JP4144469B2 - Digital watermark verification apparatus and digital watermark verification method - Google Patents

Description

  The present invention relates to a technique for limiting image quality deterioration due to digital watermark embedding in a specific area (important area) by limiting embedding of digital watermark information in a partial area of an image in the digital watermark technique for embedding information in an image. Is.

  In recent years, illegal copying, falsification, and theft of digital contents have become a problem. In order to prevent these problems, a digital watermark technique has been developed that embeds additional data such as a digital signature, copyright information, and a message while adding minute processing that cannot be perceived to the content. With digital watermarking technology, additional data is integrated into the content itself, and it is used to prevent tampering, illegal duplication, and unauthorized transfer without increasing the storage capacity when uncompressed.

  There are two methods of embedding an electronic watermark, such as a method that is easily broken by alteration and cannot be detected, and a method that is not easily detected by alteration. Fragile digital watermarks are used for tamper detection and the like, and digital watermarks that are not easily broken are used for copyright protection. Hereinafter, a fragile digital watermark is referred to as a “fragile digital watermark”, and a hard-to-break digital watermark is referred to as a “robust digital watermark”.

  In a fragile digital watermark used for image alteration detection, an electronic signature is embedded as additional data in an image, and alteration is detected by a mismatch of signature values between the embedding side and the verification device. For example, when embedding a fragile digital watermark in a bitmap image, as shown in FIG. 32, a bit plane other than the LSB (when strictly verifying, a bit brain other than the LSB and all not used for embedding the LSB Hash value is calculated from this bit), and the hash value (electronic signature) encrypted by the public key cryptosystem is embedded in the LSB as additional data. Normally, the embedding position in the LSB is randomized using a pseudo-random sequence using a key as a seed.

  When the image is verified by this method, as shown in FIG. 33, the embedded position is determined from the LSB portion of the image embedded with the electronic signature in the same procedure as that for embedding, and the embedded data is extracted. The hash value generated at the time of embedding the digital watermark is decrypted from the extracted data. Also, a hash value is calculated from the portion other than the LSB by the same algorithm as that on the embedding side, and the decrypted hash value is compared. As a result of comparison, if the hash values match, it can be seen that the image has not been altered. Normally, the bit length of the hash value generated compared to the image data is very short (for example, in the case of the hash algorithm called SHA1, the output data is 160 bits regardless of the input data length). If there is a slight change in the image due to the characteristics of the hash operation, the generated hash value will be completely different. Therefore, if even one pixel is altered by comparing the hash values, tampering will occur. Can be detected.

  Further, if the range for calculating one hash value is not the entire image but a range divided by M × N pixel size blocks in the image, it is possible to detect alteration of the image in units of M × N blocks. , It is possible to specify the tampering location in the image in units of blocks.

  In some fragile digital watermarks, hash values and signature data are embedded in coefficients in a frequency space after wavelet transform, discrete cosine transform (DCT), quantization, and the like. These methods are also basically the same as digital watermarking for bitmaps, in which the hash value calculation target and signature data embedding target are simply replaced with the coefficients after frequency conversion from the image data itself. The detection method is the same as that of the bitmap.

  In addition, there are other methods such as changing the coordinates of the hash calculation target and the embedding target, and these also use the same detection method.

  However, in the conventional digital watermark technology, the entire image is slightly deteriorated due to a slight change for embedding additional data. Therefore, it could not be used in applications that require lossless medical images.

  In the technique disclosed in Japanese Patent Application Laid-Open No. 2003-115989 (Patent Document 1), an important area is set in an image, and additional data is not embedded in the important area. It is carried out. This important area can be set directly by the user, or an important area based on the ROI (Region of Interest) function of JPEG2000, which is a new still image compression standard, can be used.

JP 2003-115989 A

  However, in the technique disclosed in Patent Document 1, if important area information is deleted, synchronization for reading digital watermark data cannot be obtained, and reading of additional data embedded in the entire image becomes impossible. There is. In other words, in the above technique, an electronic signature for detecting falsification of an image is created from the entire image including the important area and embedded in a portion excluding the important area, thereby realizing lossless of the important area. In this case, if the important area information is deleted, the electronic signature cannot be detected correctly, so that not only the important area but also the entire image is falsified, and a message embedded in the entire image cannot be extracted. There is a problem such as.

  In addition, the technique disclosed in Patent Document 1 avoids embedding additional data in important area information, and embeds additional data for an important area in a portion other than other important areas. When embedding data outside the important area, the data embedding format other than the important area changes, and (2) the embedding order of the data has changed. In addition, the additional data of the part other than the important area cannot be correctly decoded, the entire image is falsified, and the message extraction sometimes fails.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to be able to correctly decode additional data in a portion other than the important area even if important area information is added / deleted. The embedded message can be extracted correctly, and when alteration is detected, the areas that have become important areas or areas that are no longer important areas are detected as falsifications by falsification of the important area information. capable of identifying the tampered position of the portion other than to provide a new and improved electronic watermark verification equipment Contact and watermark verification method.

In order to solve the above problems, according to a first aspect of the present invention, in the digital watermark verification apparatus, an image input terminal (10) to which image data of a target image for verifying the digital watermark is input, and the input image A blocking unit (200) that divides data into blocks of a predetermined size, and an important area information input terminal (11) to which important area information regarding whether each block belongs to an important area or a non-important area is input , a unit that is blocked, in accordance with the important area information, from the critical region without extracting the signature data (to identify the embedded position in the same manner as when embedding the signature data) from the non-critical areas around the important area and signature extractor for extracting the signature data of the non-critical area (201), in the units blocked, signature generation unit for generating signature data (202), signature A signature comparison unit (203) that compares the signature data extracted by the extraction unit (201) with the signature data generated by the signature generation unit (202), and a comparison result output that outputs a comparison result by the signature comparison unit (203) and a terminal (12), the comparison result output of the signature comparison unit (203) is, the electronic watermark verification and wherein the input to the signature extraction portion (201) of Ru is provided.

  According to such a digital watermark verification apparatus, it is possible to detect falsification of an image output by the digital watermark embedding apparatus having the above-described excellent effects.

  In the digital watermark verification apparatus of the present invention, the following applications are possible.

Signature extraction section, the important region blocks judged as alteration does not match the signature data by the signature comparator unit, but it may also be so regarded as unimportant region blocks. By extracting the signature data and extracting the message by regarding the important area block determined to be falsified as the non-important area block,
(G) When the important area information is falsified and changed from the non-important area to the important area, the changed area can be detected not as falsification but as a change in the area information.
(H) The probability that all messages can be correctly extracted regardless of the addition of important area information is increased.

Also, the signature extraction portion (201), a non-critical region blocks judged as alteration does not match the signature data by the signature comparator unit (203), but it may also be so considered important area block. By extracting nonsignificant area blocks that have been determined to be falsified as important area blocks and extracting signature data from the surrounding nonimportant areas,
(I) When the important area information is altered and changed from the important area to the non-important area, the changed area can be detected not as tampering but as the area information is changed.

Also, the signature extraction portion (201) from the region enclosed by the blocks by the important area signed flag embedded in the non-critical regions have been shown to have the signature data for the important region, estimates the importance area but it may also be so. As a result,
(J) The important area information becomes unnecessary.

To solve the above problems, according to the second aspect of the present invention, there is provided an electronic watermark verification method, the image input unit, an image input step of image data of the target image to verify the electronic watermark is input, Blocking step for dividing the input image data into blocks of a predetermined size by the blocking means , and important area information regarding whether each block belongs to the important area or the non-important area by the important area information input means. Significant area and non-important area signature data is extracted from surrounding non-important areas without extracting signature data from the important areas according to the important area information in the input important area information input process and in blocks. and signature extraction step of extracting the signature extracting means, in the units blocked, a signature generation step of generating signature data by the signature generating means, And signature data extracted in the name extracting step, a signature comparing step of comparing the signature data generated in the signature generation step, the comparison result by the sign comparing step, seen including a comparison result outputting step of outputting the comparison result output means , using the comparison result output of the signature comparison process, characterized that you perform signature extraction process again, the electronic watermark verification method is Ru is provided.

  According to this digital watermark verification method, it is possible to detect falsification of an image output by the digital watermark embedding method that exhibits the above-mentioned excellent effects.

  The following application is possible in the digital watermark verification method of the present invention.

Signature extracting means, in the signature extraction process, the critical domain block signature data is determined to be falsified does not match the signature comparing step, but it may also be so regarded as unimportant region blocks. By extracting the signature data and extracting the message by regarding the important area block determined to be falsified as the non-important area block,
(G) When the important area information is falsified and changed from the non-important area to the important area, the changed area can be detected not as falsification but as a change in the area information.
(H) The probability that all messages can be correctly extracted regardless of the addition of important area information is increased.

Also, the signature extracting means, in the signature extraction process, a non-critical region block signature data is determined to be falsified does not match the signature comparing step, but it may also be so considered important area block. By extracting nonsignificant area blocks that have been determined to be falsified as important area blocks and extracting signature data from the surrounding nonimportant areas,
(I) When the important area information is altered and changed from the important area to the non-important area, the changed area can be detected not as tampering but as the area information is changed.

Also, the signature extracting means, in the signature extraction process, from the region enclosed by the blocks by the important area signed flag embedded in the non-critical regions have been shown to have the signature data for the important region, the important area but it may also be estimated. As a result,
(J) The important area information becomes unnecessary.

  In the above description, the reference numerals in parentheses attached to the constituent elements are merely shown as examples of corresponding constituent elements in the embodiments and drawings described below for easy understanding. It is not limited to.

  As described above, according to the present invention, even if important area information is added / deleted, it is possible to correctly decode the additional data in a portion other than the important area, and to correctly extract the embedded message. In addition, when tampering is detected, it is possible to detect areas that have become important areas or areas that are no longer important areas by tampering with important area information, etc., and identify the tampering positions of other parts. It is.

  Exemplary embodiments of a digital watermark embedding device, a digital watermark verification device, a digital watermark embedding method, and a digital watermark verification method according to the present invention will be described below in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

(First embodiment)
A digital watermark embedding device, a digital watermark verification device, a digital watermark embedding method, and a digital watermark verification method according to this embodiment will be described. First, the configuration of the digital watermark embedding device will be described.
FIG. 1 is an explanatory diagram showing the configuration of the digital watermark embedding apparatus according to the first embodiment. FIG. 2 is an explanatory diagram showing a case where the digital watermark embedding apparatus of FIG. 1 is applied to a JPEG2000 compressor.

  As shown in FIG. 1, the digital watermark embedding apparatus according to the present embodiment includes an image input terminal 1 for inputting image data, and block formation for dividing the image data input from the image input terminal 1 into blocks. Section 100, important area information input terminal 2 for inputting important area information, signature generation section 101 for generating signature data from the blocked image data, and signature embedding section for embedding signature data obtained from signature generation section 101 102 and an image output terminal 3 for outputting the image data after the signature data is embedded.

  When the digital watermark embedding apparatus shown in FIG. 1 is applied to a JPEG2000 compressor, as shown in FIG. 2, a color conversion unit 50 that converts a color space in the case of a color image, and a wavelet conversion that performs wavelet conversion. A unit 51, a quantization unit 52 that quantizes wavelet coefficients, and an encoding unit 53 that encodes digital watermark-embedded coefficients and important region information. Then, the image output terminal 3 outputs a bit stream of the image in which the digital watermark is embedded.

Next, the configuration of the digital watermark verification apparatus will be described.
FIG. 3 is an explanatory diagram showing the configuration of the digital watermark verification apparatus according to this embodiment. FIG. 4 is an explanatory diagram showing a case where the digital watermark verification apparatus of FIG. 3 is applied to a JPEG2000 decompressor.

  As shown in FIG. 3, the digital watermark verification apparatus includes an image input terminal 10 for inputting image data, a block forming unit 200 that divides image data input from the image input terminal 10 into blocks, An important area information input terminal 11 for inputting area information, a signature extraction unit 201 for extracting a signature embedded by the digital watermark embedding apparatus, a signature generation unit 202 for generating signature data from the blocked image data, and extraction A signature comparison unit 203 that compares the generated signature with the generated signature and a comparison result output terminal 12 that outputs the comparison result are provided.

  In addition, when the digital watermark verification apparatus of FIG. 3 is applied to a JPEG2000 decompressor, as shown in FIG. 4, a decoding unit 204 that further decodes the JPEG2000 bitstream and outputs wavelet coefficients and important region information is provided. Composed.

  The digital watermark embedding device and the digital watermark verification device according to the present embodiment are configured as described above. Next, operations of the digital watermark embedding device and the digital watermark verification device will be described.

First, the operation of the digital watermark embedding apparatus will be described.
The image data of the target image in which the digital watermark is embedded is input to the image input terminal 1. When the digital watermark is directly embedded in the pixel data, the input data is pixel data. In the case of digital watermarking in the frequency space, it is a wavelet coefficient or a DCT coefficient.

  Image data input to the image input terminal 1 is passed to the blocking unit 100. The blocking unit 100 divides the input image data into blocks of a predetermined size (M × N size). In the case of digital watermarking to pixel data, it becomes a block of M × N pixels, and in the case of digital watermarking in the frequency space, it is a block of M × N coefficients in the coefficient space after wavelet transform or DCT. Become. This block may be composed of coefficient groups having different frequencies and indicating the same position in the pixel space, or may be composed of coefficient groups having the same frequency and indicating a close position in the pixel space.

  As illustrated in FIG. 5, the signature generation unit 101 generates signature data in units that are blocked by the blocking unit 100. As the signature data, a hash value obtained by using a hash function such as SHA1 as a block coefficient, a hash value encrypted by RSA or a part of the hash value, or the like is used. The generated signature data is used to verify tampering of the generation source block.

FIG. 6 is an explanatory diagram showing an example of signature data generation for a block.
As shown in FIG. 6, the signature data may be obtained by collecting a plurality of blocks and obtaining a hash value and dividing it by the number of blocks, or by concatenating hash values for a plurality of blocks. Also, different methods or values generated in different area units may be combined.

  The signature embedding unit 102 embeds signature data obtained from the signature generation unit 101 in each block obtained from the blocking unit 100. For embedding the signature data, as shown in FIG. 5, the signature data generated from each block may be embedded in the generation source block. In this case, since the portion used for generating signature data cannot be used for embedding signature data, signature data is generated from a portion other than the portion used for embedding. The block for generating signature data and the block for embedding signature data may be different blocks.

FIG. 7 is an explanatory diagram showing the relationship between embedded data and embedded positions.
As shown in FIG. 7, the embedding position in the block can be scrambled by a pseudo-random sequence or a replacement table.

FIG. 8 is an explanatory diagram showing the signature embedding relationship between the important area and the unimportant area when the important area is used.
Coordinate information set as an important area in the image data is input to the important area information input terminal 2. As shown in FIG. 8, the operation of the signature embedding unit 102 for the important area and the non-important area for embedding the important area signature data is as follows.
(1) The signature data in the important area is not embedded in the important area.
(2) The signature data in the important area is embedded in the surrounding non-important area.
(3) The signature data of the important area is embedded in the non-important area in addition to the signature data of the non-important area.

  The signature data of the important area embedded in the non-important area can be embedded in the non-important area block for each important area block. In addition, all the signature data in all important areas can be linked and divided into non-important areas to be embedded.

  The signature data of the important area may be embedded only in a specific non-important area, or may be embedded only in non-important area blocks around the important area as shown in FIG.

  FIG. 10 is a flowchart illustrating an example of an embedding process when embedding signature data in an important area only in non-important area blocks around the important area. In this example, three types of pseudo-random sequences (or replacement tables) A, B, and C are used.

  First, a pseudo random sequence A is initialized (step S301). Then, the block to be embedded next is determined by the pseudo random sequence A (step S302). It is determined whether the block determined in step S302 is an important area block or a non-important area block (step S303). If it is an important area block, the process returns to step S302 again.

  If the block determined in step S302 is a non-important region block, the pseudo-random sequence C is initialized by the pseudo-random sequence B (step S304), and then the non-important region block is described as described below. The signature data of the non-important area and the signature data of the important area are embedded in order.

  First, the signature data of the non-important area is embedded. First, the embedding position is determined by the pseudo random sequence C (step S305). Then, the signature data of the non-important area is embedded in the determined embedding position (step S306). Steps S305 to S306 are repeated until the embedding in the block is completed (step S307). When the embedding of the signature data of the non-important area in the block is completed, the signature data of the important area is then embedded. First, the embedding position is determined by the pseudo random sequence C (step S308). Then, the signature data of the important area is embedded at the determined embedding position (step S309). Steps S309 to S310 are repeated until the embedding in the block is completed (step S311).

  It is determined whether or not all data embedding is completed in the block (step S311). If there is still embedding data, the above steps S301 to S310 are repeated, and the process is terminated when all the data embedding is completed. .

FIG. 11 is an explanatory diagram showing an outline of the signature embedding position.
When the signature data is embedded in the non-important area, the embedding order is as shown in FIG. FIG. 11A shows a case where important area signature data is not embedded, and FIG. 11B shows a case where important area signature data is embedded. The signature data for the non-important area is embedded so that the position does not change regardless of the existence of the important area. For this reason, the presence or absence of important area information does not affect the presence or absence of non-important area blocks. The embedding position may be scrambled as shown in FIG.

  In addition, in order to detect tampering strictly, when creating signature data from all except the embedding position, as shown in FIG. 12, first, the important area signature data is embedded, and then the non-important area block signature is embedded. Embed the data.

FIG. 13 is an explanatory diagram showing the digital watermark embedding apparatus in this case.
As shown in FIG. 13, the switching unit 20 switches to the contact B when generating the non-important area block signature for embedding the important area signature data, and switches to the contact A in other cases. When a non-important area block signature for embedding the important area signature data is generated, the following processing flow is performed.
(1) Connect the switching unit 20 to the contact A.
(2) The signature generation unit 101 generates signature data for the important area.
(3) The signature embedding unit 102 embeds the signature data for the important area in the non-important area block.
(4) Connect the switching unit 20 to the contact B.
(5) The signature embedding unit 102 passes the non-important area block in which the important area signature data is embedded to the signature generation unit 101.
(6) The signature generation unit 101 generates a non-important area block signature.
(7) As shown in FIG. 12, the non-important area block signature data is embedded in the block in which the important area signature data is embedded.

  The image output terminal 3 outputs the image data after the signature data is embedded.

The operation of the digital watermark embedding apparatus has been described above.
Next, the operation of the digital watermark verification apparatus will be described.

  The image data of the target image for verifying the digital watermark is input to the image input terminal 10. When the digital watermark is directly embedded in the pixel data, the input data is pixel data. In the case of digital watermarking in the frequency space, it is a wavelet coefficient or a DCT coefficient.

  Image data input to the image input terminal 10 is passed to the blocking unit 200. The blocking unit 200 divides the input image data into blocks of a predetermined size (M × N size as in the digital watermark embedding side). In the case of digital watermarking to pixel data, it becomes a block of M × N pixels, and in the case of digital watermarking in the frequency space, it is a block of M × N coefficients in the coefficient space after wavelet transform or DCT. Become.

  The signature extraction unit 201 extracts signature data embedded in the image data. The extraction is performed by determining the embedding position by the same method as that for embedding signature data, and extracting data from the embedded position. If multiple signatures are combined or divided on the digital watermark embedding side, the reverse processing is performed to generate the original signature. In the case where the hash value or the like is encrypted on the digital watermark embedding side, the encryption is decoded here, returned to the original data, and passed to the signature comparison unit 203. At the time of extraction, the important area information input from the important area information input terminal 11 is used, and the signature data is not extracted from the important area. Instead, it is embedded from the non-important area by the same method as that for embedding the digital watermark. Specify the location and extract the signature data.

  The signature generation unit 202 generates signature data in units that are blocked by the blocking unit 200. The generation is performed by the same method as the digital watermark embedding side. However, when encryption or the like is used on the digital watermark embedding side, it is not necessary to perform encryption here, and the signature extraction unit 201 decodes the encryption. The signature generation unit 202 passes the generated signature data to the signature comparison unit 203.

  The signature comparison unit 203 compares the signature data of the signature extraction unit 201 and the signature generation unit 202. Blocks with the same signature data are not tampered with, and blocks that do not match are tampered with.

(A) When the important area information set on the digital watermark embedding side is not set The signature extraction of the non-important area block is the same regardless of the setting of the important area. Therefore, tampering can be detected regardless of the presence or absence of an important area.
The signature data of the block subjected to the digital watermark embedding process as the important area block is embedded in the non-important area block, but since there is no important area information, the signature data is tried to be extracted from the important area block itself. However, since the obtained signature data has random values, the important area block is detected as a falsified block.

(B) When important area information not set on the digital watermark embedding side is set The signature extraction of the non-important area block is the same regardless of the setting of the important area. Therefore, tampering can be detected regardless of the presence or absence of an important area.
The signature data of the block set as the important area block is originally embedded in the block itself as a non-important area block. However, since it is set as an important area block, it tries to extract signature data from surrounding non-important areas. However, since the signature data obtained is a random value, the important area and the set part are detected as tampered blocks.

  The comparison result by the signature comparison unit 203 is output from the comparison result output terminal 12.

(Effects of the first embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(A) Tampering verification can be performed on important areas without loss.
(B) Even when important area information is deleted, the important area can be detected as a falsified area without being falsified entirely, and the position of another falsified block can be specified.
(C) Even when the important area information is given, it is possible to detect the part of the important area as a falsified area without identifying the whole area, and to specify the position of another falsified block.

(Second Embodiment)
FIG. 14 is an explanatory diagram showing the configuration of the digital watermark embedding apparatus according to the second embodiment. The digital watermark embedding apparatus according to the first embodiment shown in FIG. 13 further includes a message input terminal 5.

  FIG. 15 is an explanatory diagram of a configuration of the digital watermark verification apparatus according to the second embodiment. The digital watermark detection apparatus according to the first embodiment shown in FIG. 3 further includes a message output terminal 13.

  Next, operations of the digital watermark embedding device and the digital watermark verification device according to the present embodiment will be described. First, the operation of the digital watermark embedding apparatus will be described.

  The signature embedding unit 102 embeds the message input from the message input terminal 5 in each block. In the case of a block in which a message is embedded, in a case where tampering is detected in detail, the signature generation unit 101 generates signature data from the message embedded data after the message is embedded.

16 and 17 are explanatory diagrams showing message embedding positions.
As the message embedding position, for example, as shown in FIG. 16, the message size to be embedded is embedded. As a result, the signature data for the important area following the message can be acquired. Further, for example, as shown in FIG. 17, there is a method of embedding a flag or offset of the message start position. In this case, even when the non-important area block is tampered and the message size cannot be extracted correctly, the signature data for the important area can be correctly extracted, and erroneous detection of the important area can be reduced.

  In addition, it is possible to improve the data extraction resistance at the time of tampering by fixing the embedding position of the message and signature data and embedding the synchronization flag in each field.

Since other operations are substantially the same as the operations of the first embodiment, a duplicate description is omitted.
Next, the operation of the digital watermark verification apparatus will be described.

The signature extraction unit 201 extracts the message embedded on the digital watermark embedding side and outputs it from the message output terminal 13. The embedding position of the message and signature data is determined by the same method as that for the digital watermark embedding side.
Since other operations are substantially the same as the operations of the first embodiment, a duplicate description is omitted.

(A) When the important area information set on the digital watermark embedding side is not set In the case of the message embedding position shown in FIG. 16, the message in the non-important area can be correctly extracted regardless of the presence or absence of the important area. In the important area part, no message is embedded, but sometimes a random message can be extracted. This can be discarded by error correction coding or by giving an electronic signature or hash value to the message itself.

In the case of the message embedding position shown in FIG. 17, the message in the non-important area can be correctly extracted regardless of the presence or absence of the important area. Even if the non-important area block is tampered with, the important area signature data can be extracted if the embedded area of the important area signature data is not tampered.
In the important area, nothing is embedded, but a random message may be extracted. This can be discarded by error correction coding or by giving an electronic signature or hash value to the message itself.

(B) When the important area information not set on the digital watermark embedding side is set In the case of the message embedding position shown in FIGS. 16 and 17, the message in the non-important area is correct regardless of the presence or absence of the important area. Can be extracted. For the newly set important area part, the message is not extracted because the message is not extracted from the important area at the time of verification.

(Effect of the second embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(D) A message embedded in a non-important area can be correctly extracted regardless of the presence / absence of important area information.

(Third embodiment)
FIG. 18 is an explanatory diagram of a configuration of the digital watermark embedding device according to the third embodiment. The electronic watermark embedding apparatus according to the second embodiment shown in FIG. 14 further includes a message dividing unit 110.

  FIG. 19 is an explanatory diagram of a configuration of the digital watermark verification apparatus according to the third embodiment. The digital watermark detection apparatus according to the second embodiment shown in FIG. 15 further includes a message combining unit 210.

  Next, operations of the digital watermark embedding device and the digital watermark verification device according to the present embodiment will be described. First, the operation of the digital watermark embedding apparatus will be described.

  The message dividing unit 110 divides the message input from the message input terminal 5 up to the number of blocks to be embedded. At the time of division, address information indicating which part of the original message is the message after each division is stored. The address information may be anything that can restore the original position, such as the number of bytes from the beginning of the message, the number of bytes in the divided message, and an index indicating the position of the divided message.

FIG. 20 is an explanatory diagram showing an embedded message dividing method in units of blocks.
As shown in FIG. 20, header information is added to the head of each divided message. Address information indicating the message position is stored in the header information. In addition, an error detection code such as cyclic redundancy check (CRC) may be stored. The CRC may be assigned in fine units such as several bytes. In addition, the original message itself may have error resistance using error correction coding or repetition.

Other operations are substantially the same as the operations of the second embodiment, and thus redundant description is omitted.
Next, the operation of the digital watermark verification apparatus according to this embodiment will be described.

FIG. 21 is an explanatory diagram showing a message combining method.
As shown in FIG. 21, the message combining unit 210 reads the header information of the extracted message and determines the position in the entire original message. If an error detection code such as CRC is included in the header, the message that detected the error is discarded.

Combining messages extracted from all blocks to compose the entire original message.
Other operations are substantially the same as the operations of the second embodiment, and thus redundant description is omitted.

(A) When the important area information set on the digital watermark embedding side is not set The message of the non-important area block can be correctly extracted regardless of the presence or absence of the important area. For the original important area block, a message is not embedded, but a random message may be extracted. As shown in FIG. 22, the original data can be restored by discarding it by putting CRC in the header, by performing error correction coding on the entire message, or by repeating data and majority processing.

(B) When important area information not set on the digital watermark embedding side is set The message of the non-important area block can be correctly extracted regardless of the presence or absence of the important area.

  Since the message is not extracted for the newly set important area, the message is lost. As shown in FIG. 22, the original data can be restored by performing error correction coding on the entire message or by repeating data and voting.

(Effect of the third embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(E) All messages can be correctly extracted regardless of the presence or absence of important area information.
(F) All messages can be correctly extracted regardless of addition / deletion of important area information.

(Fourth embodiment)
FIG. 23 and FIG. 24 are explanatory diagrams showing the configuration of the digital watermark verification apparatus according to the fourth embodiment. The digital watermark verification apparatus shown in FIG. 23 is configured to input the comparison result output of the signature comparison unit 203 to the signature extraction unit 201 with respect to the digital watermark verification apparatus according to the first embodiment shown in FIG. It is characterized by that. The digital watermark verification apparatus shown in FIG. 24 is configured to input the comparison result output of the signature comparison unit 203 to the signature extraction unit 201 with respect to the digital watermark verification apparatus according to the second embodiment shown in FIG. It is characterized by that.

  The operation of the digital watermark verification apparatus according to this embodiment will be described.

  The signature extraction unit 201 extracts the signature data and the message by regarding the important area block determined to be falsified by the signature comparison unit 203 as the non-important area block.

  The signature data obtained from the signature extraction unit 201 and the signature data obtained from the signature generation unit 202 are compared, and if they match, no alteration is made. In this case, the change from the non-important area to the important area may be notified.

  In addition, as shown in FIG. 25, when embedding a digital watermark, non-important area block identification information is embedded in each block, and if this information can be extracted from the important area block, it is regarded as an unimportant area block. Information can also be extracted. As the non-important area block identification information, a value obtained by a pseudo random sequence, a fixed value, a value obtained from coordinates, or the like can be used. However, since the signature data in the important area cannot be changed, the data cannot be changed so as to avoid it even if the value is accidentally the same value as the non-important area identification code. For this reason, it is impossible to determine whether or not the area was originally an unimportant area by using only the non-important area block identification information. For this reason, it is necessary to extract signature data and the like. However, if the non-important area block information does not match, the extraction process can be stopped before extracting the signature.

  Other operations are substantially the same as the operations of the first and second embodiments, and thus redundant description is omitted.

(Effect of the fourth embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(G) When the important area information is falsified and changed from the non-important area to the important area, the changed area can be detected not as falsification but as a change in the area information.
(H) The probability that all messages can be correctly extracted regardless of the addition of important area information is increased.

(Fifth embodiment)
The configuration of the digital watermark verification apparatus according to this embodiment is substantially the same as that of the digital watermark verification apparatus according to the fourth embodiment shown in FIG.

  The operation of the digital watermark verification apparatus according to this embodiment will be described.

  The signature extraction unit 201 regards the non-important area block determined to be falsified by the signature comparison unit 203 as the important area block, and extracts the signature data from the surrounding non-important areas. The target block to be extracted is determined by a method similar to the method for determining the position when the signature data of the important area is embedded. For example, when embedding a digital watermark, signature data is embedded in order from the non-important area block adjacent to the right edge of the important area to the non-important areas around the important area in the clockwise direction. The important area is estimated with the selected block, and signature data is extracted clockwise from the non-important area block at the right end of the estimated important area.

  The signature data obtained from the signature extraction unit 201 and the signature data obtained from the signature generation unit 202 are compared, and if they match, no alteration is made. In this case, the change from the important area to the non-important area may be notified.

  In addition, as shown in FIG. 26, an important area signature data flag may be embedded in each block at the time of embedding a digital watermark. In this case, if there is no important area signature data, a flag indicating that there is no important area signature data is stored, and if there is important area signature data, a flag indicating that there is important area signature data is stored. .

  If there is a block that is flagged that there is signature data for important area from around the falsified block in the non-important area, the falsified block is regarded as the important area and Tamper detection is performed using the signature data for critical areas.

  Other operations are substantially the same as the operations of the fourth embodiment, and a duplicate description is omitted.

(Effect of 5th Embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(I) When the important area information is altered and changed from the important area to the non-important area, the changed area can be detected not as tampering but as the area information is changed.

(Sixth embodiment)
27 and 28 are explanatory diagrams illustrating the configuration of the digital watermark verification apparatus according to the sixth embodiment. The digital watermark verification apparatus according to the present embodiment is characterized in that the important area information input terminal 11 is deleted from the digital watermark verification apparatus according to the fourth embodiment shown in FIGS. .

The operation of the digital watermark verification apparatus according to this embodiment will be described.
The signature extraction unit 201 extracts the signature data using the non-important area method regardless of the important area / non-important area.

  The information altered by the signature comparison unit 203 is passed to the signature extraction unit 201.

FIG. 29 is an explanatory diagram showing the operation of the present embodiment.
As shown in FIG. 29, the signature extraction unit 201 extracts an important area signature flag (see FIG. 26) embedded in a block that has not been tampered with, and estimates an important area. For example, when a tampered block is surrounded by an area block indicated by the important area signature flag to have a signature for the important area, the tampered block enclosed in the block may be regarded as an important area. In addition, since there is actually alteration, an area block indicated as having an important area signature in the important area signature flag may not be circularly closed. In this case, the falsified block and the important area signature data may be compared with an assumed pattern, and the best matching pattern may be output as a result.

  Other operations are substantially the same as the operations of the first, second, and third embodiments, and thus redundant description is omitted.

(Effect of 6th Embodiment)
As described above, according to the present embodiment, the following effects can be obtained.
(J) The important area information is not required on the detection side.

  The preferred embodiments of the digital watermark embedding device, the digital watermark verification device, the digital watermark embedding method, and the digital watermark verification method according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. . It will be obvious to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims, and these are naturally within the technical scope of the present invention. It is understood that it belongs.

  For example, in the above embodiment, the fragile digital watermark has been described, but the present invention can also be applied to a robust digital watermark. For example, a case where the third embodiment shown in FIGS. 18 and 19 is applied will be described as an example, and will be described with reference to FIGS. 30 and 31. The signature embedding unit 102 shown in FIG. The signature extraction unit 201 shown in FIG. 19 becomes the message extraction unit 301. The message embedding unit 300 is different from the signature embedding unit 102 shown in FIG. 18 in that only the message is embedded, not the signature data. Further, the message extraction unit 301 is different from the signature extraction unit 201 shown in FIG. 19 in that it extracts only the message, not the signature data. However, the message embedding / extraction method is substantially the same as that of the third embodiment.

  The present invention can be applied to a digital watermark embedding device, a digital watermark verification device, a digital watermark embedding method, and a digital watermark verification method for embedding information in an image.

It is explanatory drawing which shows the structure of the digital watermark embedding apparatus concerning 1st Embodiment. It is explanatory drawing which shows the case where the electronic watermark embedding apparatus of FIG. 3 is applied to a JPEG2000 compressor. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 1st Embodiment. It is explanatory drawing which shows the case where the digital watermark verification apparatus of FIG. 3 is applied to a JPEG2000 decompressor. It is explanatory drawing which shows the signature embedding relationship at the time of important area | region unused. It is explanatory drawing which shows an example of the signature data generation of a block. It is explanatory drawing which shows the relationship between embedding data and the position to embed. It is explanatory drawing which shows the signature embedding relationship of the important area | region and non-important area | region at the time of important region use. It is explanatory drawing which shows the case where the signature data of an important area | region is embedded only in the block around an important area | region. It is a flowchart which shows an example of an embedding process. It is explanatory drawing which shows the outline of a signature embedding position, (a) shows the case where important area signature data is not embedded, and (b) shows the case where important area signature data is embedded. It is explanatory drawing which shows the relationship between a signature data generation source and an embedding position. It is explanatory drawing which shows the electronic watermark embedding side. It is explanatory drawing which shows the structure of the digital watermark embedding apparatus concerning 2nd Embodiment. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 2nd Embodiment. It is explanatory drawing which shows the embedding position of a message. It is explanatory drawing which shows the embedding position of a message. It is explanatory drawing which shows the structure of the digital watermark embedding apparatus concerning 3rd Embodiment. It is explanatory drawing which shows the structure of the electronic watermark verification apparatus concerning 3rd Embodiment. It is explanatory drawing which shows the embedded message division | segmentation method of a block unit. It is explanatory drawing which shows a message coupling | bonding method. It is explanatory drawing which shows the data processing of a message. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 4th Embodiment. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 4th Embodiment. It is explanatory drawing which shows the case where non-important area | region identification information is embedded. It is explanatory drawing which shows the case where a non-important area | region signature data flag is embedded. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 6th Embodiment. It is explanatory drawing which shows the structure of the digital watermark verification apparatus concerning 6th Embodiment. It is explanatory drawing which shows operation | movement of 6th Embodiment. It is explanatory drawing of the digital watermark embedding apparatus at the time of applying 3rd Embodiment to robust digital watermark. It is explanatory drawing of the digital watermark verification apparatus at the time of applying 3rd Embodiment to robust digital watermark. It is explanatory drawing which shows the operation | movement at the time of embedding a fragile digital watermark to a bitmap. It is explanatory drawing which shows the operation | movement at the time of the fragile digital watermark verification to a bitmap.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image data input terminal 2 Important area information input terminal 3 Image data output terminal after embedding 5 Message input terminal 12 Comparison result output terminal 13 Message output terminal 20 Switching part 50 Color conversion part 51 Wavelet conversion part 52 Quantization part 53 Coding part 100 Blocking Unit 101 Signature Generation Unit 110 Message Division Unit 102 Signature Embedding Unit 202 Signature Generation Unit 203 Signature Comparison Unit

Claims (8)

In the digital watermark verification device,
An image input terminal for inputting image data of a target image for verifying the digital watermark;
A blocking unit for dividing the input image data into blocks of a predetermined size;
An important area information input terminal into which important area information related to whether each of the blocks belongs to an important area or a non-important area;
A signature extraction unit for extracting the signature data of the important area and the non -important area from the surrounding non-important area without extracting the signature data from the important area according to the important area information in the block unit; ,
A signature generation unit for generating signature data in the block unit;
A signature comparison unit that compares the signature data extracted by the signature extraction unit with the signature data generated by the signature generation unit;
A comparison result output terminal for outputting a comparison result by the signature comparison unit;
Equipped with a,
The digital watermark verification apparatus , wherein the comparison result output of the signature comparison unit is input to the signature extraction unit . The digital watermark verification apparatus according to claim 1 , wherein the signature extraction unit regards an important area block that is determined to be falsified because signature data does not match by the signature comparison unit as a non-important area block. The digital watermark verification apparatus according to claim 1 , wherein the signature extraction unit regards a non-important region block that has been determined to be falsified because the signature data does not match by the signature comparison unit as an important region block. The signature extraction portion includes a feature that the region surrounded by the block by the important area signed flag embedded in the non-critical regions have been shown to have the signature data for the important region, estimates the importance area The digital watermark verification apparatus according to any one of claims 1 to 3 . A digital watermark verification method,
The image input unit, an image input step of image data of the target image to verify the electronic watermark is input,
A blocking step of dividing the input image data into blocks of a predetermined size by blocking means ;
An important area information input step in which important area information regarding whether each block belongs to an important area or a non-important area is input by an important area information input means;
In the block unit, the signature data is not extracted from the important area according to the important area information, and the signature data of the important area and the non-important area is extracted from the surrounding non-important areas by the signature extracting unit . Signature extraction process;
A signature generation step of generating signature data by the signature generation means in the block unit;
A signature comparison step of comparing the signature data extracted in the signature extraction step with the signature data generated in the signature generation step by a signature comparison unit ;
A comparison result output step of outputting the comparison result of the signature comparison step by a comparison result output means ;
Only including,
The digital watermark verification method, wherein the signature extraction means performs the signature extraction step again using the comparison result output of the signature comparison step . The signature extracting means, in the signature extraction process, characterized in that the critical domain block signature data is determined to be falsified does not coincide in the signature comparison process, regarded as unimportant region block, according to claim 5 Digital watermark verification method. The signature extracting means, in the signature extraction process, characterized in that the non-critical areas block the signature data is determined to be falsified does not coincide in the signature comparison process, regarded as important domain block, according to claim 5 Digital watermark verification method. The signature extracting means, in the signature extraction process, from the region enclosed by the blocks by the important area signed flag embedded in the non-critical regions it has been shown to have the signature data for the important region, the important area The digital watermark verification method according to claim 5 , wherein estimation is performed.

Images