This application was developed in collaboration between the Vilnius Gediminas Technical University (prof. Raimondas Čiegis, dr. Vadimas Starikovičius) and Kaunas University of Technology (prof. Minvydas Ragulskis, dr. Rita Palivonaitė).
Our colleagues from KTU are developing methods of chaotic dynamic visual cryptography and image hiding techniques based on moiré interference effects. See references (, ) for more information on their research.
Visual cryptography  is a cryptographic technique which allows the visual information to be encrypted in such a way that the decryption can be performed by the human visual system, i.e. without any cryptographic computation (see the example). This concept was introduced by Naor and Shamir  in 1994 and it gained a significant popularity due to a number of important applications [3,4].
The classical visual cryptography is based on the static superposition of several slides-shares. Dynamic visual cryptography and image hiding methods developed by our colleagues are generating only one encrypted image . The secret image can be seen by a human visual system only when the encrypted image is harmonically oscillated in a predefined direction at strictly defined amplitude of oscillation. See this video example and use pause to check the encrypted image, which is oscillated.
Seeking to improve the quality of the method, our colleagues from KTU are formulating discrete optimization problems to tune the method’s parameters. However, finding the optimal solution – set of parameters is practically impossible due to the fast-growing computational size of the problem.
To assist them in their research, we (scientists from VGTU) have developed parallel and distributed solvers of considered discrete optimization problem. Full search and several heuristic algorithms are implemented. These solvers and their performance (including results obtained by this project) are presented in our joint paper:
R. Čiegis, V. Starikovičius, N. Tumanova, M. Ragulskis. Application of distributed parallel computing for dynamic visual cryptography // The Journal of Supercomputing. New York: Springer Science+Business Media. ISSN 0920-8542. Vol. 72, iss., pp. 4204-4220, 2016. Link.
2. M. Naor and A. Shamir. Visual cryptography. Advances in cryptology. Eurocrypt ’94 Proceeding LNCS, 950, pp. 1–12, 1995.
3. C. Hegde, S. Manu, P.D. Shenoy, K. Venugopal, L. Patnaik. Secure authentication using image processing and visual cryptography for banking applications. In: ADCOM 2008. 16th international conference on advanced computing and communications, IEEE, pp. 65–72, 2008.
4. A. Ross, A. Othman. Visual cryptography for biometric privacy. IEEE Transactions on Information Forensics and Security 6(1), pp. 70–81, 2011.
5. M. Ragulskis and A. Aleksa. Image hiding based on time-averaging moiré. Optics Communications 282(14), pp. 2752–2759, 2009.
6. V. Petrauskienė. Dynamic visual cryptography based on non-linear oscillations. PhD thesis, Kaunas University of Technology, 2015. Link.