Author, institution: Rita Palivonaitė, Kaunas University of Technology
Science area, field: Physical Sciences, Informatics
The Doctoral Dissertation is available at the library of Kaunas University of Technology (K. Donelaičio St. 20, Kaunas).
Scientific supervisor:
Prof. Dr. Habil. Minvydas Kazys RAGULSKIS (Kaunas University of Technology, Physical Sciences, Informatics – 09P).
Dissertation Defense Board of Informatics Science Field:
Prof. Dr. Habil. Rimantas BARAUSKAS (Kaunas University of Technology, Physical Sciences, Informatics – 09P) – chairman;
Prof. Dr. Habil. Raimondas ČIEGIS (Vilnius Gediminas Technical University, Physical Sciences, Informatics – 09P);
Prof. Dr. Habil. Gintautas DZEMYDA (Vilnius University, Physical Sciences, Informatics – 09P);
Prof. Dr. Gintaras PALUBECKIS (Kaunas University of Technology, Physical Sciences, Informatics – 09P);
Prof. Dr. Eligijus SAKALAUSKAS (Kaunas University of Technology, Physical Sciences, Informatics – 09P);
Prof. Dr. Jonas VALANTINAS (Kaunas University of Technology, Physical Sciences, Informatics – 09P).
Annotation:
Visual cryptography is a cryptographic technique which allows visual information to be encrypted in such a way that the decryption can be performed by the human visual system, without any cryptographic computation. Dynamic visual cryptography is an alternative image hiding method that is based not on the static superposition of shares, but on time-averaging geometric moiré. This method generates only one picture, and the secret image can be interpreted by human visual system only when the original encoded image is harmonically oscillated in a predefined direction at strictly defined amplitude of oscillation. Experimental implementations of dynamic visual cryptography require generation of harmonic oscillations. Unfortunately, a nonlinear system excited by harmonic oscillations could result into a chaotic response. Therefore, the concept of chaotic dynamic visual cryptography is an important problem both from the theoretical and practical points of view. The feasibility of chaotic dynamic visual cryptography is one of the main topics in this dissertation – theoretical relationships and computational experiments are derived and discussed in details. Dynamic visual cryptography scheme based on the deformations of the cover image and improved dynamic visual cryptography schemes with enhanced security are provided as well.
