JP5115930B2 - An image information encryption method, an image information encryption device, and a computer program for image encryption. - Google Patents

Description

  In recent years, as the computerization of society progresses, attempts have been made to digitize various functions, while ensuring the confidentiality of the digitized information has become a problem. In order to ensure the confidentiality of computerized information, attempts have been made to limit access to the computerized information using so-called biometric personal information unique to individuals, such as fingerprints, irises, and vein patterns. However, this information itself is often information that should be kept secret, and such information also needs to be encrypted.

As a method for encryption, there are methods such as a common key cryptosystem and a public key cryptosystem. For example, the following Non-Patent Document 1 discloses a so-called RSA cipher as a public key cryptosystem.
R. Rivest et al., “A method for obtaining digital signatures and public-key cryptosystems”, Communications of the ACM, Vol. 21, no. 2, pp120-126, 1978

  However, the technique described in Non-Patent Document 1 is complicated, and it is desired to perform encryption by a simpler method.

  In view of the above problems, an object of the present invention is to provide a simpler image information encryption method, an image information encryption apparatus using the image information encryption method, and a computer program for realizing the method.

  The inventors of the present invention have made extensive studies in view of the above problems, and by performing non-integer order Fourier transform on image information data, the order can be used as a key. Focusing on the fact that the original image can be acquired by using the method, the present invention has been completed.

  That is, an image information encryption method according to one means of the present invention is characterized in that non-integer order Fourier transform is performed on image information data.

  According to another aspect of the present invention, there is provided an image information encryption device, an image information data storage unit for storing image information data, and a key generation for generating a key by performing non-integer order Fourier transform based on the image information data. Part.

  According to another aspect of the present invention, there is provided a computer program comprising: an image information data storage unit that stores image information data in a computer; and a key generation that performs a non-integer order Fourier transform based on the image information data to generate a key. It functions as a means.

  As described above, according to the present invention, it is possible to provide a simpler image information encryption method, an image information encryption apparatus using the image information encryption method, and a computer program for realizing the method.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention can be implemented in many different forms, and is not limited only to the description of the following embodiments and examples. .

  The present embodiment relates to an image information encryption apparatus (hereinafter referred to as “the present encryption apparatus”), and FIG. 1 is a functional block diagram of the encryption apparatus. The encryption device 1 according to the present book includes an image information data storage unit 11 that stores image information data, and a key generation unit 12 that performs non-integer order Fourier transform based on the image information data and generates a key.

  The encryption apparatus can store a computer program for executing encryption in a recording medium such as a hard disk of an information processing apparatus such as a so-called personal computer, and can function as an encryption apparatus by actually executing the program. it can. Therefore, in addition to the above configuration, a monitor for displaying necessary information such as an image, a CPU for performing calculation processing, a memory for temporarily storing data necessary for calculation by the CPU, and information through a telecommunication line It is preferable to have what is generally required for information processing, such as a modem for transmitting and receiving data including.

  In this encryption apparatus, the image information data storage unit 11 stores image information data. The image information that is the basis of the stored image information data is preferably two-dimensional image information such as a fingerprint, an iris, and a vein pattern, but is not limited thereto.

In this encryption apparatus, the key generation unit 12 performs a non-integer order Fourier transform based on the image information data to generate a key. Here, the non-integer order Fourier transform is preferably performed by, for example, the following equation. In the following formula, u (x) is an input function, and p is an order.

  In this non-integer order Fourier transform, the order p can be a key.

  Here, specific processing of the encryption apparatus will be described. Here, a case where a human fingerprint is used as image information will be described as an example. FIG. 2 shows an example of a fingerprint image.

  This fingerprint image information is grasped as a set of data including the x coordinate (position in the row direction), the y coordinate (position in the column direction) and the luminance (for example, an integer value between 0 and 255), and is a two-dimensional image. It is stored in the image information data storage unit 11 as information data.

Next, the key creation unit 12 performs non-integer order Fourier transform on each row of the image information data (non-integer order Fourier transform in the row direction). At this time, the key generation unit 12 uses the degree p as an encryption key. This key is necessary for performing the non-integer order Fourier transform, and can be randomly generated by the key generation unit 12 and used as a key. However, the input data can be the order. 3 shows the luminance distribution of each pixel in Line 1 in FIG. 2, and FIGS. 4 and 5 show the result after the non-integer order Fourier transform. In FIG. 3, the horizontal axis represents the x coordinate, and the vertical axis represents the luminance. In FIG. 4, the horizontal axis represents the _xp coordinate, and the vertical axis represents the amplitude. Further, in FIG. 5, the horizontal axis represents the _xp coordinate, and the vertical axis represents the phase. In the non-integer order Fourier transform performed here, the order p may be the same for each row, but may be different for each row. If they are the same, it is possible to simplify the key, and it is possible to improve the encryption by making it different for each row.

  Further, in this encryption apparatus, it is preferable to perform non-integer order Fourier transform for each column on this result from the viewpoint of advanced encryption. In this case, the orders in the non-integer order Fourier transform may be the same or different. If they are the same, it becomes possible to simplify the key, and it is possible to further enhance the encryption by making it different for each row.

  As a result, encrypted image information data can be created. By using this image information and key, inverse non-integer order Fourier transform can be performed and decoded.

  In the present embodiment, each pixel is described as a so-called black and white image whose intensity is only, but for example, it is grasped as a luminance distribution for each color such as red (R), green (G), blue (B), It can also be applied to color images.

  As described above, this encryption apparatus can provide a simpler image information encryption method, an image information encryption apparatus using the same, and a computer program for realizing the image information encryption apparatus.

  Moreover, although this encryption apparatus is realizable using a computer as above-mentioned, it can also encrypt optically. Specifically, out of the two-dimensional information corresponding to the image information, light including information for one row or one column is transmitted through at least one lens arranged at a predetermined distance, and the row of the transmitted light complex amplitude or This is possible by acquiring the sequence as encrypted image information. This acquired encrypted image information can be stored as data in a recording medium such as a hologram. In this case, the distance between the light source of image information before encryption and the center of the lens, the distance between the center of the lens and the acquisition position of the encrypted image information, and the focal length of the lens can be used as keys (for example, FIG. 6). reference).

  The present invention has industrial applicability as an image information encryption method, an image information encryption device, and a computer program therefor.

It is a figure which shows the functional block of the image information encryption apparatus which concerns on embodiment. It is a figure which shows the fingerprint image information as an example of image information. It is a conceptual diagram about the luminance distribution of Line1 in FIG. It is a conceptual diagram (amplitude distribution) about the result of having performed the non-integer order Fourier transform with respect to the luminance distribution of Line1 in FIG. It is a conceptual diagram (phase distribution) about the result of having performed the non-integer order Fourier transform with respect to the luminance distribution of Line1 in FIG. It is a conceptual diagram about the method to optically encrypt.

Claims (4)

An image information data storage unit that stores image information data including a set of data including x-coordinate that is position information in the row direction, y-coordinate that is position information in the column direction, and luminance ;
A non-integer order Fourier transform based on the image information data to generate a key, and an image information encryption device comprising :
The non-integer order Fourier transform is represented by the following formula, and the order p is a key,
An image information encryption apparatus that varies the order p for each row.
  The image information encryption apparatus according to claim 1, further comprising a non-integer order Fourier transform for each column.
On the computer,
Image information data storage means for storing image information data comprising a set of data including x-coordinate that is position information in the row direction, y-coordinate that is position information in the column direction, and luminance ;
A computer program for image information encryption for functioning as a key generation means for performing a non-integer order Fourier transform based on the image information data and generating a key ,
The non-integer order Fourier transform is represented by the following formula, and the order p is a key,
A computer program for encrypting image information in which the order p is varied for each row.
4. The computer program according to claim 3, further comprising a non-integer order Fourier transform for each column.