1,718 research outputs found
On Real-valued Visual Cryptographic Basis Matrices
Visual cryptography (VC) encodes an image into noise-like shares, which can be stacked to reveal a reduced quality version of the original. The problem with encrypting colour images is that they must undergo heavy pre-processing to reduce them to binary, entailing significant quality loss. This paper proposes VC that works directly on intermediate grayscale values per colour channel and demonstrates real-valued basis matrices for this purpose. The resulting stacked shares produce a clearer reconstruction than in binary VC, and to the best of the authors’ knowledge, is the first method posing no restrictions on colour values
while maintaining the ability to decrypt with human vision. Grayscale and colour images of differing entropies are encrypted using fuzzy OR and XOR, and their PSNR and structural similarities are compared with binary VC to demonstrate improved quality. It is compared with previous research and its advantages highlighted, notably in high quality reconstructions with minimal processing
Acoustic Integrity Codes: Secure Device Pairing Using Short-Range Acoustic Communication
Secure Device Pairing (SDP) relies on an out-of-band channel to authenticate
devices. This requires a common hardware interface, which limits the use of
existing SDP systems. We propose to use short-range acoustic communication for
the initial pairing. Audio hardware is commonly available on existing
off-the-shelf devices and can be accessed from user space without requiring
firmware or hardware modifications. We improve upon previous approaches by
designing Acoustic Integrity Codes (AICs): a modulation scheme that provides
message authentication on the acoustic physical layer. We analyze their
security and demonstrate that we can defend against signal cancellation attacks
by designing signals with low autocorrelation. Our system can detect
overshadowing attacks using a ternary decision function with a threshold. In
our evaluation of this SDP scheme's security and robustness, we achieve a bit
error ratio below 0.1% for a net bit rate of 100 bps with a signal-to-noise
ratio (SNR) of 14 dB. Using our open-source proof-of-concept implementation on
Android smartphones, we demonstrate pairing between different smartphone
models.Comment: 11 pages, 11 figures. Published at ACM WiSec 2020 (13th ACM
Conference on Security and Privacy in Wireless and Mobile Networks). Updated
reference
Simultaneous Visual Cryptography
A visual cryptography scheme (VCS), as proposed by M. Naor and A. Shamir, encodes a secret image into n different shares. The scheme ensures that only certain designated combinations of shares can recover the original image, while other combinations yield, in probabilistic sense, no information about the secret image. In this thesis, we show that there exist simultaneous visual cryptography schemes (SVCS), i.e. cryptographic schemes that allow for multiple secret images to be encoded across a set of n shares. The essential part of this research is to derive a set of formal definitions used to construct a valid SVCS and to design and examine different approaches for establishing valid SVCS constructions. In particular, we describe an SVCS that allows encoding n 1 distinct secret images across a set of n shares, and include a program that demonstrates the successful use of this SVCS in the appendix
Two-out-of-two color matching based visual cryptography schemes
International audienceVisual cryptography which consists in sharing a secret message between transparencies has been extended to color prints. In this paper, we propose a new visual cryptography scheme based on color matching. The stacked printed media reveal a uniformly colored message decoded by the human visual system. In contrast with the previous color visual cryptography schemes, the proposed one enables to share images without pixel expansion and to detect a forgery as the color of the message is kept secret. In order to correctly print the colors on the media and to increase the security of the scheme, we use spectral models developed for color reproduction describing printed colors from an optical point of view
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