CN104077739A - Color image quick encryption method - Google Patents
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- CN104077739A CN104077739A CN201410313967.5A CN201410313967A CN104077739A CN 104077739 A CN104077739 A CN 104077739A CN 201410313967 A CN201410313967 A CN 201410313967A CN 104077739 A CN104077739 A CN 104077739A
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Abstract
The invention discloses a color image quick encryption method implemented on the basis of Arnold transform. The method includes the steps that an image is chunked according to the size of the image before encryption, then positions and gray levels of three primary color components of an image pixel are scrambled at the same time by means of Arnold transform to achieve encryption of the color image, and inverse transformation is carried out on transform in the preceding steps to decrypt the encrypted image. Through improvement of the prior art, the encryption effect is improved, encryption efficiency is improved, and the application range is widened.
Description
Technical field
The present invention relates to a kind of digital signal encryption method, be specifically related to a kind of coloured image fast encrypt method.
Background technology
Coloured image, as a chief component of multi-medium data, in order to ensure its security in transmitting procedure, carry out reliable encryption.Current many cryptographic algorithm only limit to bianry image or gray level image.Color image data is compared with general text data, the degree of correlation of data message amount greatly and between data is high, ciphering process should consider that the change of subjective visual effect considers the change of correlativity between objective data again, and the operand of encryption is large, consuming time many; The color image encryption of transmission is required to have real-time, therefore the research of encryption efficiency is seemed to particularly important.
In recent years, a lot of articles have proposed the image encryption algorithm based on chaos system or hyperchaotic system, but they more the security of encrypting as: the aspects such as key space, pixel interdependence are improved and are analyzed, and have conventionally all ignored the efficiency of encryption system.In fact, because the generation of chaos sequence itself just needs considerable time, even if encrypt in only need scramble one time, total time also long.
Arnold conversion is simple owing to encrypting, without producing ciphering sequence, thus be a kind of conventional digital image inverse transformation encryption, but there is following shortcoming in it:
(1) conversion of the Arnold scramble of low-dimensional can not change the gray distribution features of pixel, and security is lower, and cipher round results is undesirable, and the Time Dependent encryption period of encrypting and deciphering, and speed is subject to the restriction in cycle;
(2) the intensity profile characteristic that can change pixel when the Arnold of higher-dimension converts, security is good, but the iteration cycle of the Arnold scramble of higher-dimension conversion is longer, and deciphering efficiency is low;
(3) shape of Arnold transfer pair image has requirement, and Arnold transform operation is only applicable to square formation, and this has also restricted the usable range of encryption system greatly.
Summary of the invention
Goal of the invention of the present invention is to provide a kind of coloured image fast encrypt method, by cipher round results that prior art has been improved, has improved encryption efficiency, has expanded the scope of application.
To achieve the above object of the invention, the technical solution used in the present invention is: a kind of coloured image fast encrypt method, based on Arnold, conversion realizes, and it is characterized in that, comprises the steps:
1) according to picture size, image is carried out to piecemeal processing;
2) utilize Arnold conversion simultaneously the position to three of image pixel primary color components and gray scale carry out scramble, complete the encryption of coloured image;
3) to step 2) in conversion carry out inverse transformation, complete the deciphering to encrypted image.
In technique scheme, in described step 1), establish length and the wide wm of being respectively and the wn of image,
, image is divided into N piece, the size of every block of image is
, wherein,
,
expression is got
smallest positive integral, when encryption according to block encryption of order, if the curtailment wn of last piece supplies length wn with encrypted adjacent image.
In technique scheme, described step 2) in, the sampled data of establishing coloured image is a three-dimensional matrix
w ,
w(
x,
y, 1),
w(
x,
y, 2) and
w(
x,
y, 3) denotation coordination be (
x,y) locate the gray-scale value of three primary color components of pixel,
w '(
x,
y, 1),
w '(
x,
y, 2) and
w '(
x,
y, 3) represent the gray-scale value after changing, coordinate be (
x,y) locate pixel three primary color components value change after move to coordinate (
x ', y ') locate, as the formula (1):
（1）
In formula (1), position (
x,y) with (
x ',
y ') between relation change according to formula (2); Gray-scale value
wwith
w 'between relation change according to formula (3):
（2）
（3）。
In technique scheme, in described step 3), when deciphering, coordinate be (
x ', y ') locate pixel three primary color components value change after move to coordinate place (
x,y) locate, as the formula (4), decrypting process is an inverse process of encrypting, and does not rely on transformation period,
（4）
In formula (4), (
x ',
y ') with (
x,y) between position relationship carry out inverse conversion according to formula (5); Gray-scale value
w 'with
wbetween relation carry out inverse conversion according to formula (6):
（5）
（6）。
Because technique scheme is used, the present invention compared with prior art has following advantages:
1. the present invention adopts the method for block encryption, makes the shape of image no longer be confined to square, thereby has expanded the scope of application.
2. the present invention changes position and the gray-scale value of image pixel simultaneously, has improved the security of encrypting, and has improved cipher round results.
3. the present invention adopts improved inverse transformation to make decrypting process not rely on transformation period, thereby has improved deciphering efficiency.
Brief description of the drawings
Fig. 1 is process flow diagram of the present invention in embodiment mono-.
Fig. 2 is the design sketch that in embodiment bis-, a square-shaped image is encrypted and is deciphered.
Fig. 3 is cipher round results comparison diagram in embodiment bis-.
Fig. 4 is the intensity profile characteristic schematic diagram of image before and after encrypting in embodiment bis-.
Fig. 5 is the encryption and decryption schematic diagram to rectangle diagram picture in embodiment bis-.
Embodiment
Below in conjunction with drawings and Examples, the invention will be further described:
Embodiment mono-: shown in Figure 1, a kind of coloured image fast encrypt method, based on Arnold, conversion realizes, and comprises the steps:
1) according to picture size, image being carried out to piecemeal processes;
2) utilize Arnold conversion simultaneously the position to three of image pixel primary color components and gray scale carry out scramble, complete the encryption of coloured image;
3) conversion in step (2) is carried out to inverse transformation, complete the deciphering to encrypted image.
In the present embodiment, in described step 1), establish length and the wide wm of being respectively and the wn of image,
, image is divided into N piece, the size of every block of image is
, wherein,
,
expression is got
smallest positive integral, when encryption according to block encryption of order, if the curtailment wn of last piece supplies length wn with encrypted adjacent image.
In described step (2), the sampled data of establishing coloured image is a three-dimensional matrix
w ,
w(
x,
y, 1),
w(
x,
y, 2) and
w(
x,
y, 3) denotation coordination be (
x,y) locate the gray-scale value of three primary color components of pixel.
w '(
x,
y, 1),
w '(
x,
y, 2) and
w '(
x,
y, 3) represent change after gray-scale value.Coordinate be (
x,y) locate pixel three primary color components value change after move to coordinate (
x ', y ') locate.As the formula (1):
（1）
In formula (1), position (
x,y) with (
x ',
y ') between relation change according to formula (2); Gray-scale value
wwith
w 'between relation change according to formula (3):
（2）
（3）。
In described step (3), when deciphering, coordinate be (
x ', y ') locate pixel three primary color components value change after move to coordinate place (
x,y) locate, as the formula (4), decrypting process is an inverse process of encrypting, and does not rely on transformation period,
（4）
In formula (4), (
x ',
y ') with (
x,y) between position relationship carry out inverse conversion according to formula (5); Gray-scale value
w 'with
wbetween relation carry out inverse conversion according to formula (6):
（5）
（6）。
Embodiment bis-: shown in Figure 2, the coloured image of one 256 × 256 is encrypted and decryption processing to wherein (a) and (b) be respectively the image after encryption and decryption, the encryption and decryption 0.703000s that takes time altogether, compared with prior art, most effectively improve more than 80 times.
Shown in Figure 3, adopt diverse ways to be encrypted to same width coloured image, wherein, (a) be original image; (b) be the image of encrypting based on after Arnold transformation conversion, this conversion can only change the position of pixel, can not change the gray-scale value of pixel; (c) be the image of encrypting based on after three-dimensional Arnold conversion, this conversion has only changed the gray-scale value of pixel, and the profile of original image is left in subregion; (d) image of encrypting for technical solution of the present invention, COLOR COMPOSITION THROUGH DISTRIBUTION is even, intuitively respond well.
Shown in Figure 4, the intensity profile characteristic of the red component of expression coloured image, in figure, transverse axis is gray level, and transformation range is 0～255, and the longitudinal axis is number of pixels corresponding to each gray level.Wherein, (a) be the intensity profile of original image; (b) be the intensity profile of image after Arnold transformation transposition encryption; (c) be the intensity profile of image after three-dimensional Arnold transposition encryption; (d) be the intensity profile of technical solution of the present invention encrypted image.Can find out, (b) intensity profile of figure is the same with original image, so image does not change intensity profile characteristic after Arnold transformation transposition encryption.
Shown in Figure 5, the rectangle colorful image of 414 × 187 is encrypted and decryption processing, wherein, (a) be original image; (b) be the image after encrypting; (c) be the image after deciphering, encryption and decryption are 0.766000s consuming time altogether, and the image that visible technical solution of the present invention is encrypted is not subject to the restriction of shape.
Claims (4)
1. a coloured image fast encrypt method, based on Arnold, conversion realizes, and it is characterized in that, comprises the steps:
1) according to picture size, image is carried out to piecemeal processing;
2) utilize Arnold conversion simultaneously the position to three of image pixel primary color components and gray scale carry out scramble, complete the encryption of coloured image;
3) to step 2) in conversion carry out inverse transformation, complete the deciphering to encrypted image.
2. a kind of coloured image fast encrypt method according to claim 1, is characterized in that: in described step 1), establish length and the wide wm of being respectively and the wn of image,
, image is divided into N piece, the size of every block of image is
, wherein,
,
expression is got
smallest positive integral.
3. a kind of coloured image fast encrypt method according to claim 1, is characterized in that: described step 2) in, the sampled data of establishing coloured image is a three-dimensional matrix
w ,
w(
x,
y, 1),
w(
x,
y, 2) and
w(
x,
y, 3) denotation coordination be (
x,y) locate the gray-scale value of three primary color components of pixel,
w '(
x,
y, 1),
w '(
x,
y, 2) and
w '(
x,
y, 3) represent the gray-scale value after changing, coordinate be (
x,y) locate pixel three primary color components value change after move to coordinate (
x ', y ') locate, as the formula (1):
（1）
In formula (1), position (
x,y) with (
x ',
y ') between relation change according to formula (2); Gray-scale value
wwith
w 'between relation change according to formula (3):
（2）
（3）。
4. a kind of coloured image fast encrypt method according to claim 1, is characterized in that:, in described step 3), when deciphering, coordinate be (
x ', y ') locate pixel three primary color components value change after move to coordinate place (
x,y) locate, as the formula (4),
（4）
In formula (4), (
x ',
y ') with (
x,y) between position relationship carry out inverse conversion according to formula (5); Gray-scale value
w 'with
wbetween relation carry out inverse conversion according to formula (6):
（5）
（6）。
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| CN201410313967.5A CN104077739A (en) | 2014-07-03 | 2014-07-03 | Color image quick encryption method |
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| CN201410313967.5A CN104077739A (en) | 2014-07-03 | 2014-07-03 | Color image quick encryption method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108882029A (en) * | 2018-06-29 | 2018-11-23 | 银河威尔科技（北京）有限公司 | A kind of decryption of video method and apparatus |
| CN110414448A (en) * | 2019-07-31 | 2019-11-05 | 北京三快在线科技有限公司 | Image processing method, device, electronic equipment and storage medium |
| CN111030810A (en) * | 2019-11-29 | 2020-04-17 | 童勤业 | Anti-counterfeiting encryption method based on image local random transformation technology |
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2014
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| CN101894359A (en) * | 2010-07-13 | 2010-11-24 | 北京信息科技大学 | Image scrambling encryption method |
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| CN103761703A (en) * | 2014-01-15 | 2014-04-30 | 西安理工大学 | Single channel color image encryption method based on GT conversion and chaos |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108882029A (en) * | 2018-06-29 | 2018-11-23 | 银河威尔科技（北京）有限公司 | A kind of decryption of video method and apparatus |
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| CN110414448A (en) * | 2019-07-31 | 2019-11-05 | 北京三快在线科技有限公司 | Image processing method, device, electronic equipment and storage medium |
| CN111030810A (en) * | 2019-11-29 | 2020-04-17 | 童勤业 | Anti-counterfeiting encryption method based on image local random transformation technology |
| CN111030810B (en) * | 2019-11-29 | 2022-08-05 | 童勤业 | Anti-counterfeiting encryption method based on image local random transformation technology |
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Application publication date: 20141001 |