the sense that the encrypted message can be decrypted directly by the human visual system (HVS). In this survey, we will summarize the latest developments of visual cryptography since its inception in 1994, introduce the main research topics in this area and outline the current problems and possible solutions. Directions and trends for future VC work shall also be examined along with possible VC applications.

Progressive Visual Cryptography With Unexpanded Shares

Abstract: The basic (k, n)-threshold visual cryptography (VC) scheme is to share a secret image with n participants. The secret image can be recovered while stacking k or more shares obtained; but we will get nothing if there are less than k pieces of shares being overlapped. On the contrary, progressive VC can be utilized to recover the secret image gradually by superimposing more and more shares. If we only have a few pieces of shares, we could get an outline of the secret image; by increasing the number of the shares being stacked, the details of the hidden information can be revealed progressively. Previous research, such as Jin in 2005, and Fang and Lin in 2006, were all based upon pixel-expansion, which not only causes the waste of storage space and transmission time but also gets a poor visual quality on the stacked image. Furthermore, Fang and Lin's research had a severe security problem that will disclose the secret information on each share. In this letter, we proposed a brand new sharing scheme of progressive VC to produce pixel-unexpanded shares. In our research, the possibility for either black or white pixels of the secret image to appear as black pixels on the shares is the same, which approximates to 1/n. Therefore, no one can obtain any hidden information from a single share, hence ensures the security. When superimposing k (sheets of share), the possibility for the white pixels being stacked into black pixels remains 1/n, while the possibility rises to k/n for the black pixels, which sharpens the contrast of the stacked image and the hidden information, therefore, become more and more obvious. After superimposing all of the shares, the contrast rises to (n-1)/n which is apparently better than the traditional ways that can only obtain 50% of contrast, consequently, a clearer recovered image can be achieved.