Vulnerability to chosen-cyphertext attacks of optical encryption schemes based on double random phase keys

Universitat de Barcelona, Departament de Física Aplicada i Optica, Diagonal 647, 08028 Barcelona, Spain.
Optics Letters (Impact Factor: 3.29). 08/2005; 30(13):1644-6. DOI: 10.1364/OL.30.001644
Source: PubMed


We show how optical encryption methods based on double random phase keys are vulnerable to an organized attack of the chosen-ciphertext type. The decryption key can be easily obtained by an opponent who has repeated access to either the encryption or decryption machines. However, we have also devised a solution that prevents the attack. Our results cast doubts on the present security of these techniques.

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    • "For 512 Â 512 greyscale image with 256 possible phases per pixel, the number of keys to try is 256 524288 . However, it has been proved that under specific attacks, DPRE can be weak [9] [10] [11] [12] [13]. More specifically, DRPE is vulnerable for chosen-plaintext attack. "
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    ABSTRACT: The double random phase encryption (DRPE) method is a well-known all-optical architecture which has many advantages especially in terms of encryption efficiency. However, the method presents some vulnerabilities against attacks and requires a large quantity of information to encode the complex output plane. In this paper, we present an innovative hybrid technique to enhance the performance of DRPE method in terms of compression and encryption. An optimized simultaneous compression and encryption method is applied simultaneously on the real and imaginary components of the DRPE output plane. The compression and encryption technique consists in using an innovative randomized arithmetic coder (RAC) that can well compress the DRPE output planes and at the same time enhance the encryption. The RAC is obtained by an appropriate selection of some conditions in the binary arithmetic coding (BAC) process and by using a pseudo-random number to encrypt the corresponding outputs. The proposed technique has the capabilities to process video content and to be standard compliant with modern video coding standards such as H264 and HEVC. Simulations demonstrate that the proposed crypto-compression system has presented the drawbacks of the DRPE method. The cryptographic properties of DRPE have been enhanced while a compression rate of one-sixth can be achieved. FPGA implementation results show the high performance of the proposed method in terms of maximum operating frequency, hardware occupation, and dynamic power consumption.
    Full-text · Article · Feb 2016 · Optics Communications
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    • "Therefore, the resistance to brute-force attacks of this architecture is analogous to the one appearing in [24]. Otherwise, the security will be compromised, like in other conventional systems [11] [12] [13] [14] [15] [16] [17] [18], if an intruder has access to a subset of images belonging to the cyphertext and the optical parameters "
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    ABSTRACT: We propose a new nonlinear optical architecture based on a focus tunable lens and an iterative phase retrieval algorithm. It constitutes a compact encryption system that uses a single-random phase key to simultaneously encrypt (decrypt) amplitude and phase data. Summarily, the information encoded in a transmittance object (phase and amplitude) is randomly modulated by a diffuser when a laser beam illuminates it; once the beam reaches a focus tunable lens, different subjective speckle distributions are registered at some image plane as the focal length is tuned to different values. This set of speckle patterns constitutes a delocalized ciphertext, which is used in an iterative phase retrieval algorithm to reconstruct a complex ciphertext. The original data are decrypted propagating this ciphertext through a virtual optical system. In this system, amplitude data are straightforwardly decrypted while phase data can only be restored if the random modulation produced in the encryption process is compensated. Thus, an encryption-decryption process and authentication protocol can simultaneously be performed. We validate the feasibility of our proposal with simulated and experimental results.
    Full-text · Article · Feb 2016 · Journal of optics
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    • "From the cryptanalysis point of view, linearity leads to a low security level. Thus the DRPE method is vulnerable under various kinds of attack [32] [33] [34] and the adoption of image cryptosystem based on optical technology for real application should be cautious. "
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    ABSTRACT: The need for fast and strong image cryptosystems motivates researchers to develop new techniques to apply traditional cryptographic primitives in order to exploit the intrinsic features of digital images. One of the most popular and mature technique is the use of complex ynamic phenomena, including chaotic orbits and quantum walks, to generate the required key stream. In this paper, under the assumption of plaintext attacks we investigate the security of a classic diffusion mechanism (and of its variants) used as the core cryptographic rimitive in some image cryptosystems based on the aforementioned complex dynamic phenomena. We have theoretically found that regardless of the key schedule process, the data complexity for recovering each element of the equivalent secret key from these diffusion mechanisms is only O(1). The proposed analysis is validated by means of numerical examples. Some additional cryptographic applications of our work are also discussed.
    Full-text · Article · Dec 2015
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