WO2002039411A1

WO2002039411A1 - Apparatus and method for encrypting/decrypting information on a pixel-by-pixel basis and encryption/decryption system using the same

Info

Publication number: WO2002039411A1
Application number: PCT/KR2001/001918
Authority: WO
Inventors: Young-Sun Cho; Young-Sik Nam; Woo-Jin Lee; Seok-Jin Park; Hee-Seok Kang
Original assignee: Alphalogix Co., Ltd.
Priority date: 2000-11-10
Filing date: 2001-11-10
Publication date: 2002-05-16
Also published as: AU2002224158A1

Abstract

An apparatus and method for encrypting/decrypting information, and the encrypting/decrypting system using the same, and a computer readable recording medium storing programs for realizing the above are disclosed. The method for encrypting/decrypting an image includes the steps of: a) receiving an information to be encrypted; b) generating a random number map for a encryption; c) decomposing the information to be encrypted into a plurality of pixels; d) performing multi step encryption by changing a position and a color of the pixel using the random number map for the encryption, and generating encrypted information; e) outputting the encrypted information; f) receiving the encrypted information; g) gaining a security code for decoding the encrypted information; h) generating a random number map for a decryption; i) performing a multi step decryption by inverse-changing a position and a color of the pixel of the encrypted information using the random number map for the decryption; j) restoring an original image by combining the decrypted pixels and generating a restored information; and k) outputting the restored information.

Description

APPARATUS AND METHOD FOR ENCRYPTING/DECRYPTING INFORMATION

ON A PIXEL-BY-PIXEL BASIS AND ENCRYPTION/DECRYPTION SYSTEM USING THE SAME

Description

Technical Field

The present invention relates to an apparatus and method for encrypting/decrypting information, and the encrypting/ decrypting system using the same, and a computer readable recording medium storing programs for realizing the above; and, more particularly, to^' an apparatus and method for encrypting/decrypting information in which an image is encrypted by re-arranging pixels of the image and changing colors of the image on a pixel by pixel basis under the use of a personal security code, an encryption key code managed by an authorized organization, a high security encryption algorithm and a random numbers algorithm, so that a decryption of the image is impossible without an exclusive decrypting device, an encrypting/decrypting system using the same, and a computer readable recording medium storing programs for the realization of the above.

Background Art of the Invention

In this specification, an encryption/decryption on a pixel by pixel basis means the encryption/decryption of each pixel and the encryption/decryption of each pixel group, the pixel group including a predetermined number of pixels.

In general, forged passports are being used for international terrorism, drug contraband, smuggling into a country, etc., and forged identification cards are being used for different kinds of crimes such as employment of a minor at a red-light district, real estate swindling, identity fraud of a criminal, etc., causing serious damage socially and nationally. Also, since a seal impression of a bankbook, or a signature of a credit card, etc. are printed and exposed intact as the original, it is not difficult to forge them when robbed or lost even though the forger is not an expert, causing different kinds of financial accidents such as unlawful withdrawal of a deposit, etc. Furthermore, forgery of holograms of credit cards, department store gift certificates, trademarks, etc. happens frequently.

Conventionally, special printing technologies such as non-fluorescence, optical interference pattern, micro- lettering, intaglio, security thread and watermark are applied in a combination, but forgery still remains as serious as to be called a history of a war against forgers. For these reasons many countries are investing their human and material resources for the prevention of forgery. Up to now, accurate printing technologies, with the use of special materials, such as bar code, hologram, watermark and micro lettering have been used as a forgery preventing method for printings. However, these special printings may make the forgery difficult, but they cannot fundamentally prevent the forgery, due to the remarkable development of a color copy machine and a computer technology together with the development of the forgery techniques by expert forgery organizations.

The development of such forgery techniques is one problem, but another reason for the ceaseless forgery is that the general public is not able to determine easily whether something is forged or not. Considering that forgery is caused by the lack of knowledge or carefulness of the general public in determining whether something is forged or not easily, such forgery can be settled if a method of simply informing the forgery.

A basic concept and method of an image information security system is disclosed in a patent application (Korea Patent Application No. 1999-2625) filed by the same applicant of the present invention on January 27, 1999. In the application, an image data is read by an image sensor and then the image is separated into minute pieces based on regular triangle shape, re-arranging positions of the pieces according to a given security code, encrypting by only increasing the number of the re-arrangements. Even though the above method takes a long time in decoding with the current computer system, the time will be rapidly shortened, considering the present development trend of the computer technology. The image information security system of the patent application is highly secure at the present, however, in order to strengthen the security more, the image data has to be decomposed into a plurality of pixels, and also the inversion of color of pixels is needed so as not to be inverse-estimated.

Accordingly, this applicant has invented a new encryption method to which a high security algorithm and a multi step encryption procedure were applied on a pixel-by- pixel basis differentiating from the conventional methods. By employing such new encryption method, encryption (issuance) apparatus for preventing forgery, and a practical decryption (decoding) apparatus, which could be easily used not only by experts but also by general public, were invented.

Summary of the Invention

Therefore, it is an object of the present invention to provide an encryption apparatus , a method thereof and a computer readable recording medium storing programs to realize the inventive method, in which an input image is encrypted by being decomposed into a plurality of pixels and puzzled, and then positions of the pixels being changed irregularly. Another object of the present invention is to provide an encryption apparatus, a method thereof and a computer readable recording medium storing programs to realize the inventive method, in which an input image is encrypted by being decomposed into a plurality of pixels and puzzled, and then positions as well as colors of the pixels are changed irregularly.

A further another object ,of the present invention is to provide an encryption apparatus, a method thereof and a computer readable recording medium storing programs to realize the inventive method, in which input information is encrypted based on a personal peculiar security code, an encryption key code managed by an organization, a high security encryption algorithm with guaranteed stability and a random number algorithm. A still further object of the present invention is to provide an image information encryption apparatus , a method thereof and a computer readable recording medium storing programs to realize the inventive method, in which forgery executed by a third party besides the corresponding authority is impossible.

An additional object of the present invention is to provide a decryption apparatus which decrypts the encrypted information on a pixel by pixel basis in real time and informs whether there is forgery in the decrypted information or not, a method thereof and a computer readable record of the programs to realize the inventive method.

A still further object of the present invention is to provide an encryption/decryption system and method thereof, which are gotten by mutually interlocking the above encryption apparatus and method and the above decryption apparatus and method, and to provide a computer readable record of the programs to realize the inventive method.

In accordance with an aspect of the present invention, there is provided a method for encrypting an image on a pixel-by-pixel basis, comprising the steps of: a) receiving information to be encrypted; b) generating a random number map; c) decomposing the information into a plurality of pixels; d) encrypting the pixels and generating encrypted information; and e) outputting the encrypted information.

In accordance with another aspect of the present invention, there is provided a method for decrypting an image on a pixel-by-pixel basis, comprising the steps of: a) receiving an encrypted information; b) gaining a security code used for decoding the encrypted information; c) generating a random number map; d) decrypting the encrypted information on a pixel by pixel basis and generating decrypted pixels; e) combining the decrypted pixels and generating a restored information; and f) outputting the restored information.

In accordance with another aspect of the present invention, there is provided an apparatus for encrypting an image on a pixel by pixel basis, comprising: an input unit for receiving information to be encrypted; a security code input unit for receiving a security code; an encryption unit for decomposing the information into a plurality of pixels and for encrypting the pixels, thereby generating an encrypted information; a storing unit for storing the encrypted information; and an output unit for outputting the encrypted information.

In accordance with further another aspect of the present invention, there is provided an apparatus for decrypting an image on a pixel by pixel basis, comprising: an input unit for receiving an encrypted information; a security code obtaining unit for gaining a security code; a decryption unit for decrypting the encrypted information on a pixel by pixel basis, combining the decrypted pixels, and generating restored information; a storing unit for storing the restored information; and an output unit for outputting the restored information.

In accordance with still further another aspect of the present invention, there is provided^' method for encrypting/decrypting an image on a pixel-by-pixel basis, comprising the steps of: a) receiving an information to be encrypted; b) generating a random number map for a encryption; c) decomposing the information to be encrypted into a plurality of pixels; d) performing multi step encryption by changing a position and a color of the pixel using the random number map for the encryption, and generating encrypted information; e) outputting the encrypted information; f) receiving the encrypted information; g) gaining a security code for decoding the encrypted information; h) generating a random number map for a decryption; i) performing a multi step decryption by inverse-changing a position and a color of the pixel of the encrypted information using the random number map for the decryption; j) restoring an original image by combining the decrypted pixels and generating a restored information; and k) outputting the restored information. In accordance with still further another aspect of the present invention, there is provided an apparatus for encrypting/decrypting an image on a pixel-by-pixel basis, said apparatus comprising: an input unit for receiving encrypted information and information to be encrypted; a security code input unit for receiving a security code for an encryption; a multi step encryption unit for multi step encryption by decomposing the information into a plurality of pixels, and changing a position and a color of the pixel using a random number map for an encryption; a security code obtaining unit for gaining a security code for a decryption; a multi step decryption unit for multi step decryption by inverse-changing the position and the color of the pixel of the encrypted image using the random number map, and then, restoring an original image by combining the decrypted pixels and generating restored information; a storing unit for storing the encrypted information and the restored information; and an output unit for outputting the encrypted image and the restored information.

In accordance with still further another aspect of the present invention, there is provided a computer readable recording medium storing instructions for executing a method for encrypting an image on a pixel by pixel basis in an encryption apparatus equipped with a processor, the method comprising the steps of: a) receiving information to be encrypted; b) generating a random number map; c) decomposing the information into a plurality of pixels; d) encrypting the pixels and generating encrypted information; and e) outputting the encrypted information.

In accordance with still further another aspect of the present invention, there is provided a computer readable recording medium storing instructions for executing a method for decrypting an image on a pixel-by-pixel basis in a decryption apparatus equipped with a processor, the method comprising the steps of: a) receiving an encrypted information; b) gaining a security code used for decoding the encrypted information; c) generating a random number map; d) decrypting the encrypted information on a pixel by pixel basis and generating decrypted pixels; e) combining the decrypted pixels and generating a restored information; and f) outputting the restored information.

In accordance with yet another aspect of the present invention, there is provided a computer readable recording medium storing instructions for executing a method for encrypting/decrypting an image on a pixel-by-pixel basis, in an encryption/ decryption apparatus equipped with a processor, the method comprising the steps of: a) receiving an information to be encrypted; b) generating a random number map for a encryption; c) decomposing the information to be encrypted into a plurality of pixels; d) performing multi step encryption by changing a position and a color of the pixel using the random number map for the encryption, and generating encrypted information; e) outputting the encrypted information; f) receiving the encrypted information; g) gaining a security code for decoding the encrypted information; h) generating a random number map for a decryption; i) performing a multi step decryption by inverse-changing a position and a color of the pixel of the encrypted information using the random number map for the decryption; j) restoring an original image by combining the decrypted pixels and generating a restored information; and k) outputting the restored information.

Like this, the apparatus for the encryption/decryption method of this invention is embodied by an issuance apparatus (encryption apparatus) to which a forge preventing technique is applied, and by a decoding apparatus (decryption apparatus), which is capable of determining whether there is forgery of not.

In the above issuance apparatus, an encryption method and a hacking preventing technology capable of protecting, in the most efficient way, image information of a limited space area such as photo, signature, seal impression, peculiar pattern, etc., are applied.

The encryption method prevents a possibility of the forge doubly, trebly by employing a personal peculiar security code and an encryption key code managed by an authority, a high security encryption algorithm with guaranteed stability, and a random number algorithm. Especially, it is included a procedure of decomposing the image data into a plurality of pixels puzzling and re- arranging irregularly, and changing the color according to the random number algorithm in order to prevent decryption through an inference technique.

Here, one-step encryption is possible even with the procedure of making the image data puzzled on a pixel-by- pixel basis. That is, the color converting procedure is an additional element. In this specification, a multi step encryption and decryption will be described, however, it is apparent to one skilled in the art that one-step encryptioncan be applied to all following embodiments. As stated above, in the present invention, the image is changed on a pixel by pixel basis according to the random number algorithm and an encryption algorithm, to thereby make the decoding impossible without an exclusive decoding apparatus, and make the forgery of identification card, card, paper money and bankbook, impossible. Further, in case that there is a miscellaneous image, the image is restored using the multi step image processing technique, to thus obtain a stable restoration.

Brief Description of the Drawings

The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments along with the attached drawings, in which:

Fig. 1A shows that image data is decomposed into a plurality of pixels so as to heighten security and stability in an encryption or decryption procedure in accordance with the present invention; Fig. IB shows image data whose positions are changed each pixel by pixel in accordance with the present invention;

Fig. IC shows image data whose color is converted each pixel by pixel in accordance to the present invention; Fig. 2 is a block diagram for one embodiment of an encryption apparatus on a pixel-by-pixel basis in accordance with the present invention^';

Fig. 3 is a block diagram for one embodiment of a decryption apparatus on a pixel-by-pixel basis in accordance with the present invention;

Fig. 4 indicates an overall flowchart for one embodiment of an encryption method on a pixel-by-pixel basis in accordance with the present invention;

Figs. 5A and 5B provide flowcharts for one embodiment of a multi step encryption procedure on a pixel by pixel basis in accordance with Fig. 4;

Fig. 6 depicts an overall flowchart for one embodiment of a decryption method on a pixel by pixel basis in accordance with the present invention; and Figs. 7A and 7B set forth flowcharts for one embodiment of a multi step decryption procedure on a pixel- by-pixel basis in accordance with Fig. 6.

Best Mode for Carrying Out the Invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings .

With reference to Figs. 1A through IC, a technical gist of the present invention can be described as follows.

In accordance with the present invention, an encryption method ' largely includes a pre-processing procedure, a multi step encryption procedure and a postprocessing procedure. The pre-processing procedure includes an input procedure and a normalization procedure.

This input procedure is' the procedure of inputting analog type information such as actual image or text, through an image input unit (e.g., image sensor, etc.), and converting it into digital information, or the procedure of transferring existing information already digitized from a database to an encryption apparatus. Here, the image input unit can be an image sensor, such as camera or scanner, etc., and database means a large of the image information stored in a predetermined form, which has already been received through the image input unit. The inputted image goes through a multi step encryption procedure after a normalization procedure.

In the normalization procedure, color control, visibility, threshold and size control take place. The inputted image through the image input unit, except of the digital image stored at the database, is changed from analog data to digital data, thus, its color is controlled to maintain the color of the original image as much as possible. In order to provide an exact threshold after the color control, a visibility procedure is performed by omitting a high frequency area from an original frequency area, and then, by extending the remained frequency area by times of a peculiar constant number. After the visibility procedure, a threshold by the p number (p < N) is performed, to convert color, using N number colors. In this invention, p=2 is used as an example. After the threshold procedure, the size is controlled considering the correlation with the neighboring pixel to gain the most approximate image to the original image, lessening as much as possible the data loss of the inputted image.

The second multi step encryption procedure contains a decomposing procedure of the image into a plurality of pixels, a puzzling and a color converting procedure of the pixels to be described. in detail later.

The third post-processing procedure contains a procedure of inserting an encryption key code into the encrypted image, a procedure of inserting an border line into the encrypted image (not shown in the drawing), and an encrypted image outputting procedure. In the encryption key code inserting procedure, the encryption key code is inserted into an optional portion of the encrypted image. This procedure may be omitted in the case of receiving directly the security key and using in the decryption procedure. Further, in the borderline inserting procedure, the borderline for distinguishing an encrypted image portion from the background is inserted into an outer side of the encrypted image in order to exactly extract the image in the decryption procedure. This procedure can be performed at any time during the multi step encryption procedure, and before the outputting procedure, which is not an essential component. In the encrypted image outputting procedure, the encrypted image is outputted as digital information or is printed on a printing sheet according to its application. This printing procedure has an output based on material capable of outputting the encrypted image and based on an optionally decided position by predetermined N number colors. At this time, since the outputted image from the printer is a combination of pieces entirely different from the original image, it is impossible to know the original image. For example, in the case of encrypting a photo image of a passport or an identification card, or personal information etc., (encrypting with one color (N=l), for example yellow), it is printed in yellow without any shape. Therefore, if the background of the passport is yellow, it can obtain even the effect of concealment. Also, in case of printing text information on the encrypted image, the text information may act as noise but it would have almost no influence in restoring the original image.

The detailed technical gist on the encryption method of the present invention is described as follows.

The encryption method of this invention includes procedures of generating a random number map, decomposing information into a plurality of pixels, puzzling the pixel using the random number map, and converting the color of the pixel using the random number map.

Herewith, the procedure of converting the color of the pixel using the random number map is not an essential component of the invention, but an additional one. Also, the color converting procedure converts the color by utilizing pre-determined N number colors (inversion of colors). At this time, among the N (N = p + k) number colors, p number colors are utilized in the original image information processing, and k number colors are utilized in error correction. Also, in the pixel color converting procedure, the color of the respective pixels can be converted variously from one color (N=l) to N colors. Hereby, in case that the image data to be encrypted is a text image, k can have an optional value, and in case of a video image, k can have a value of 0.

Further, the procedure of decomposing the information (image data) into a plurality of pixels is a procedure to heighten the security of the encrypted image, and it is the procedure of decomposing the inputted image data by the image input unit, into a plurality of pixel. Fig. 1A represents an optional image information composed of pure colors like R(Red), G(Green), B(Blue), and W(White) divided into a plurality of pixels in accordance with the present invention.

In the procedure of generating the random number map, it can be used a random number generator only, or a random number generator with a random number map generator. Now, the random number generator can utilize various algorithms such as DES and SEED etc. The random number map is provided to process the multi step encryption (equally applied in the decryption procedure to be described later), and three random number maps are generated. Here, all of three encryption keys used are different from one another. Among three random number maps, the first random number map and the second random number map are used for the puzzling procedure as shown in Fig. IB, and the third random number map is used for the color converting procedure (color inversion procedure) as shown in Fig. IC. The two random number maps used for the puzzling procedure, the first one is used for a substitution on matrix unit basis, and the second one is used for a substitution on a pixel-by-pixel basis. Here, the substitution on matrix unit basis means that positions are changed row with another row, and column with another column, and the substitution based on a pixel-by-pixel basis means that positions are changed pixel by pixel.

The range 'm₀' of the generated first random number map component is represented as 0 < m₀ ≤ (R^χ C), wherein R indicates a row of the map, and C indicates a column, and m₀ can have a fixed number larger than 0 up to R x C as the greatest value provided when elements of the map are represented in an enumeration type. The range 'mi' of the generated second random number map component is equal to mo- There are two reasons why the random number map is applied by two steps like the above. The first reason is that the encryption key codes used to generate respective random number maps are different, getting this way a higher security and higher stability, and the second reason is the ability to generate the needed random number map of a uniform distribution.

According to two random number maps above-mentioned, the positions of pixel 1 and pixel 2 of Fig. 1A are changed to pixel 1 and pixel 2 of Fig. IB respectively.

The third random number map is used for the conversion of color (color inversion) based on a pixel-by-pixel basis, which is the minimum puzzle unit. The number of colors used for converting the color in the minimum puzzle unit is the N (1 ≤ N ≤ the number of distinguishable colors) number, and here the range m of the generated random number map component is equal to N.

The color converting procedure by such third random number map is as shown in Fig. IC. The color of pixel 1 and pixel 2 of Fig. IB are converted individually and differently to pixel 1 and pixel 2 of Fig. IC.

Meantime, text information can be processed regarding the letter shape itself as an image, or using a code representing the letter shape. The former can be processed by the above-described method, and the latter can be processed by optionally defining a color corresponding to bits which constitute the code, for instances, 0 is white and 1 is black, etc. On the other hand, if the encrypted image is generated in a specific color (e.g., yellow), and printed on a specific portion of a printing sheet of the same color (e.g., yellow printing sheet) at its application procedure as afore-mentioned, illegal forgers would not be able to know even where the encryption is. Also, in case of using several colors (e.g., red, orange, yellow, green, blue, dark blue, purple etc.), the same effect can be obtained by utilizing various colors as the background color of the printing sheet. Though an application method in printing the encrypted image was described in the above example, it can also be applied differently like storing the encrypted image as digital information, or transmitting the encrypted image to a decoding apparatus through a transmitting apparatus. Meanwhile, the decryption method is processed in inverse-order of the above encryption method.

In accordance with the present invention, the decryption method includes an encrypted image preprocessing procedure, a multi step decryption procedure, and a post-processing procedure. The first pre-processing procedure includes an input procedure and a normalization procedure.

The input procedure is the procedure of inputting information of an analog type encrypted image printed on peculiar material such as paper, plastic etc. through the image input unit, or a digital encrypted information from a database .

As an example of this invention, an analog type encrypted image printed on the paper read by the image input unit is digitized, and transferred to a multi step decoding procedure. Therefore, before transferring to the decryption procedure, a normalization procedure correcting input error generated in the input process is needed.

In the normalization procedure, the skew is corrected, the borderline is removed, and the size is corrected.

The skew correcting procedure operates when the inputted image through the image input unit is different from the original skew. If the skew error caused in the input process is not corrected, not only a necessary data area and an unnecessary data area cannot be distinguished, but also it influences on procedures that take place later.

The borderline removing procedure is to exactly extract only the needed encrypted image, and is not an essential component in the invention. The size correcting procedure is the procedure to control the size by the number of minimum blocks required when the encrypted image goes through the decryption procedure. In this case, a size controlling system using a maximum accumulative differential value in a three- dimensional frequency space is used because the interference effect generated in the input of the encrypted image to constituting pixels becomes minimum.

Meanwhile, the security key can be received directly and used in the decryption procedure, or it can be inserted into the encrypted image during the encryption procedure, and transmitted for extraction and decryption, and for the use in the decrypting and restoring procedure.

The second multi step decrypting procedure includes an inverse-puzzling procedure, an inverse-color converting procedure, and a pixel combining procedure, which will be described later, in more details.

The third post-processing procedure is the image correction procedure, which takes in account that among N number colors only p number colors is the righteous color and the rest k number colors are colors used for error correction. In case that the extracted k₀ number colors are smaller than predetermined k number colors, the rest portion is corrected by using a miscellaneous image removing method. Meanwhile, in case there is a miscellaneous image on the image, it may execute a primary restoration procedure through the use of a spatial filtering technique, which has an optimum similarity using information of a neighboring pixel. Further, in case that neighboring pixels are all part of the miscellaneous image, it may execute a secondary restoration procedure of performing an inverse-estimation and a restoration by utilizing a restoration value of the neighboring pixel of the neighborhood.

Next, the detailed technical gist on this invention's decryption method is described as follows.

This invention's decryption method includes procedures of generating a random number map, inverse-puzzling of the encrypted image using the random number map, inverse- converting the color of pixel by using the random number map, and combining the decrypted pixels. Here, the procedure of inverse-converting the color of pixel is not an essential component of this invention, but an additional one.

Further, more description of the above respective procedures will be hereby omitted as this procedure can be easily known by those skilled in this field referring to process operations of each procedure described in detail in the above encryption method.

Fig. 2 is a block diagram of one embodiment for the encryption apparatus on a pixel-by-pixel basis in accordance to this invention.

As shown in Fig. 2, this invention's encryption apparatus is composed of an image input part 21 for converting an analog type information e.g., an original image or a text etc., into digital type, and inputting it, or reading the digital type information stored at a database; a security code input part 22 for inputting a personal peculiar security code; a central processing part 23 performing a multi step encryption by decomposing the input information in a plurality of pixels, puzzling the decomposed pixel using a random number map, changing the position of the pixels irregularly, converting the color of the decomposed pixels irregularly using the random number map; an image storing part 24 storing the information inputted through the image input part 21, as an original image etc., and the encrypted image encrypted in the central processing part 23; an image printing part 25 for printing the encryption image encrypted in the central processing part 23 on a printing such as an identification card, money, bankbook, card etc.; and an image displaying part 26 displaying, on a screen, the encrypted image encrypted in the central processing part 23.

Here, the encryption apparatus may further include a communication part (not shown in . the drawing) for transmitting the encrypted image encrypted in the central processing part 23 to an exclusive decoding apparatus through a communication network. The central processing part 23 is where this invention's encryption method is executed, and its detailed operational description will be provided later, referring to Figs. 4 and 5. The above-mentioned image printing part 25, the image displaying part 26 and the communication part (not shown in the drawing) are the components for outputting the encrypted image. Among them the image displaying part 26 5 and the communication part among them are not essential components, but additional ones.

In case that the above encryption apparatus and method are used, the decoding is impossible without the above mentioned exclusive decoding apparatus. Especially, since

10 in the encrypted image, the color and position of the pixel are changed in the image inputting and converting procedures, an inverse-estimation is impossible because of the characteristic of the computer in which definite numerical values should be compared.

15 On the other hand, the exclusive decoding apparatus can minimize the time to determine forgery and maximize the recognition rate reading the encrypted image information through the image input part, and then, restoring it to the original image according to the decryption algorithm. That

20 is, even though the encrypted image information is partially damaged, the correct recognition rate is maximized by a correction and a restoration of the rest portion. Further, the exclusive decoding apparatus can be embodied for stationary usage and small sized portable

25. usage.

Fig. 3 is a block diagram for one embodiment of the present invention's decryption apparatus on a pixel-by- pixel basis.

As shown in Fig. 3, this invention's decryption

30 apparatus includes an image input part 31 reading the printed encrypted image, or reading digital type encrypted information stored at a database; a security code input part 32 for inputting a personal peculiar security code; a central processing part 33 inverse-puzzling pixels of the

35 inputted encrypted image using a random number map, changing the position of the pixels to the original state, inverse-converting the pixel color of the encrypted image into an original state using the random number map, and performing a multi step decryption, restoring the original image combining the pixels; an image storing part 34 storing the encrypted image, and the decrypted image; and an image displaying part 35 for displaying the decrypted image being able to determine whether there is forgery, of not (the image may be displayed together with the original image). Here, the image-displaying part 35 can be embodied so as to display with the original image.

Here, the decryption apparatus may further include a communication part (not shown in the drawing) for receiving the encrypted image from the encryption apparatus through a communication network. The central processing part 33 is where this invention's decryption method is executed, to restore the encrypted image in real time, and may further execute the function of comparing the original image stored at the database with the decrypted image, being able to determine whether there is forgery or not. Also, it can be equipped with a result-displaying part (not shown in the drawing) displaying the result for the existence and non- existence of the forgery, and it can be also displayed as a part of the image-displaying part 35. Further, in case that the central processing part 33 extracts the encryption key from the encrypted image and then decrypts the encryption key to restore the security code, it is valid to operate without the security code inputting part 32 in the invention. Additional detailed description will be provided later in reference to Figs. 6 and 7.

Also the image input part 31 and the communication part (not shown in the drawing) are the components for the input of the encrypted image, among them, the communication part is not an essential component of this invention, but an additional element.

Fig. 4 is an overall flowchart for one embodiment of an encryption method on a pixel-by-pixel basis in the present invention. In the following description for the encryption method, the parts, which were explained in detail through Fig. 1A to IC will be simplified in this description.

First, input of information such as image or text is done through the image input part in step S401. The image input part converts the analog information (original image or text etc.) into digital, and inputs it, or reads and inputs the digital information from the database.

And then, a security code is inputted through the security code inputting part in step S402. After that, a random number map is generated using a random number generator only or a random number generator with a random number map generator in step S403. At this time, the random number generator can use different algorithms, such as data encryption standard (DES), SEED, etc.

Normalization process is performed executing color control, visibility, threshold, and size control for the inputted image in step S404. In case of receiving digital information, the execution or no execution of the normalization procedure does not influence much upon the encryption procedure.

In the above procedures, either the information input step S401, or the security code input step S402, can be executed first. Also, the random number map generating step S403 and the normalization step S404 can be changed in its executing order. But, the information input step S401 should be prior to the normalization step S404, and the security code input step S402 should be prior to the random number map-generating step S403, for a smooth operation. After that, the normalized image is decomposed into a plurality of pixels in step S405. Decomposing into a plurality of pixels can be done using a variety of methods already introduced. Then, the decomposed pixels go through a multi step encryption in step S406. In the multi step encryption step (S406), the decomposed pixel is puzzled using the random number map, changing its position and color of the decomposed pixel irregularly using the random number map, performing the multi step encryption. Its detailed operation will be described later in reference to Figs. 5A and 5B.

After that, the inputted security code is encrypted to generate an encryption key in step S407, and the generated encryption key is inserted into the encrypted image in step S408. In this invention's encryption method, the encryption key generating and inserting steps S407, S408 are additional factors, and do not have to be performed in the encryption procedure. According to that, in a decryption method to be described later, the encryption key is extracted from the encrypted image, then the encryption key is decrypted and restored for the use of the security code, or the security code is received directly and used in the decryption procedure. The encrypted image is outputted in step S409. At this time, an output system can adopt different methods such as printing on a printing material, storing at a record medium, and transmitting to a decoding apparatus through a communication network. Particularly, among the above output methods printing the encrypted image on a paper of same color background can conceal the encrypted image into the background image. Also it is possible to print specific information on the encrypted image. Then, though the additional specific information may act as little noise in the decryption procedure, it does not influence upon the decrypted image so much since the noise is eliminated in the correction procedure.

Figs . 5A and 5B are flowcharts for one embodiment of the multi step encryption step S406 on a pixel-by-pixel basis in Fig. 4.

First, embodiment shown in Fig. 5A is described as follows .

Primary encryption is performed puzzling the decomposed pixel and changing the position of pixel irregularly using a random number map in step S501, and then, secondary encryption is performed changing the color of the puzzled pixel irregularly using the random number map in step S502.

Second, embodiment shown in Fig. 5b represents that an operational order of the embodiment shown in Fig. 5a is changed, as follows.

Primary encryption is performed changing the color of the decomposed pixel irregularly using the random number map in step S511, and secondary encryption is performed puzzling and changing the position of the pixel irregularly in step S512.

Fig. 6 is an overall flowchart for one embodiment of the decryption method on a pixel-by-pixel basis in this invention. The following decryption procedure will be explained on the basis of a technical gist as its concerned parts can be well known by those skilled in the field referring to process operations of respective procedures, which were described in detail in the encryption method. First, the encrypted image is inputted through the image input part in step S601. At this time, the image input part recognizes the printed encrypted image in digital type; or recognizes the digital type encrypted information stored at a database. The encrypted image may be transferred and inputted from the encryption apparatus through a communication network instead of the image input part.

Subsequently, the normalization of the inputted encrypted image is performed through skew correction, borderline removal and size correction in step S602. In case of receiving digital information, the omission of such normalization step S602 does not influence much upon the decryption procedure.

Then, the encryption key is extracted from the inputted encrypted image in step S603, and the extracted encryption key is decrypted to restore the security code in step S604. Meantime, in case of embodying the invention so as to directly receive the security code through the security code inputting part of the decryption apparatus instead of inserting it into the encrypted image by generating the encryption key in the encryption procedure, the encryption key extraction and security code restoration procedures S603, S604 do not need to be performed.

Herewith, either the encrypted image input step S601 or the security code input step can be executed first, and the normalization step S602 can be executed at any time among procedures from the encrypted image input till the multi step decryption.

Then, the random number map is generated using a random number generator only or by a random number generator with a random number map generator in step S605.

After that, the encrypted image is multi step- decrypted on a pixel-by-pixel basis in step S606. In the multi step decryption step S606, the pixel of the inputted encrypted image is inverse-puzzled using the random number map, to change the position of the pixel to the original state, and the pixel color of the encrypted image is inverse-converted into the original state to perform the multi step decryption using the random number map, and its detailed operation will be later described referring to Figs. 7A and 7B.

The original image is restored combining the decrypted pixel in step S607, and this is an inverse operation of the pixel decomposition step ^"S405 in the encryption method. Then, a miscellaneous image is removed from the restored image to correct the image in step S608. At this time, the correction is executed using an error correction color in the correction step S608. In case that the miscellaneous image exists in the decrypted image, a primary correcting procedure is performed using a spatial filtering technique which uses information of a neighboring pixel and has an optimum similarity, and in case that all of neighboring pixels are part of the miscellaneous image, a secondary correcting procedure is performed by inverse- estimating using a restoration value of the neighboring pixel of the neighborhood. The correcting step S608 is not an essential component, but an additional procedure for improving the quality of the decrypted image.

Then, the corrected image is displayed to determine whether it is forged or not in step S609.

Meanwhile, in the decryption method and before the displaying step S609, it can perform a procedure where the original image stored at the database is compared with the restored image to determine the possibility or forgery, and display the result. Further, before the displaying step S609, it can perform a procedure where the digitized information of the printed information on the encrypted image is compared with the restored information to determine the possibility of forgery and display the result. Furthermore, before the displaying step S609, it can perform a procedure where the digitized information digitized on the printing and the digitized information of the printed information on the encrypted image are compared with the restored information, to decide the possibility of forgery and display the result. Figs. 7A and 7B are flowcharts for one embodiment of the multi step decryption in step S606, executed by processing the encrypted image of Fig. 6 on a pixel-by- pixel basis. First, embodiment of Fig. 7A is described as follows.

Primary decryption is performed inverse-puzzling the pixel of the inputted encrypted image using the random number map, to change the position of the pixel to the original state, in step S701, and secondary decryption is performed by inverse-converting the color of the inverse- puzzled pixel into the original state using the random number map in step S702.

Second, embodiment of Fig. 7B represents that an operational order of the embodiment shown in Fig. 7A, is changed as follows.

Primary encryption is performed inverse-converting the pixel color of the inputted encrypted image into the original state using the random number map in step S711, and then secondary encryption is performed inverse-puzzling the color inverse-converted pixel using the random number map, and changing the position of the pixel to the original state in step S712.

As stated above this invention strengthens more the security and stability provided in a security system (particularly printed security system), what is more it can gain a concealment effect of the encrypted image as a security effect and an optical illusion effect when printed on same color background.

In addition, this invention can be applied to different fields, like identification documents (passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); and paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (certificate of a seal impression, register certified copy etc.), and a card (credit card etc.), and a bankbook, etc.

Also, in the present invention, the encryption/ decryption apparatus and method can be embodied interlocking the encryption apparatus and method and the decryption apparatus and method each other. As this can be embodied by those skilled in the field, more detailed description will be omitted hereby.

This invention's method as above-mentioned, can be embodied as a program and can be stored at a computer readable record, the record medium being CDROM, RAM, ROM, floppy disk, hard disk, optical magnetic disk etc.

Such present invention can be high security-encrypted so as to become almost impossible the decoding without an exclusive decoding apparatus, by performing a multi step encryption of information (image and text etc.) on a pixel by pixel basis according to a random number algorithm and an encryption algorithm.

Additionally, in this invention, an encrypted image is printed in the same color as the background color, making the printing color of the encrypted image and its background color, same, and to thereby heighten a concealment effect, that is, other person can not know where the encryption is . Further, the time taken in determining the possibility of forgery can be minimized, and the encrypted image can be restored in real time.

In addition, a correct recognition rate can be maximized even though the encrypted image information is partially damaged, using a multi-stage image process technique on the rest portion so as to perform a correction and a restoration. This way a stabilized restoration can be provided. Also, the exclusive decoding apparatus can be embodied for stationary usage and a small sized portable usage. Further, this invention can be applied to different fields, like identification documents (passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); and paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (certificate of a seal impression, register certified copy etc.), and a card (credit card etc.), and a bankbook, etc. It will be apparent to those skilled in the field that substitution, modifications and variations can be made in the present invention without deviating from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A method for encrypting an image on a pixel-by- pixel basis, comprising the steps of: a) receiving information to be encrypted; b) generating a random number map; c) decomposing the information into a plurality of pixels; d) encrypting the pixels and generating encrypted information; and e) outputting the encrypted information.

2. The method as recited in claim 1, wherein said step d) performs a multi step encryption including a position converting procedure which changes a position of the pixel and a color converting procedure which changes a color of the pixel using the random number map.

3. The method as recited in claim 2, wherein said step d) includes the step of: dl) primary encryption puzzling the pixel using the random number map, changing the position of the pixel and generating a puzzled pixel; and d2 ) secondary encryption converting the color of the puzzled pixel using the random number map.

4. The method as recited in claim 2, wherein said step d) includes the steps of: dl ) primary encryption converting the color of the pixel using the random number map and generating a color converted pixel; and d2 ) secondary encryption puzzling the color converted pixel using the random number map, and changing the position.

5. The method as recited in claim 1, wherein said step d) performs an encryption changing a position of the pixel using the random number map.

6. The method as recited in claim 5, wherein said step d) performs an encryption puzzling a position of the pixel using the random number map.

7. The method as recited in claim 2, wherein the color converting procedure performs an encryption converting the color of the pixel into a background color group, to thereby print the encrypted information in the same color as the background color of the printing material.

8. The method as recited in claim 2, wherein the color converting procedure performs an encryption converting the color of the pixel into one color group.

9. The method as recited in claim 8, wherein the color group has a yellow group.

10. The method as recited in claim 2, wherein the color converting procedure performs an encryption converting the color of the pixel into a numerous the color groups.

11. The method as recited in any claim among claims 1 through 10, further comprising the step of f) performing an encryption executing color control, visibility, threshold and size control of the image to be encrypted for normalization.

12. The method as recited in any claim among claims 1 through 10, further comprising: f) encrypting an inputted security code and generating an encryption key; and g) inserting the generated encryption key into the encrypted information.

13. The method as recited in any claim among claims 1 through 10, wherein said step a) comprises: al ) receiving the information to be encrypted, such as image or text; and a2 ) receiving a security code.

14. The method as recited in claim 13, wherein said step al) includes the step of converting the information to be encrypted from analog information to digital information.

15. The method as recited in claim 13, wherein said step al) includes the step of reading digital information.

16 The method as recited in any claim among claims 1 through 10, wherein the random number map is generated by using only a random number generator.

17. The method as recited in any claim among claims 1 through 10, wherein the random number map is generated by using a random number generator and a random number map generator.

18. The method as recited in any claim among claims 1 through 10, wherein said step e) includes the step of printing the encrypted information on printing.

19. The method as recited in claim 18, wherein the printing includes identification documents (e.g., passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (e.g., certificate of a seal impression, register certified copy etc.); a card (credit card etc.); and a bankbook.

20. The method as recited in claim 18, wherein said step e) further includes the step of printing particular information on the printings on which the encrypted information is printed.

21. The method as recited in claim 18, wherein said step e) further includes the step of representing the encrypted information on a display unit.

22. The method as recited in any claim among claims 1 through 10, wherein said step e) includes the steps of: transmitting the encrypted information to an external device.

23. The method as recited in any claim among claims 1 through 10, wherein said step e) includes the step of storing the encrypted information at a record medium.

24. A method for decrypting an image on a pixel-by- pixel basis, comprising the steps of: a) receiving an encrypted information; b) gaining a security code used for decoding the encrypted information; c) generating a random number map; d) decrypting the encrypted information on a pixel by pixel basis and generating decrypted pixels; e) combining the decrypted pixels and generating a restored information; and f) outputting the restored information.

25. The method as recited in claim 24, wherein said step d) performs a multi step decryption including a position converting procedure which inverse-changes a position of pixel of the encrypted information and a color converting procedure which inverse-changes a color of the pixel of the encrypted image using the random number map.

26. The method as recited in claim 25, wherein said step d) includes the steps of: dl) primary decryption by inverse-puzzling the pixel of the encrypted information using the random number map, changing the position of the pixel and generating an inverse-puzzled pixel; and d2 ) secondary decryption by inverse-converting the color of the inverse-puzzled pixel using the random number map.

27. The method as recited in claim 25, wherein said step d) includes the steps of: dl) primary decryption by inverse-converting the pixel color of the encrypted information using the random number map and generating an inverse-converted pixel; and d2 ) secondary encryption by inverse-puzzling the color of the inverse-converted pixel using the random number map, and changing the position of the pixel.

28. The method as recited in claim 24, wherein said step d) includes the step of performing a decryption by inverse-changing a position of a pixel of the encrypted information using the random number map.

29. The method as recited in claim 28, wherein said step d) includes the step of performing a decryption by inverse-puzzling the position of the pixel of the encrypted information using the random number map.

30. The method as recited in any claim among claims 24 through 29, -further comprising the step: g) performing normalization through skew correction, border line removal and size correction of the encrypted information.

31. The method as recited in any claim among claims 24 through 29, further comprising the step: g) performing correction of the restored information by eliminating miscellaneous image from the restored information.

32. The method as recited in claim 31, wherein said step g) includes the steps of: gl) performing a primary restoration by utilizing a spatial filtering technique having an optimum similarity in which information of neighboring pixel is used, in case there is a miscellaneous image on the restored information; and g2 ) performing a secondary restoration executing an inverse-estimation and restoration using a restoration value of the neighboring pixel of the neighborhood in case that all the neighboring pixels are part of the miscellaneous image.

33. The method as recited in any claim among claims 24 through 29, further comprising the step: h) comparing the original image stored in a database with the restored information, determining whether there is forgery or not, and displaying its result.

34. The method as recited in any claim among claims 24 through 29, further comprising the step: h) comparing the digitized information of the additional information printed on the encrypted information, with the restored information, and determining whether there is forgery or not, and displaying its result.

35. The method as recited in any claim among claims 24 through 29, further comprising the step: h) comparing the digitized information from other information on the printing, with the restored information, determining whether there is forgery or not, and displaying its result.

36. The method as recited in any claim among claims 24 through 29, further comprising the step: h) outputting the restored information and also representing the original image .

37. The method as recited in any claim among claims 24 through 29, wherein said step a) including the step of reading the encrypted image printed on a printing in digital type.

38. The method as recited in claim 37, wherein the printing includes identification documents (e.g., passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (certificate of . a seal impression, register certified copy etc.); a card (credit card etc.); and a bankbook.

39. The method as recited in any claim among claims 24 through 29, wherein said step a) includes the step of reading the encrypted information, which is digital information stored in a record medium.

40. The method as recited in any claim among claims 24 through 29, wherein said step a) includes the step of receiving the encrypted image from an encryption apparatus .

41. The method as recited in any claim among claims 24 through 29, wherein said step b) includes the steps of: bl) extracting an encryption key from the encrypted information; and b2 ) decrypting the encryption key and restoring the security code.

42. The method as recited in any claim among claims 24 through 29, wherein said step b) includes the step of receiving the security code through a security code inputting part.

43. The method as recited in any claim among claims 24 through 29, wherein the random number map is generated by using only a random number generator.

44. The method as recited in any claim among claims 24 through 29, wherein the random number map is generated by using a random number generator and a random number map generator.

45. An apparatus for encrypting an image on a pixel by pixel basis, comprising: an input unit for receiving information to be encrypted; a security code input unit for receiving a security code; an encryption unit for decomposing the information into a plurality of pixels and for encrypting the pixels, thereby generating an encrypted information; a storing unit for storing the encrypted information; and an output unit for outputting the encrypted information.

46. The apparatus as recited in claim 45, wherein said encryption unit performs multi step encryption changing the position and the color of the pixels using a random number map.

47. The apparatus as recited in claim 46, wherein the multi step encryption performs a primary encryption puzzling the pixel using the random number map, and changing a position of the pixel, and after that, a secondary encryption converting a color of the puzzled pixel using the random number map.

48. The apparatus as recited in claim 46, wherein the multi step encryption performs a primary encryption converting a color of the pixel using the random number map, and after that, a secondary encryption puzzling a color converted pixel using the random number map and changing the position of the pixel.

49. The apparatus as recited in claim 45, wherein said encryption unit performs an encryption changing a position of the pixel using the random number map.

50. The apparatus as recited in claim 49, wherein said encryption unit performs an encryption puzzling a position of the decomposed pixel using the random number map.

51. The apparatus as recited in claim 46, wherein the color converting procedure converts the color of the pixel into a background color group, to thereby print the encrypted information by the same color group as a background color of a printing.

52. The apparatus as recited in claim 46, wherein the color converting procedure converts the color of the pixel into a color group.

53. The apparatus as recited in claim 52, wherein the color group has a yellow group.

54. The apparatus as recited in claim 46, wherein the color converting procedure converts the color of the pixel into a numerous color groups.

55. The apparatus as recited in any claim among claims 45 through 54, wherein said encryption unit further performs an encryption executing color control, visibility, threshold, and size control of the information to be encrypted for normalization.

56. The apparatus as recited in any claim among claims 45 through 54, wherein said encryption unit further executes a function of generating an encryption key encrypting the inputted security code, and after that, of inserting the encryption key into the encrypted information.

57. The apparatus as recited in any claim among claims 45 through 54, wherein said input unit converts the information to be encrypted, which is analog information, such as text or image, into digital information.

58. The apparatus as recited in any claim among claims 45 through 54, wherein said input unit reads digital information to be encrypted, such as text or image, which is stored at the record medium.

59. The apparatus as recited in any claim among claims 45 through 54, wherein said output unit includes a printing unit for printing the encrypted information on printing material.

60. The apparatus as recited in claim 59, wherein the printing includes identification documents (e.g., passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (e.g., certificate of a seal impression, register certified copy etc.); a card (credit card etc.); and a bankbook.

61. The apparatus as recited in claim 59, wherein said printing unit further performs a function of printing specific information on the printing on which the encrypted information is printed.

62. The apparatus as recited in any claim among claims 45 through 54, wherein said output unit includes a displaying unit for displaying the encrypted information .

63. The apparatus as recited in any claim among claims 45 through 54, wherein said output unit includes a communication unit for transmitting the encrypted information to an external device.

64. An apparatus for decrypting an image on a pixel by pixel basis, comprising: an input unit for receiving an encrypted information; a security code obtaining unit for gaining a security code; a decryption unit for decrypting the encrypted information on a pixel by pixel basis, combining the decrypted pixels, and generating restored information; a storing unit for storing the restored information; and an output unit for outputting the restored information.

65. The apparatus as recited in claim 64, wherein said decryption unit performs a multi step decryption including a position converting procedure which inverse-changes a position of pixel of the encrypted information and a color converting procedure which inverse-changes a color of pixel of the encrypted information received through the input unit using the random number map.

66. The apparatus as recited in claim 65, wherein the multi step decryption includes a primary decryption inverse-puzzling the pixel of the inputted encrypted information using the random number map, changing the position of the pixel, and generating an inverse-puzzled pixel, and after that, a secondary decryption inverse- converting the color of the inverse-puzzled pixel using the random number map.

67. The apparatus as recited in claim 65, wherein the multi step decryption includes a primary decryption inverse-converting the color of the pixel of the encrypted image using the random number map, and generating a color inverse-converted pixel and after that, a secondary decryption inverse-puzzling the color inverse-converted pixel using the random number map, and changing the position of the pixel.

68. The apparatus as recited in claim 64, wherein the decryption unit performs a decryption by inverse-changing the position of the pixel of the encrypted information received through the input unit using the random number map.

69. The apparatus as recited in claim 68, wherein the decryption unit performs a decryption by inverse-puzzling the pixel of the encrypted information received through the input unit using the random number map.

70. The apparatus as recited in any one claim among claims 64 through 69, wherein said decryption unit further performs normalization through skew correction, border line removal and size correction .of the encrypted information.

71. The apparatus as recited in any claim among claims 64 through 69, wherein said decryption unit further performs correction procedure of the restored information removing miscellaneous image from the restored information.

72. The apparatus as recited in claim 71, wherein the correction procedure includes the steps of: performing a restoration using a spatial filtering technique having an optimum similarity in which information of neighboring pixel is used, in case that the restored information has the miscellaneous image; and performing an inverse-estimation and restoration using a restoration value of the neighboring pixel of the neighborhood in case that all the neighboring pixels are part of miscellaneous image.

73. The apparatus as recited in any claim among claims 64 through 69, wherein said decryption unit further performs a function of comparing an original image stored in a database with the restored information, determining whether there is forgery or not, and transferring its result to the output unit.

74. The apparatus as recited in any claim among claims 64 through 69, wherein said decryption unit further performs a function of comparing digitized information from the information printed on the encrypted information, with the restored information, and determining whether there is forgery or not, and transferring its result to the output unit.

75. The apparatus as recited in any claim among claims 64 through 69, wherein said decryption unit further executes a function of comparing digitized information from other information on the printing with the restored information, and determining whether there is forgery or not, and transferring its result to said output unit.

76. The apparatus as recited in any claim among claims 64 through 69, wherein said output unit outputs the restored information and also the original image.

77. The apparatus as recited in any one claim among claims 64 through 69, wherein said input unit reads, in digital type, the encrypted information, which is printed on the printing.

78. The apparatus as recited in claim 77, wherein the printing includes identification documents (e.g., passport, identification card, driver's license, student identification card, public official identification card, medical insurance card etc.); paper money, bill, securities, gift certificate, membership card, and various certificates issued by government and municipal offices (e.g., certificate of a seal impression, register certified copy etc.); a card (e.g., credit card etc.); and a bankbook.

79. The apparatus as recited in any claim among claims 64 through 69, wherein said input unit reads the encrypted image, which is digital information stored at a record medium.

80. The apparatus as recited in any claim among claims 64 through 69, wherein said input unit receives the encrypted information from an encryption apparatus .

81. The apparatus as recited in any claim among claims 64 through 69, wherein said security code obtaining unit extracts an encryption key from the encrypted information, and then, decrypts the encryption key, and restores the security code.

82. The apparatus as recited in any claim among claims 64 through 69, wherein said security code obtaining unit is a security code input part for receiving the security code.

83. A method for encrypting/decrypting an image on a pixel-by-pixel basis, comprising the steps of: a) receiving an information to be encrypted; b) generating a random number map for a encryption; c) decomposing the information to be encrypted into a plurality of pixels; d) performing multi step encryption by changing a position and a color of the pixel using the random number map for the encryption, and generating encrypted information; e) outputting the encrypted information; f) receiving the encrypted information; g) gaining a security code for decoding the encrypted information; h) generating a random number map for a decryption; i) performing a multi step decryption by inverse- changing a position and a color of the pixel of the encrypted information using the random number map for the decryption; j ) restoring an original image by combining the decrypted pixels and generating a restored information; and k) outputting the restored information.

84. An apparatus for encrypting/decrypting an image on a pixel-by-pixel basis, said apparatus comprising: an input unit for receiving encrypted information and information to be encrypted; a security code input unit for receiving a security code for an encryption; a multi step encryption unit for multi step encryption by decomposing the information into a plurality of pixels, and changing a position and a color of the pixel using a random number map for an encryption; a security code obtaining unit for gaining a security code for a decryption; a multi step decryption unit for multi step decryption by inverse-changing the position and the color of the pixel of the encrypted image using the random number map, and then, restoring an original image by combining the decrypted pixels and generating restored information; a storing unit for storing the encrypted information and the restored information; and an output unit for outputting the encrypted image and the restored information.

85. A computer readable recording medium storing instructions for executing a method for encrypting an image on a pixel by pixel basis in an encryption apparatus equipped with a processor, said method comprising the steps of: a) receiving information to be encrypted; b) generating a random number map; c) decomposing the information into a plurality of pixels; d) encrypting the pixels and generating encrypted information; and e) outputting the encrypted information.

86. The computer readable record medium as recited in claim 85, the method further comprising the step of f) performing normalization though color control, visibility, threshold and size control of information to be encrypted.

87. The computer readable record medium as recited in claim 85 or 86, the method further comprising the steps of: g) encrypting an inputted security code and generating an encryption key; and h) inserting the generated encryption key into the encrypted information.

88. A computer readable recording medium storing instructions for executing a method for decrypting an image on a pixel-by-pixel basis in a decryption apparatus equipped with a processor, the method comprising the steps of: a) receiving an encrypted information; b) gaining a security code used for decoding the encrypted information; c) generating a random number map; d) decrypting the encrypted information on a pixel by pixel basis and generating decrypted pixels; e) combining the decrypted pixels and generating a restored information; and f) outputting the restored information.

89. The computer readable record medium as recited in claim 88, the method further comprising step g) performing normalization through skew correction, border line removal and size correction of the encrypted information.

90. The computer readable record medium as recited in claim 88 or 89, the method further comprising the step of h) performing correction of the image removing a miscellaneous image from the restored image.

91. A computer readable recording medium storing instructions for executing a method for encrypting/decrypting an image on a pixel-by-pixel basis, in an encryption/ decryption apparatus equipped with a processor, the method comprising the steps of: a) receiving an information to be encrypted; b) generating a random number map for a encryption; c) decomposing the information to be encrypted into a plurality of pixels; d) performing multi step encryption by changing a position and a color of the pixel using the random number map for the encryption, and generating encrypted information; e) outputting the encrypted information; f) receiving the encrypted information; g) gaining a security code for decoding the encrypted information; h) generating a random number map for a decryption; i) performing a multi step decryption by inverse- changing a position and a color of the pixel of the encrypted information using the random number map for the decryption; j ) restoring an original image by combining the decrypted pixels and generating a restored information; and k) outputting the restored information.