A Dynamic Probabilistic and Space-Frequency Domain Composite Image Selective Encryption and Decryption Method

Abstract

The invention provides an image selective encryption and decryption method based on dynamic probability and space-frequency domain compositing. The MD5 value and SHA-1 value of a to-be-encrypted image are composited to improve the impact resistance of a single Hash feature, and intermediate key parameters are generated through close coupling to a user key to carry out probability interval division, probability generation and to-be-encrypted pixel screening and to determine a probabilistic encryption event and transform parameters. The designed encryption event includes a space domain and frequency domain replacement operation to improve the efficiency of encryption and avoid the influence of frequency domain coefficient overflow on the recovery of the visual quality of the image. According to the method, the encryption features of the to-be-encrypted image and the user key are updated, so that the key parameters under the condition of different number of encryption times differ greatly and are closely associated with the features of the to-be-encrypted image and the user key, and image visual quality and frequency domain overflow filtering control can be carried out through a preset encryption threshold. For decryption, an intermediate key set needs to be restored first, and then, the screened pixel blocks are decrypted reversely.

Description

technical field [0001] The invention belongs to the cross-research field of information security and digital image signal processing, relates to an image encryption and decryption method, in particular to an image selective encryption and decryption method based on dynamic probability and space-frequency domain compounding. Background technique [0002] Traditional image encryption is usually aimed at the entire image and is used to convert the entire image into an unrecognizable random dense image, which not only brings high computational costs, but also masks almost all features of the image to be encrypted except the size. In many practical applications, it is often not necessary to encrypt the entire image, but only to encrypt selected bit planes, regions, and some pixels of the image, and at the same time, it is necessary to provide some features of the original image to give potential More experience for users in exchange for greater commercial benefits, and the image ...

AI Technical Summary

Problems solved by technology

Wang Lihua, 2010 and Nidhi Taneja, 2011 both convert the image to the frequency domain and select specific frequency domain coefficients for encryption. In the frequency domain, selecting frequency domain coefficients with different importance can effectively control the visual quality of the image, but at the same time Encryption of frequency domain coefficients will also change the amplitude space of frequency domain coefficients, resulting in spatial domain pixel overflow and incorrect decryption

[0008] In addition to the above problems, selective image encryption also has security problems that exist in traditional image encryption, such as loose coupling of permutation and obfuscation processes, and the specific encryption strategy has nothing to do with the image to be encrypted.

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