Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard
Institute of Information Technology, Lodz University of Technology, 90-924 Lodz, Poland
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Academic Editor: Karsten Keller
Entropy 2021, 23(4), 421; https://doi.org/10.3390/e23040421
Received: 16 February 2021
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Revised: 19 March 2021
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Accepted: 29 March 2021
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Published: 31 March 2021
(This article belongs to the Special Issue Entropy Measures for Data Analysis II: Theory, Algorithms and Applications)
In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.
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Keywords:
encryption of images; compression of images; linear discrete parametric transforms; transform coding; uniform block quantization; entropy coding
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MDPI and ACS Style
Puchala, D.; Stokfiszewski, K.; Yatsymirskyy, M. Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard. Entropy 2021, 23, 421. https://doi.org/10.3390/e23040421
AMA Style
Puchala D, Stokfiszewski K, Yatsymirskyy M. Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard. Entropy. 2021; 23(4):421. https://doi.org/10.3390/e23040421
Chicago/Turabian StylePuchala, Dariusz, Kamil Stokfiszewski, and Mykhaylo Yatsymirskyy. 2021. "Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard" Entropy 23, no. 4: 421. https://doi.org/10.3390/e23040421
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