Double-image encryption and decryption method

Abstract

The invention discloses a double-image encryption and decryption method which comprises: an image combination step of combing original images; a chaotic scrambling step of scrambling and expanding a combined image by using Logistic chaotic mapping; an image decomposition step of decomposing the chaotically-scrambled image; a modulation phase mask generating step of generating a phase mask based on a chaotic random sequence generated by the chaotic mapping and the decomposed image; a temporary image generating step of generating a temporary image according to the image obtained by decomposition and the phase mask; multi-parameter discrete fraction angle transformation steps of performing two-dimensional DMPFAT transformation on the temporary image and truncating a transformed phase part to obtain a final ciphertext image; an initial value of the chaotic mapping in chaotic scrambling and / or a parameter value of multi-parameter discrete fraction angle transformation are used as private secrete keys. The method disclosed by the invention is convenient for the storage, the transmission and the management of the secrete keys; the secret key space of a cryptographic system is enlarged, and the safety and the effectiveness of the method are improved.

Description

technical field [0001] The invention relates to the technical field of image encryption, in particular to a double image encryption and decryption method. Background technique [0002] In recent years, various optical encryption techniques have been introduced into image encryption, the most classic of which is the double random phase encoding technology proposed by Refregier and Javidi in the mid-1990s, which is often combined with various change domains to form optical encryption Systems such as Fractional Fourier Domain (FrRT), Fourier Domain (FT), Fresnel Domain (FrT), Discrete Cosine Transform Domain (DCT), Rotary Transform Domain (GT), Fractional Merlin Transform Domain and Fractional Angle Varying domains, etc., Alfalou and Brosseau point out that these techniques can be applied to compression operations simultaneously. Although these optical techniques are capable of processing multi-dimensional data at high speed, most methods focus on single images. Therefore, in...

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Problems solved by technology

[0003] Although the above two-image encryption methods can improve the efficiency of image transmission and communication, they all use the phase mask as the private key, which is not conducive to the storage, transmission and management of the key.

[0004] Lang Jun et al. proposed an image encryption method based on the multi-parameter discrete fractional Fourier transform (DMPFrFT), in which the security of the key depends on the additional parameters of the transformation without using the phase key, but the plaintext image is in the space domain and the transformation domain The non-linearity and disorder are weak, so the security of the encryption method is low, which is not conducive to the encrypted storage of double images

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