• 디지털산업정보학회논문지
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• 제12권2호
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• pp.41-49
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• 2016

Lossless encryption methods are more applicable than lossy encryption methods when marginal distortion is not tolerable. In this research, the author propose a novel lossless symmetric key encryption/decryption technique. In the proposed algorithm, the image is transformed into the frequency domain using the lifting wavelet transform, then the image sub-bands are encrypted in a such way that guarantees a secure, reliable, and an unbreakable form. The encryption involves scattering the distinguishable frequency data in the image using a reversible weighting factor amongst the rest of the frequencies. The algorithm is designed to shuffle and reverse the sign of each frequency in the transformed image before the image frequencies are transformed back to the pixel domain. The results show a total deviation in pixel values between the original and encrypted image. The decryption algorithm reverses the encryption process and restores the image to its original form. The proposed algorithm is evaluated using standard security and statistical methods; results show that the proposed work is resistant to most known attacks and more secure than other algorithms in the cryptography domain.

• 정보처리학회논문지C
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• 제8C권5호
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• pp.525-534
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• 2001

일반적으로 무손실 영상압축 및 암호화 방법에는 압축과 암호화 과정이 독립적으로 이루어진다. 압축 후 암호화를 수행하면 압축열이 암호에 대한 평문으로 사용되므로 압축에 따른 엔트로피가 감소하여 랜덤한 성질을 갖게된다. 그러나 압축열 전체에 대한 암호화는 수행시간이 길어져 실시간 처리를 저해하는 원인이 되기도 한다. 본 논문에서는 무손실 영상압축과 암호의 결합에서 전체 처리시간을 줄이는 방법을 제안한다. 이는 쿼드트리 압축 알고리즘으로 그레이 영상을 분해하여 구조부분만을 암호화하는 방법이다. 아울러 영상의 무상관성과 동질영역을 확보하기 위한 변환과정을 수행하여 무손실 압축성능을 개선하였고, 쿼드트리 분해시 암호화되지 않은 데이터를 레벨별로 재구성하여 안전성을 갖도록 하였다. 모의 실험을 통하여 제안한 방법이 영상 압축율의 개선과 암호화 방법의 안전성 확보 및 실시간 처리가 가능함을 확인하였다.

• Current Optics and Photonics
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• 제4권4호
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• pp.302-309
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• 2020

An image encryption scheme based on the quick response (QR) code as a data container has aroused wide interest due to the lossless recovery of the decrypted image. In this paper, we apply this method to multi-image encryption. However, since the decrypted image is affected by crosstalk noise, the number of multi-image encryptions is severely limited. To solve this problem, we analyzed the performance of QR code as a data container, and processed the decrypted QR code using the proposed method, so that the number of multi-image encryptions is effectively increased. Finally, we implemented a large image (256 × 256) encryption and decryption.

• 디지털산업정보학회논문지
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• 제14권2호
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• pp.49-59
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• 2018

Encryption of digital images has been requested various fields. In the meantime, many algorithms based on a text - based encryption algorithm have been proposed. In this paper, we propose a method of encryption in wavelet transform domain to utilize the characteristics of digital image. In particular, wavelet transform is used to reduce the association between the encrypted image and the original image. Wavelet packet transformations can be decomposed into more subband images than wavelet transform, and various position permutation, numerical transformation, and visual transformation are performed on the coefficients of this subband image. As a result, this paper proposes a method that satisfies the characteristics of high encryption strength than the conventional wavelet transform and reversibility. This method also satisfies the lossless symmetric key encryption and decryption algorithm. The performance of the proposed method is confirmed by visual and quantitative. Experimental results show that the visually encrypted image is seen as a completely different signal from the original image. We also confirmed that the proposed method shows lower values of cross correlation than conventional wavelet transform. And PSNR has a sufficiently high value in terms of decoding performance of the proposed method. In this paper, we also proposed that the degree of correlation of the encrypted image can be controlled by adjusting the number of wavelet transform steps according to the characteristics of the image.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.264-267
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• 2005

COMS (Communication, Ocean, and Meteorological Satellite) will be launch at end of year 2008. For speedy and security communication of COMS, KARl (Korea Aerospace Research Institute) decided encryption and compression design. Encryption design is based on DES (Data Encryption Standard), so that encryption key generation and management are important issues in COMS operation. And Compression is based on loss and lossless JPEG (Joint Photographic Export Group) standard. JPEG is one of generally using compression algorithm in image.