JP2000010481A - Hidden information processing method and apparatus therefor as well as recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processing method for hidden information having high concealability by adding a signal indicating the hidden information in the stage when the first processing of a plurality of fractional transform processing ends and the last processing is not yet completed. SOLUTION: An input section 2 inputs the signal of a real domain indicating an image which is original information to an FRFT section 4 which executes two-dimensional FRFT of the input signal with a degree (a). A signal indicating a watermark information from a watermark input section 8 is added to this output signal by an addition section 6. The added output signal is subjected to two-dimensional FRFT with a degree (b) by an FRFT section 10 and is outputted through an output section 12. The watermark information is hidden in mid-way of Fourier transform and, therefore, the disclosure thereof by ordinary Fourier transform or inverse Fourier transform does not occur and the concealability is high. Even if a third person attempts to view the watermark information by FRFT or iFRFT, the level of the signal indicating the watermark information is adequately selected, by which the watermark information may be invisible with a slight difference in the degree of iFRFT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hidden information processing method, a hidden information processing method, and a recording medium, and more particularly, to a signal representing original information, a signal representing hidden information being added and distributed, and the distribution information representing the original information. The present invention relates to a hidden information processing method and apparatus for detecting a signal representing hidden information accompanying a signal, and a storage medium storing information including hidden information.

[0002]

2. Description of the Related Art Hidden information is added to electronic information distributed through communication, recording media, and the like as a measure for preventing unauthorized duplication or as a clue for post-survey, since it is generally easy to duplicate. Hidden information does not appear in a normal information use state, but can be revealed only by special means, and is also called a digital watermark.

For music information, video information, and the like, a signal representing the information is transformed into a real domain by transform processing such as Fourier transform.
It is known that the signal of (in) is converted into a signal of a transform domain such as a frequency domain, a digital watermark is inserted in the transform domain, and the information is returned to the information of the real domain by inverse transform processing such as inverse Fourier transform and distributed. ing.

[0004]

In the above-described hidden information processing method, the hidden information in the real domain is highly confidential, but once the information is transferred to the transform domain, the hidden information is immediately exposed. Confidentiality is not sufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a hidden information processing method and apparatus with high concealment of hidden information, and a recording method for recording hidden information with high confidentiality. The realization of the medium.

[0006]

Means for Solving the Problems (1) According to a first invention for solving the above-mentioned problems, a signal representing hidden information is added to a signal representing original information and distributed, and the original information is represented at a distribution destination. A hidden information processing method for detecting a signal representing the hidden information accompanying a signal, wherein the signal representing the original information is converted from a signal in a real domain to a signal in a transform domain by serial combination of a plurality of fractional transform processes. And expressing the hidden information in a signal representing the original information at a stage where at least a first fractional transform process has been processed and at least a final fractional transform process has not been processed among the plurality of fractional transform processes. This is a hidden information processing method characterized by adding a signal.

(2) According to a second aspect of the present invention, a signal representing hidden information is added to a signal representing original information to distribute the signal, and the hidden destination is accompanied by the signal representing the original information at a distribution destination. A hidden information processing method for detecting a signal representing information, wherein the signal representing the original information is converted from a real domain signal to a transform domain signal by a serial combination of a plurality of fractional transform processes, A signal representing the hidden information is added to a signal representing the original information at a stage where at least the first fractional transform processing has been processed and at least the last fractional transform processing has been processed among the plurality of fractional transform processing, Transform domain signals into multiple inverse fractional transforms Inverse conversion to a real domain signal by serial combination of at least the first inverse fractional transform processing of the plurality of inverse fractional transform processing has been processed and at least the last inverse fractional transform processing has not been processed. Detecting a signal representing the hidden information in a step.

(3) According to a third aspect of the present invention, a signal representing original information is added with a signal representing hidden information to distribute the signal, and the hidden destination is accompanied by the signal representing the original information at a distribution destination. A hidden information processing apparatus for detecting a signal representing information, a conversion means for transforming the signal representing the original information from a signal of a real domain to a signal of a transform domain by a serial combination of a plurality of fractional transform processes. Adding a signal representing the hidden information to a signal representing the original information at a stage where at least a first fractional transform process has been processed and at least a final fractional transform process has not been processed among the plurality of fractional transform processes. And a hidden information adding unit.

(4) According to a fourth aspect of the present invention, a signal representing hidden information is added to a signal representing original information to distribute the signal, and the hidden signal to which the signal representing the original information accompanies a distribution destination. A hidden information processing apparatus for detecting a signal representing information, a conversion means for transforming the signal representing the original information from a signal of a real domain to a signal of a transform domain by a serial combination of a plurality of fractional transform processes. Adding a signal representing the hidden information to a signal representing the original information at a stage where at least a first fractional transform process has been processed and at least a final fractional transform process has not been processed among the plurality of fractional transform processes. Hidden information adding means, and a plurality of inverse fractions for converting the transform domain signal. Inverse transforming means for performing an inverse transform to a signal of a real domain by a serial combination of the first and second inverse fractional transform processes, and at least a first inverse fractional transform process of at least a first inverse fractional transform process has been performed among the plurality of inverse fractional transform processes Detecting means for detecting a signal representing the hidden information at a stage where the transform processing is not yet performed.

(5) According to a fifth aspect of the present invention, a signal representing original information converted from a signal in a real domain into a signal in a transform domain by a serial combination of a plurality of fractional transform processes is provided. A signal representing hidden information added to a signal representing original information at a stage where at least a first fractional transform process has been processed and at least a final fractional transform process has not been processed among the plurality of fractional transform processes. A recording medium characterized by the following.

[0011] In any one of the first to fifth inventions, it is preferable that the transform domain is a frequency domain and the fractional transform is a fractional Fourier transform. This is preferred.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of a hidden information processing system. This system is an example of an embodiment of a hidden information processing device of the present invention. The configuration of the present system shows an example of the embodiment of the device of the present invention. The operation of the system provides an example of an embodiment of the method of the present invention.

The configuration of the present system will be described. As shown in FIG. 1, the present system has an input unit 2. The input unit 2 receives a signal representing original information such as an image to be distributed, for example, an image. Note that the original information is not limited to image information. For example, music information, character information, etc.
Of course, it may be so-called multimedia information.

The signal representing the original information input through the input unit 2 is input to the FRFT unit 4.
The FRFT unit 4 performs a fractional Fourier transform (FRFT) on an input signal. The fractional Fourier transform is an example of the embodiment of the fractional transform in the present invention.

[0015] FRFT is described, for example, in the document D. Mendlovic an.
d HM Ozaktas, "Fractional Fourie transforms and
their optical implementation: Part I, "J. Opt. So
c. Am. A, Vol. 10, pp. 1875-1881, 1993.

In general terms, the usual Fourier transform is

[0017]

(Equation 1)

Where FRFT is

[0019]

(Equation 2)

## EQU1 ## Here, the order a is a real number. That is, the order a can take fractional or decimal values. This is a fractional (fractional)
This is why it is called.

The FRFT of order a and the FRFT of order b can be performed in series (cascade), in which case the following relationship is established.

[0022]

(Equation 3)

Here, when a + b = 1, the result is the same as a normal Fourier transform. By utilizing this relationship,
A normal Fourier transform can be performed by serial operation of a plurality of FRFTs.

As a technique for performing the FRFT at a high speed, a discrete fractional Fourier transform (Discrete
fractional Fourie transform: DFRFT) is described, for example, in the literature HM Ozaktas et.al., "Digital Computation
of the Fractional Fourie Transform, "IEEE, Transac
tions on Signal Processing, Vol.44, pp.2141-2150,
It is known as described in 1996.

[0025] The FRFT unit 4 uses an order a smaller than 1 for the input signal according to, for example, the DFRFT method.
Is to be performed. Since the input signal is a signal representing an image, the FRFT unit 4 performs a two-dimensional FRFT.

The output signal of the FRFT unit 4 is added by the adding unit 6 to a signal of the real domain representing the watermark information given from the watermark input unit 8. Watermark information is an example of an embodiment of hidden information in the present invention. The part consisting of the adder 6 and the watermark input 8 is
It is an example of embodiment of hidden information addition means in the present invention.

As the watermark information, for example, text information indicating the attribution of intellectual property rights such as copyright is used. However, the present invention is not limited to this, and may be an appropriate figure or pattern which can identify the source of the original information. good. The signal level of the watermark information (lev
el) indicates that the effect on the reproduced image described later is S / N (signa
of the output signal of the FRFT unit 4 as well as within the allowable range of
The setting within the N limit is preferable in that it makes it difficult to illegally decode the watermark information described later.

The output signal of the FRFT unit 4 to which the signal of the real domain representing the watermark information is added is input to the FRFT unit 10. The FRFT unit 10 includes, for example, a DF
According to the RFT method, FRFT is performed on an input signal with an order b smaller than one. The sum of the order a and the order b is 1. FRFT unit 4 and FRFT unit 10
The portion consisting of is an example of an embodiment of the conversion means in the present invention.

By the serial FRFT processing by the FRFT unit 4 and the FRFT unit 10, a complete Fourier transform is performed on the signal representing the original information, and the signal in the real domain representing the original information is converted into a signal in the frequency domain. The frequency domain is an example of the embodiment of the transform domain in the present invention. On the other hand, regarding the signal of the real domain representing the watermark information, the FRFT unit 10
As a result of T, that is, an incompletely Fourier-transformed signal is obtained.

Such a signal is output through the output unit 12. The output of the signal by the output unit 12 is performed on a recording medium such as a DVD (digital video disck). The recording medium can be an example of the embodiment of the recording medium in the present invention. The recording medium is D
Not limited to VD, CD (compact disk) and PD (p
Other types of optical recording (storage) media, such as a hot disk, a magnetic storage medium or a semiconductor storage medium may be used. Such a recording (storage) medium is provided for distribution. Hereinafter, a recording medium will be used as a representative, but it will also include a storage medium.

The output may be performed not only to the recording medium but also to the demand side on demand through a communication line. Regardless of whether the signal is distributed through a recording medium or communication, it is preferable to appropriately compress the signal from the viewpoint of improving the efficiency of recording or communication.

The reading unit 14 reads a signal of a recording medium obtained at a distribution place or a signal obtained by communication. If the read signal is a compressed signal, it is decompressed in the reading unit 14.

The output signal of the reading unit 14 is transmitted to the iFRFT unit 16
To be entered. The iFRFT unit 16
For an input signal, a two-dimensional inverse fractional Fourie transform (iFRF)
T). The order of iFRFT is b
It is. The output signal of the iFRFT unit 16 is input to the iFRFT unit 18. iFRFT section 18
Is designed to perform two-dimensional iFRFT on an input signal in order a. The sum of the order a and the order b is 1. iFRFT
The portion composed of the section 16 and the iFRFT section 18 is an example of an embodiment of the inverse transform means in the present invention.

IFRFT section 16 and iFRFT section 18
, The read signal is subjected to an inverse Fourier transform, and is converted from a frequency domain signal to a real domain signal. The signal in the real domain is input to the reproducing unit 20. The reproducing unit 20 reproduces an image based on the input real domain signal.

The output signal of the iFRFT unit 16 is also input to the watermark detection unit 22. The watermark detection unit 22 is an example of an embodiment of a detection unit according to the present invention. The watermark detecting unit 22 detects watermark information included in the input signal. Since the signal representing the watermark information is FRFTed from the real domain by the order b in the FRFT unit 10 and included in the read signal, i
The signal is converted into a signal in the real domain by being subjected to iFRFT in the order b in the FRFT section 16. That is, the watermark information is restored. The output signal of the watermark detection unit 22 is provided to the display unit 24 and displayed as a detection result.

Next, the operation of the present system will be described. The input unit 2 outputs a real domain signal representing an image as original information to F
Input to the RFT unit 4. The FRFT unit 4 performs a two-dimensional FRFT on the input signal with the order a. The addition unit 6 adds a signal representing watermark information from the watermark input unit 8 to the output signal of the FRFT unit 4. The output signal of the FRFT unit 4 to which the signal representing the watermark information is added is subjected to a two-dimensional FRFT by the order b by the FRFT unit 10 and output (distributed) through the output unit 12.

The reading unit 14 reads a signal obtained at a distribution place. The read signal is 2 in the order b by the iFRFT unit 16.
Dimensional iFRFT, and two-dimensional iFRFT with order a in the iFRFT unit 18 to convert the signal into a signal in the real domain,
The image is reproduced by the reproduction unit 20 as an image. In parallel,
The watermark detection unit 22 detects the watermark information included in the output signal of the iFRFT unit 16 and displays the detection result on the display unit 24.

[0038] If the watermark signal is detected from the source of the recording medium or the source of the received signal that is not legitimate, it is evidence that unauthorized duplication has been performed. Further, the fact that watermark information is not detected from information disguised as a legitimate source or source can also prove fraud.

Since the watermark information is hidden in the middle of the Fourier transform using the characteristics of the FRFT, the watermark information is not exposed or revealed by ordinary Fourier transform or inverse Fourier transform, and the confidentiality is high. Also, if the third party is FRFT or i
Even if the user tries to view the watermark information by the FRFT, the level of the signal representing the watermark information can be made invisible by selecting the level of the signal representing the watermark information as described above, since the order of the iFRFT can be made slightly different to make the order of the FRFT secret. By doing so, it is possible to maintain the difficulty of revealing the watermark information.

Also, the two-dimensional signal in the FRFT stage has the property of a hologram, and is less susceptible to signals of other stages having different orders, so that signals of other stages having different orders are not affected. Is strong against an unauthorized operation such as deleting the watermark information by adding.

For normal users who do not particularly need to detect watermark information, the iFRFT units 16 and 18 are used.
May be replaced by an iFT unit 26 that performs an inverse Fourier transform, as shown in FIG. 2, for example. This is preferable in that the configuration of the information reproducing apparatus for the user is simplified.

The above is an example in which the Fourier transform and the inverse Fourier transform are used as a method for performing bidirectional signal transform between the real domain and the transform domain. The domain transform is performed by the Fourier transform and the inverse Fourier transform. Not limited, for example, cosine conversion,
It goes without saying that other appropriate transforms that are reversible and can be fractionated, such as sine transform and Hilbert transform, may be used.

Also, an example has been described in which information is distributed in the form of a signal in a transform domain in a storage medium or through communication. However, the information may be distributed in a form returned to a signal in a real domain. Of course.

[0044]

As described above in detail, according to the present invention, it is possible to realize a hidden information processing method and apparatus with high concealment of hidden information and a recording medium on which high confidential hidden information is recorded. Can be.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a block diagram of another configuration of a part of the device according to the exemplary embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 2 input unit 4, 10 FRFT unit 6 adder unit 8 watermark input unit 12 output unit 14 reading unit 16, 18 iFRFT unit 20 playback unit 22 watermark detection unit 24 display unit 26 iFT unit

Claims (5)

[Claims] 1. A hidden information processing method for adding a signal representing hidden information to a signal representing original information and distributing the signal, and detecting a signal representing the hidden information accompanied by the signal representing the original information at a distribution destination. The signal representing the original information is converted from a real domain signal to a transform domain signal by a serial combination of a plurality of fractional transform processes, and at least the first fractional transform among the plurality of fractional transform processes is performed. A hidden information processing method, comprising: adding a signal representing the hidden information to a signal representing the original information at a stage where the form processing has been processed and at least the last fractional transform processing has not been performed. 2. A hidden information processing method for adding a signal representing hidden information to a signal representing original information and distributing the signal, and detecting a signal representing the hidden information accompanied by the signal representing the original information at a distribution destination. The signal representing the original information is converted from a real domain signal to a transform domain signal by a serial combination of a plurality of fractional transform processes, and at least the first fractional transform among the plurality of fractional transform processes is performed. Adding a signal representing the hidden information to a signal representing the original information at a stage where the form processing has been processed and at least the final fractional transform processing has not been performed; and converting the signal of the transform domain into a plurality of inverse fractional transform processings. Of real domain by serial combination of And a signal representing the hidden information is detected at a stage where at least the first inverse fractional transform process has been processed and at least the last inverse fractional transform process has not been processed among the plurality of inverse fractional transform processes. A hidden information processing method. 3. A hidden information processing apparatus for adding a signal representing hidden information to a signal representing original information and distributing the signal, and detecting a signal representing the hidden information accompanied by the signal representing the original information at a distribution destination. Converting means for converting the signal representing the original information from a signal of a real domain to a signal of a transform domain by a serial combination of a plurality of fractional transform processes; and at least a first of the plurality of fractional transform processes. Hidden information adding means for adding a signal representing the hidden information to a signal representing the original information at a stage where the fractional transform processing has been processed and at least the last fractional transform processing has not been performed. Hidden information processing device. 4. A hidden information processing apparatus that adds a signal representing hidden information to a signal representing original information and distributes the signal, and detects a signal representing the hidden information accompanied by the signal representing the original information at a distribution destination. Converting means for converting the signal representing the original information from a signal of a real domain to a signal of a transform domain by a serial combination of a plurality of fractional transform processes; and at least a first of the plurality of fractional transform processes. A hidden information adding means for adding a signal representing the hidden information to a signal representing the original information at a stage where the fractional transform processing has been processed and at least the last fractional transform processing has not been processed; and Serial combination of multiple inverse fractional transform processes Inverse transform means for inversely transforming the signal into a real domain signal, wherein at least a first inverse fractional transform process of the plurality of inverse fractional transform processes has been processed and at least a final inverse fractional transform process has not been performed. And a detecting means for detecting a signal representing the hidden information. 5. A signal representing original information obtained by converting a signal of a real domain into a signal of a transform domain by a serial combination of a plurality of fractional transform processes, and at least a first fractional of the plurality of fractional transform processes. A recording medium characterized by recording a signal representing hidden information added to a signal representing original information at a stage where the transform processing has been processed and at least the last fractional transform processing has not been performed.