Key-space analysis of double random phase encryption technique

College of Engineering, Mathematics, and Physical Sciences, School of Electrical, Electronic, and Mechanical Engineering, University College Dublin, Ireland.
Applied Optics (Impact Factor: 1.78). 10/2007; 46(26):6641-7. DOI: 10.1364/AO.46.006641
Source: PubMed


We perform a numerical analysis on the double random phase encryption/decryption technique. The key-space of an encryption technique is the set of possible keys that can be used to encode data using that technique. In the case of a strong encryption scheme, many keys must be tried in any brute-force attack on that technique. Traditionally, designers of optical image encryption systems demonstrate only how a small number of arbitrary keys cannot decrypt a chosen encrypted image in their system. However, this type of demonstration does not discuss the properties of the key-space nor refute the feasibility of an efficient brute-force attack. To clarify these issues we present a key-space analysis of the technique. For a range of problem instances we plot the distribution of decryption errors in the key-space indicating the lack of feasibility of a simple brute-force attack.

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    • "Chosen-plaintext attack [19] and knownplaintext attack [20] have been introduced for testing the security of the random phase encoding [1], which is vulnerable because of the linearity of encryption process. Moreover, the key space of random phase encoding [1] has been analyzed numerically [21] [22]. Recently Alfalou and Brosseau have reported a complete discussion and comparison on optical encryption methods [23]. "
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    • "Furthermore, two dimensional optical encryption processing has been extended into a three dimensional spacebased encryption processing, where each pixel of the image is axially considered as one particle and phase-shifting digital holography technique is applied to the diffraction of all pixels in space (particles) [71] [72] [73] [74]. In the context of cryptography and cryptoanalysis, both chosen-plaintext [60] and known-plaintext attack [75] [76] [77] on DRPE have been examined, as have several other attacking methods [78] [79] [80] [81] [82] and the key space of DRPE technique itself [83] [84] [85] [86] has also been analysed. In this paper we review a number of optical image encryption methods proposed in the literature based on the architecture of the classic optical Double Random Phase Encoding (DRPE) system. "
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    • "Based on the DRPE method, some encryption algorithms have been considered and represented [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]. Furthermore the security of DRPE has been extensively analyzed at the aspects of key-space and attacks [17] [18] [19]. As a new tool, optical gyrator transform has been introduced into the research on the image encryption methods [20] [21] [22] [23] [24] [25]. "
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