US 9,883,215 B2Granted

Method and device for compressing and expanding image intended for encrypted communication, program, and storage medium

AssigneeLightron International Co., Ltd.

InventorMitsuo Eguchi

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Abstract

An object of the present invention is to provide a method, a device, programs, and storage media for solving a problem that it is impossible to losslessly compress a digital image while being encrypted, to transmit the digital image, and to expand the digital image at a receiving side to restore the digital image with no artifact. An image or video is subjected to discrete convolution with an encryption key image, to be defocused beyond recognition, thus being encrypted, is further subjected to entropy-coding lossless compression, and is transmitted over the Internet. The compressed image or video is expanded at a receiving side, and iterative operations are performed on the basis of a Bayse probabilistic formula by using the separately-delivered encryption key image, to restore the image or video before encryption.

Claims20

Dependent claims

A cryptographic-communication image compressing/expanding method in which a digital image is compressed while being encrypted and is transmitted over a network, and the compressed digital image is expanded and decrypted at a receiving side, thereby restoring the digital image, the method being characterized by comprising:

(S1) an image retrieving step of retrieving a digital image;
(S2) a step of preparing a grayscale encryption key image with a desired encryption strength;
(S3) an encryption step of subjecting the digital image to convolution with the encryption key image, to remove high-frequency components in the digital image, to reduce the resolution thereof, and to encrypt the digital image, thus obtaining an encrypted image;
(S4) a step of subjecting the encrypted image to entropy coding, thus converting the encrypted image into encrypted-image code;
(S5) a step of transmitting the encrypted-image code to another computer on the network;
(S6) a step of receiving the encrypted-image code at said another computer;
(S7) a step of decoding, at said another computer, the encrypted-image code by using a decoding method corresponding to encoding used for the entropy coding, thus generating a received encrypted image;
(S8) a step of decrypting and preparing, at said another computer, the encryption key image, which is encrypted in advance, is separately delivered, and is used in the encryption step;
and
(S9) a digital-image restoring step of restoring, at said another computer, from the encryption key image and the received encrypted image, a maximum-likelihood digital image that has the maximum likelihood of the received encrypted image, wherein the encryption key image is an image of which a color of a background is black and having a design at its center.

7 more elements

A cryptographic-communication image compressing/expanding system in which a digital image is compressed while being encrypted and is transmitted over a network, and the compressed digital image is expanded and decrypted to restore the digital image at a receiving side, comprising:

a memory in communication with a processor to:
(W1) retrieve a digital image;
(W2) prepare a grayscale encryption key image with a desired encryption strength;
(W3) subject the digital image to convolution with the encryption key image, to remove high-frequency components in the digital image, to reduce the resolution thereof, and to encrypt the digital image, thus obtaining an encrypted image;
(W4) subject the encrypted image to entropy coding, thus converting the encrypted image into encrypted-image code;
(W5) transmit the encrypted-image code to another computer on a network;
(W6) receive, at said another computer, the encrypted-image code;
(W7) decode, at said another computer, the encrypted-image code by a decoding method corresponding to encoding used to perform entropy coding, thus generating a received encrypted image;
(W8) decrypt and prepare, at said another computer, the encryption key image, which is encrypted in advance, is separately delivered, and is used in the encryption means;
and
(W9) restore, at said another computer, from the encryption key image and the received encrypted image, a maximum-likelihood digital image that has the maximum likelihood of the received encrypted image, wherein the encryption key image is an image of which a color of a background is black and having a design at its center.

8 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/104,616Filed 27 Nov 2014
Priority: JP 2013-25904616 Dec 2013
Published: US 2016/0330492 A110 Nov 2016
Granted: 30 Jan 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification9 codes

H04N 21/2347
Processing of video elementary streams, e.g. splicing of video streams or manipulating encoded video stream scene graphs: involving video stream…
G09C 5/00
Ciphering apparatus or methods not provided for in the preceding groups
H04N 19/426
Characterised by memory arrangements: using memory downsizing methods
H04N 19/59
Using predictive coding: involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution

Family

US 2016/0330492 A1Pre-grant publication · published 10 Nov 2016
US 9,883,215 B2This patent

From the US filing history. Foreign family members aren’t listed.

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