JP4942548B2 - Digital watermark embedding device, digital watermark detection device, digital watermark embedding program, and digital watermark detection program - Google Patents

Description

  The present invention provides, for example, an electronic watermark embedding device and an electronic watermark embedding program for embedding an electronic watermark in an image signal and an audio signal, an electronic watermark detection device and an electronic watermark detection for detecting an electronic watermark embedded in an image signal and an audio signal It is about the program.

2. Description of the Related Art Conventionally, a digital watermark embedding apparatus that embeds a digital watermark in a digital image has been developed so that tampering of the digital image can be detected.
For example, in the digital watermark embedding device disclosed in Patent Document 1 below, a digital image such as JPEG is applied, and the digital image is converted into a frequency domain by DCT (Discrete Cosine Transform).
Then, the digital watermark embedding apparatus quantizes the frequency domain signal, scans the quantized coefficient for each block, rearranges the quantized coefficient in a predetermined order, and then locates the one located immediately after the last non-zero coefficient. By changing the zero coefficient to “+1” or “−1”, 1-bit information is embedded.

However, if the rearranged last coefficient is not “0”, the last coefficient may be forcibly changed to “+1” or “−1”. However, in order to prevent deterioration in image quality, the last coefficient may be changed. Only the coefficient may be changed according to the table shown in FIG.
In this case, if the embedded information is “0”, the coefficient is changed to a value closest to the current value among “..., −5, −3, −1, +2, +4, +6,. From the beginning, if one of these values, you don't have to change it).
If the embedding information is “1”, the current coefficient is set to one of the values “..., −6, −4, −2, +1, +3, +5,.
As a result, the amount of change is at most “1”, so that deterioration in image quality due to embedding of the digital watermark is reduced.

  Here, among a plurality of blocks constituting a digital image, when a block for embedding a digital watermark is determined in advance (for example, when embedding 1-bit information in all blocks, or in order of blocks extracted with random numbers) If the digital watermark embedding device and the digital watermark detection device share information of a predetermined block, the digital watermark detection device can detect the digital watermark embedded by the digital watermark embedding device without error. can do.

However, a signal to be embedded with a digital watermark is generally a signal perceived by humans, such as an image signal or a sound signal, and a digital watermark embedding process for changing the signal regardless of the meaning content of such a signal. In some cases, the signal change may be perceived as subjective deterioration depending on where the digital watermark is embedded.
Therefore, in the digital watermark embedding process, generally, an adaptive process is used in which a part where change is hardly perceived is selected and the digital watermark is embedded in such a part.

Many of these adaptive processes use the masking effect of human perception.
The masking effect is a property in which, if a newly added signal is similar to the original signal, the change is hardly perceived as degradation by masking the original signal.
For this reason, for example, in the case of an image signal, degradation is not noticeable even if the signal is changed by the digital watermark in a portion where the brightness or color changes drastically, but in the portion where the change is slow and flat, the signal is transmitted by the digital watermark. If the change is made, the deterioration will be conspicuous, and it will not be possible to make a very large change.

For example, in Non-Patent Document 1 below, the original signal is decomposed into a plurality of frequency components, the size of the component close to the frequency component of the digital watermark signal is locally calculated, and is close to the frequency component of the digital watermark signal. A technique for controlling the size of a digital watermark signal according to the size of a component is disclosed.
In this way, the method of calculating the local change of the original signal and adjusting the intensity of the distortion so that the distortion introduced by the target signal processing is masked by the original signal is widely used in general image processing. This technique is no exception in the embedding of digital watermarks.

However, the conventional digital watermark embedding apparatus having such embedding control has the following problems.
First, depending on the digital watermark embedding method, the embedded information may be detected even if the embedding location selected by the adaptive processing cannot be accurately specified.
For example, there is a method of decoding embedded information by adding a weak signal not correlated with the original signal to the original signal and detecting the weak signal by correlation.
In such a case, even if there is a slight change in the signal to be added (when the change amount of the signal is partially attenuated by adaptive processing), in many cases, a weak signal can be detected. Is possible.
Further, as in Patent Document 1, even when information is embedded by the state of a part of signals (for example, the signal value of a specific signal defined in a table as shown in FIG. 7), if an error correction method is used, Even if there is a portion that could not be partially embedded by the adaptive processing, it is possible to correctly detect the embedded information with high probability by correcting the error in that portion.

However, any of these methods avoids strict specification of an embedding place in detection of a digital watermark by giving a certain degree of freedom to the embedding method.
This leads to the fact that the digital watermark information is not changed even if the signal after embedding is slightly changed, which is not suitable for the purpose of detecting the alteration of the digital image described at the beginning.
The reason is that it is strictly difficult to distinguish between a change within a range of freedom that does not change the information of the digital watermark and a malicious alteration.
For the purpose of detecting tampering, it is desirable to be able to accurately restore the embedding location from the signal after adaptively embedding, so that even a slight change in the signal can be reliably detected. be able to.

JP 2004-242162 (paragraph numbers [0007] to [0010], FIG. 1) IEEE Journal of selected areas in communication, vol. 16, no. 4, pp. 540-550, May 1998, M. D. Swanson, B. Zhu, and A. H. Tewfik, “Multiresolution Scene-Based Video Watermarking Using Perceptual Models”.

  Since the conventional digital watermark embedding device is configured as described above, the adaptive processing controls whether or not to embed a digital watermark on the basis of the original signal. I do not know the signal before the watermark is embedded. For this reason, the digital watermark detection apparatus has a problem that the position where the digital watermark is embedded cannot be specified accurately and the digital watermark cannot be accurately restored.

The present invention has been made to solve the above-described problems, and a digital watermark embedding apparatus capable of embedding a digital watermark so that the digital watermark detection apparatus can accurately specify the embedding position of the digital watermark. And an electronic watermark embedding program.
Another object of the present invention is to obtain a digital watermark detection apparatus and a digital watermark detection program that can accurately specify the embedding position of a digital watermark embedded by the digital watermark embedding apparatus.

In the digital watermark embedding device according to the present invention, when the number of bits of the digital watermark to be embedded is m bits, the complexity in each block calculated by the complexity calculation means is compared , and the complexity is determined from a plurality of blocks. provided block selecting means for selecting the larger upper m blocks, the electronic watermark embedding means performs Sort signals in the block selected by the block selecting means in a predetermined rule, in the signal after the rearrangement If the last non-zero value signal is not the last signal of the block, the signal value of the next signal after the last non-zero value signal is changed to “+1” or “−1”. By embedding a digital watermark that is 1-bit information of “1” or “0”, if the rearmost non-zero value signal is the last signal in the block, 1 Bi The candidate value closest to the signal value of the last signal is selected from among a plurality of candidate values corresponding to “1” or “0” that is the information of the last signal, and the signal value of the last signal is changed to the above candidate value By doing so, a digital watermark which is 1-bit information of “1” or “0” is embedded .

According to the present invention, when the number of bits of the digital watermark to be embedded is m bits, the complexity in each block calculated by the complexity calculation means is compared, and the top m having the highest complexity from the plurality of blocks. provided the block selecting means for selecting a number of blocks, the electronic watermark embedding means performs Sort signals in the block selected by the block selecting means in a predetermined rule, the rearmost in the signal after the rearrangement If the non-zero value signal is not the last signal of the block, the signal value of the next signal after the last non-zero value signal is changed to “+1” or “−1”, thereby “1”. If the last non-zero signal in the rearranged signal is the last signal in the block after embedding a digital watermark, which is 1-bit information of “0” or “0”, 1-bit information A certain “1” Alternatively, a candidate value closest to the signal value of the last signal is selected from among a plurality of candidate values corresponding to “0”, and the signal value of the last signal is changed to the candidate value, thereby “1”. Alternatively, since the digital watermark which is 1-bit information of “0” is embedded, the digital watermark can be embedded so that the digital watermark detection apparatus can accurately specify the embedded position of the digital watermark. There is.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a digital watermark embedding apparatus according to Embodiment 1 of the present invention. In the figure, a memory 1 inputs a digital signal divided into a plurality of blocks and stores the digital signal. Is configured.
Here, the digital signal corresponds to, for example, an image signal or an audio signal.
Since image signals and audio signals have a strong correlation between spatially adjacent signals, when the signals are converted to the frequency domain, power is concentrated on the low frequency components.
At this time, if the transform coefficient is roughly quantized, many high frequency components are rounded down to “0”. Such a signal is called a sparse signal.
Hereinafter, it is assumed that the digital signal input to the memory 1 is a sparse signal divided into a plurality of blocks.
Note that when converting a digital signal into the frequency domain, DCT (Discrete Cosine Transform), wavelet transform, or the like is generally used.

The complexity calculation unit 2 performs a process of calculating the complexity of each block of the digital signal stored in the memory 1. The complexity calculation unit 2 constitutes complexity calculation means.
The block selection unit 3 compares the complexity in each block calculated by the complexity calculation unit 2 and performs a process of selecting the top m blocks having the highest complexity. The block selecting unit 3 constitutes a block selecting unit.
The digital watermark embedding unit 4 performs a digital watermark embedding process for changing the signal value of a signal at a predetermined position in the block selected by the block selecting unit 3. The digital watermark embedding unit 4 constitutes a digital watermark embedding unit.

  In the example of FIG. 1, the complexity calculation unit 2, the block selection unit 3, and the digital watermark embedding unit 4 which are components of the digital watermark embedding device are each a dedicated hardware (for example, a semiconductor integrated circuit on which a CPU or the like is mounted). In the case where the digital watermark embedding apparatus is configured by a computer, the processing contents of the complexity calculation unit 2, the block selection unit 3, and the digital watermark embedding unit 4 are described. The electronic watermark embedding program may be stored in the memory of a computer, and the CPU of the computer may execute the electronic watermark embedding program stored in the memory.

2 is a block diagram showing a digital watermark detection apparatus according to Embodiment 1 of the present invention. In the figure, a memory 11 inputs a digital signal embedded with a digital watermark by the digital watermark embedding apparatus and stores the digital signal. The signal storage means is configured.
The complexity calculation unit 12 performs a process of calculating the complexity in each block of the digital signal stored in the memory 11. The complexity calculator 12 constitutes a complexity calculator.

The block selection unit 13 compares the complexity in each block calculated by the complexity calculation unit 12, and performs a process of selecting the top m blocks having the highest complexity. The block selecting unit 13 constitutes a block selecting unit.
The digital watermark decoding unit 14 performs a process of decoding the embedded digital watermark from the signal value of the signal at a predetermined position in the block selected by the block selection unit 13. The digital watermark decoding unit 14 constitutes a digital watermark decoding unit.

  In the example of FIG. 2, the complexity calculator 12, the block selector 13, and the digital watermark decoder 14, which are components of the digital watermark detection apparatus, each have dedicated hardware (for example, a semiconductor integrated circuit on which a CPU or the like is mounted). In the case where the digital watermark detection apparatus is configured by a computer, processing contents of the complexity calculation unit 12, the block selection unit 13, and the digital watermark decoding unit 14 are described. The electronic watermark detection program stored in the computer may be stored in the memory of the computer, and the CPU of the computer may execute the electronic watermark detection program stored in the memory.

FIG. 3 is a flowchart showing the processing contents of the digital watermark embedding apparatus according to Embodiment 1 of the present invention.
FIG. 4 is a flowchart showing the processing contents of the digital watermark detection apparatus according to Embodiment 1 of the present invention.

Next, the operation will be described.
First, a digital watermark embedding process by the digital watermark embedding apparatus in FIG. 1 will be described.
When a digital signal, which is a sparse signal divided into a plurality of blocks, is input to the digital watermark embedding device, the digital signal is stored in the memory 1 (step ST1 in FIG. 3).

When the digital signal is stored in the memory 1, the complexity calculating unit 2 calculates the complexity of the block for each block of the digital signal (step ST2).
Hereinafter, the complexity calculation process in each block will be described in detail.
Here, it is assumed that the block size of a digital signal that is a sparse signal is 8 × 8, for example.

The complexity calculation unit 2 quantizes a digital signal that is a sparse signal. For example, when the digital signal is converted into the frequency domain by DCT, the quantization coefficient is read in the scan order as shown in FIG. I do.
Here, the quantization coefficient at the upper left in FIG. 5 has a lower frequency, and the frequency becomes higher as it goes to the lower right.
For example, since a digital signal such as an image signal has low high-frequency power, when the signals are arranged in the order shown in FIG. 5, in many cases, all signal values become “0” above a certain level. Become.
The complexity calculation unit 2 assumes that the complexity of the block is “n” if the last non-zero quantization coefficient appears nth and all of the nth and subsequent quantization coefficients are “0”. .

Further, when the digital signal that is a sparse signal is converted into the frequency domain by, for example, wavelet transform, the complexity calculation unit 2 reads out the quantization coefficients in the scan order as illustrated in FIG.
In the case of the wavelet transform, generally, the transform is not closed in a block, but even in that case, spatially close quantization coefficients can be collectively divided into blocks.
In the example of FIG. 6 as well, scanning is performed in order from the lower left component having a low frequency. However, in the wavelet transform, the high frequency components are roughly divided, so that the scanning order is different from that in the case of DCT.
Also in the case of the wavelet transform, if the last non-zero quantization coefficient appears nth and all the nth and subsequent quantization coefficients are all “0”, the complexity of the block is assumed to be “n”.

  The complexity calculation unit 2 calculates the complexity of each block as described above. Even when a digital signal, which is a sparse signal, is converted to the frequency domain by DCT, it is converted to the frequency domain by wavelet conversion. Even in the case of conversion, if the scan order is determined in advance, the complexity of the block can be uniquely determined.

When the complexity calculator 2 calculates the complexity of each block, the block selector 3 compares the complexity of each block and selects the block with the highest m complexity (step ST3).
However, when the number of signals in the block is N (N = 64 when the block size is 8 × 8), the block selection unit 3 has a complexity N block (a block with the maximum complexity). And a block with complexity N−1 are treated as having the same complexity. In addition, for blocks with the same complexity, the block with the earlier search order is preferentially selected.
Hereinafter, the block selection process in the block selection unit 3 will be described in detail.

The block selection unit 3 sequentially assigns numbers 1 to k to all the blocks, and sorts the blocks in descending order of complexity calculated by the complexity calculation unit 2.
Details of the sorting are as follows.
However, the i-th block is denoted as Bi, the j-th block is denoted as Bj, the complexity of the block Bi is denoted as C (Bi), and the complexity of the block Bj is denoted as C (Bj).

The block selection unit 3 rearranges the blocks B1 to Bk so that the block Bi and the block Bj satisfy the following relationship.
(1) When min (C (Bi), N-1)> min (C (Bj), N-1) → The order of block Bi is set higher than that of block Bj (2) min (C (Bi ), N-1) = min (C (Bj), N-1) i <j → rank block Bi higher than block Bj i ≧ j → rank block Bi rank block Bj (3) min (C (Bi), N-1) <min (C (Bj), N-1)
→ The order of the block Bi is made lower than the order of the block Bj. However, min (A, B) is an operator indicating that the smaller one of A and B is selected.

In the above block sorting, a block having a higher complexity ranks higher than a block having a lower complexity.
However, if the complexity of the block Bi is N (maximum complexity) and the complexity of the block Bj is N-1, the complexity is sorted as having the same value.
When the complexity of the two blocks Bi and Bj is the same, the block with the smaller number (the block with the earlier search order) has a higher rank.

When the block selection unit 3 rearranges the blocks B1 to Bk, the block selection unit 3 selects blocks having ranks “1” to “m”. m is the number of bits of information for embedding a digital watermark.
Here, FIG. 8 is an explanatory diagram showing a numerical example of the complexity of each block calculated by the complexity calculator 2, and FIG. 8 shows an example in which the total number of blocks is 10.
FIG. 9 is an explanatory diagram showing a sorting result by the block selection unit 3.
In FIG. 9, the reason why the ranks of the blocks B6 and B7 are higher than the rank of the block B8 is that the complexity of the block B8 is 64 (= N) and the complexity of the blocks B6 and B7 is 63 (= N−1). = 64-1), the complexity of the blocks B6, B7, and B8 is treated as the same value, and the block with the smaller number is arranged so that the rank is higher.

For example, when embedding information with a bit number of m = 5, the block selection unit 3 selects blocks B3, B6, B7, B8, and B2 as the upper five blocks.
Note that the block selection unit 3 only needs to select the top m blocks, and therefore the sorting need not be performed for all blocks. If the sort process is limited to the top m blocks, the process of the block selector 3 can be simplified.

When the block selection unit 3 selects the upper m blocks, the digital watermark embedding unit 4 performs an electronic watermark embedding process for changing the signal value of a signal at a predetermined position in the upper m blocks (step ST4).
In other words, the digital watermark embedding unit 4 rearranges the quantization coefficients in the block for each block selected by the block selection unit 3 according to a certain rule (for example, rearranges in the scan order of FIGS. 5 and 6). I do).

Then, if the last non-zero quantization coefficient is not the last quantization coefficient of the block, the digital watermark embedding unit 4 determines the next quantization coefficient after the last non-zero quantization coefficient. By changing to “+1” or “−1”, 1-bit information is embedded.
On the other hand, if the last non-zero quantization coefficient is the last quantization coefficient of the block, only the last quantization coefficient of the block is changed according to the table shown in FIG.
In this case, if the embedded information is “0”, the quantization coefficient is a value closest to the current quantization coefficient among “..., −5, −3, −1, +2, +4, +6,. (From the beginning, if it is one of these values, you do not need to change it.)
If the embedded information is “1”, the current quantization coefficient is set to one of the values “..., −6, −4, −2, +1, +3, +5,.

In the digital watermark embedding process by the digital watermark embedding unit 4, the complexity of the block increases only by “1” at most.
That is, when the quantization coefficient in which the digital watermark is embedded is not the last quantization coefficient of the block, the complexity increases by “1”, and the quantization coefficient in which the digital watermark is embedded becomes the quantization coefficient at the end of the block. The complexity does not change.
For this reason, the block selected by the block selection unit 3 from the block after the digital watermark is embedded can be accurately specified together with the order.

The reason is that if all the complexity levels of the blocks selected by the block selection unit 3 are N, the block selected by the block selection unit 3 can be identified by referring to the block number.
For example, in the block selected by the block selection unit 3, when the complexity before embedding the digital watermark is N-1, the complexity becomes N by embedding the digital watermark.
At this time, the block selection unit 3 sorts the blocks with complexity N and N-1 as having the same complexity, so if the blocks with complexity N are selected in the order of the block numbers, The block selected by the block selector 3 can be specified, and the order of the selected blocks can be specified.
In addition, when a block having a complexity level of N-2 or less before being embedded is selected, the order does not change before and after the embedding, so that it can be specified.

FIG. 10 is an explanatory diagram showing a change in complexity before and after the digital watermark is embedded.
In the example of FIG. 10, digital watermarks are embedded in the top five blocks, and the complexity of blocks B3 and B8 is already 64 before embedding, so there is no change in complexity due to watermark embedding.
When attention is paid to the complexity after embedding the digital watermark, the complexity of the blocks B3, B6, B7, and B8 is 64. Therefore, if the blocks B3, B6, B7, and B8 are arranged in the order of the block numbers, the first place To the 4th place are determined (1st place: block B3, 2nd place: block B6, 3rd place: block B7, 4th place: block B8).
Note that the fifth block is the block B2 having the next highest complexity.

  The block in which the digital watermark is embedded by the digital watermark embedding unit 4 is written in the memory 1, and then all the blocks including the block in which the digital watermark is embedded are read from the memory 1 (step ST5).

Next, digital watermark detection processing by the digital watermark detection apparatus in FIG. 2 will be described.
When a digital signal that is a sparse signal divided into a plurality of blocks is input to the digital watermark detection apparatus, the digital signal is stored in the memory 11 (step ST11 in FIG. 4).

  When the digital signal is stored in the memory 11, the complexity calculation unit 12 calculates the complexity of the block for each block of the digital signal in the same manner as the complexity calculation unit 2 of the digital watermark embedding apparatus. (Step ST12).

When the complexity calculation unit 12 calculates the complexity of each block, the block selection unit 13 compares the complexity of each block and selects the block having the highest complexity (step ST13).
Hereinafter, the block selection process in the block selection unit 3 will be described in detail.

The block selection unit 13 assigns numbers 1 to k to all the blocks in order (block numbers are assigned according to the same rules as when embedding), and blocks are added in descending order of complexity calculated by the complexity calculation unit 12. Sort.
Details of the sorting are as follows.
However, the i-th block is denoted as Bi, the j-th block is denoted as Bj, the complexity of the block Bi is denoted as C (Bi), and the complexity of the block Bj is denoted as C (Bj).

The block selection unit 13 rearranges the blocks B1 to Bk so that the block Bi and the block Bj satisfy the following relationship.
(1) C (Bi)> C (Bj)
→ The order of block Bi is made higher than the order of block Bj (2) When C (Bi) = C (Bj) i <j → The order of block Bi is made higher than the order of block Bj i ≧ j → block The order of Bi is made lower than the order of block Bj. (3) C (Bi) <C (Bj)
→ Lower the rank of block Bi below the rank of block Bj

Note that, unlike the block selection unit 3 of the digital watermark embedding device, the block selection unit 13 does not classify blocks with complexity N and N−1 into the same complexity, and therefore, in the rearrangement rule, the operator min () Not using.
The reason why the block selection unit 13 can accurately specify (including specification of the order) the block selected by the block selection unit 3 of the digital watermark embedding apparatus is as described above.

When the block selection unit 13 selects the upper m blocks, the digital watermark decoding unit 14 performs a process of decoding the embedded watermark from the signal value of the signal at a predetermined position in the upper m blocks (step ST15). ).
That is, the digital watermark decoding unit 14 rearranges the quantized coefficients in the block using the same rule as the digital watermark embedding unit 4 of the digital watermark embedding device. That is, for each block selected by the block selection unit 13, the quantization coefficients in the block are rearranged, for example, in the scan order of FIGS.

When the digital watermark decoding unit 14 rearranges the quantization coefficients in the block, the digital watermark decoding unit 14 determines whether the information embedded by the digital watermark embedding apparatus is “0” or 1 based on the value of the last non-zero quantization coefficient. To do.
The digital watermark decoding unit 14 repeatedly performs the above-described determination process for the number of blocks selected by the block selection unit 13 and outputs the determination result as an m-bit binary signal (decoded signal of the digital watermark).

Here, the entire digital signal has been described as being stored in the memory 11. However, unlike the case of embedding a digital watermark, it is not necessary to read it again as a meaningful signal from the memory 11. Only the minimum necessary information may be held in the memory 11.
For example, after the complexity of a block is calculated, storing the complexity value and the last non-zero quantization coefficient of the block is sufficient for detecting a digital watermark.

  As is apparent from the above, according to the first embodiment, the block selection unit 3 that compares the complexity in each block calculated by the complexity calculation unit 2 and selects the block with the highest m complexity. Since the digital watermark embedding unit 4 performs the digital watermark embedding process for changing the signal value of the signal at the predetermined position in the block selected by the block selecting unit 3, the digital watermark detecting apparatus There is an effect that a digital watermark can be embedded so that the embedded position can be accurately specified.

  Further, according to the first embodiment, the block selection unit 13 that compares the complexity in each block calculated by the complexity calculation unit 12 and selects the m blocks with the highest complexity is provided. Since the watermark decoding unit 14 is configured to decode the digital watermark embedded from the signal value of the signal at the predetermined position in the block selected by the block selection unit 13, the embedded position of the digital watermark embedded by the digital watermark embedding device It is possible to accurately identify the digital watermark and accurately decode the digital watermark.

Embodiment 2. FIG.
In the first embodiment, the complexity calculation units 2 and 12 have been described as calculating the number of blocks from the first quantization coefficient in the block to the last non-zero quantization coefficient as the complexity of the block. The number of non-zero quantization coefficients in the block may be counted, and the number of non-zero quantization coefficients in the block may be calculated as the complexity of the block.
Also in this case, the digital watermark embedding apparatus can increase the complexity only by 1, so that the same effect as in the first embodiment can be obtained.

1 is a configuration diagram illustrating a digital watermark embedding device according to a first embodiment of the present invention. It is a block diagram which shows the digital watermark detection apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the digital watermark embedding apparatus by Embodiment 1 of this invention. It is a flowchart which shows the processing content of the digital watermark detection apparatus by Embodiment 1 of this invention. It is explanatory drawing which shows the scan order of the quantization coefficient in case the digital signal which is a sparse signal is converted into the frequency domain by DCT. It is explanatory drawing which shows the scan order of the quantization coefficient in case the digital signal which is a sparse signal is converted into the frequency domain by wavelet transform. It is explanatory drawing which shows the value of the embedding information and the quantized coefficient. It is explanatory drawing which shows the numerical example of the complexity of each block calculated by the complexity calculation part 2. FIG. It is explanatory drawing which shows the sorting result by the block selection part 3. FIG. It is explanatory drawing which shows the change of the complexity before and behind a digital watermark being embedded.

Explanation of symbols

  1, 11 memory (signal storage means), 2, 12 complexity calculation section (complexity calculation means), 3, 13 block selection section (block selection means), 4 digital watermark embedding section (digital watermark embedding means), 14 electrons Watermark decoding unit (digital watermark decoding means).

Claims (8)

A signal storage means for storing a signal divided into a plurality of blocks; a complexity calculation means for calculating complexity indicating an complexity of each block of the signal stored in the signal storage means; and an embedded digital watermark When the number of bits of m is m bits, a block that compares the complexity in each block calculated by the complexity calculation means and selects the top m blocks having the highest complexity from the plurality of blocks The selection means and the signals in the block selected by the block selection means are rearranged according to a certain rule, and the rearmost non-zero signal in the rearranged signal is the last signal of the block. Otherwise, by changing the signal value of the signal next to the last non-zero value signal to “+1” or “−1”, an electronic signal that is 1-bit information of “1” or “0” Transparency If the last non-zero signal in the rearranged signal is the last signal of the block, a plurality of bits corresponding to 1-bit information “1” or “0” By selecting the candidate value closest to the signal value of the last signal from the candidate values and changing the signal value of the last signal to the candidate value, a 1-bit “1” or “0” is obtained. An electronic watermark embedding apparatus comprising an electronic watermark embedding unit for embedding an electronic watermark as information . When the signal divided into a plurality of blocks is an image signal or an audio signal, the complexity calculation means determines the number of blocks from the first signal in the block to the last non-zero value as the complexity of the block. 2. The digital watermark embedding apparatus according to claim 1, wherein the number from the first signal to the last non-zero value signal is counted. When the signal divided into the plurality of blocks is an image signal or an audio signal, the complexity calculation means determines that the number of signals having non-zero signal values in the block is the complexity of the block. 2. The digital watermark embedding apparatus according to claim 1, wherein the number of signals having non-zero signal values is counted. When the number of signals in the block is N, the block selecting means regards that the complexity is the same as the block having the complexity N and the block having the complexity N-1, and the complexity is the same. 4. The digital watermark embedding apparatus according to claim 2, wherein a block having a small preset number is preferentially selected for the block. Embedded in a signal storage means for storing a signal divided into a plurality of blocks, a complexity calculation means for calculating a complexity which is an index indicating the complexity of each block of the signal stored in the signal storage means, and embedded When the number of bits of the digital watermark is m bits, the complexity in each block calculated by the complexity calculation means is compared, and the top m blocks with the highest complexity are selected from the plurality of blocks The block selection means to be used and the signals in the block selected by the block selection means are rearranged according to a certain rule, and are embedded from the signal value of the rearmost non-zero value signal in the rearranged signals. An electronic watermark detection apparatus comprising: an electronic watermark decoding unit that decodes the electronic watermark. 6. The digital watermark detection apparatus according to claim 5 , wherein the block selection means preferentially selects a block having a smaller preset number for blocks having the same complexity calculated by the complexity calculation means. . A signal storage processing procedure for storing a signal divided into a plurality of blocks, a complexity calculation processing procedure for calculating a complexity that is an index indicating the complexity of each block of the signal stored by the signal storage processing procedure, When the number of bits of the digital watermark to be embedded is m bits, the complexity of each block calculated by the complexity calculation processing procedure is compared, and the top m blocks having the highest complexity from the plurality of blocks The block selection processing procedure for selecting and the signals in the block selected by the block selection processing procedure are rearranged according to a certain rule, and the rearmost non-zero signal in the rearranged signal is If it is not the last signal of the block, the signal value of the next signal after the last non-zero value signal is changed to “+1” or “−1”, thereby “1” or “0”. If an electronic watermark that is 1-bit information is embedded and the rearmost non-zero value signal in the rearranged signal is the last signal of the block, 1-bit information “1” or “1” By selecting a candidate value closest to the signal value of the last signal from among a plurality of candidate values corresponding to “0”, and changing the signal value of the last signal to the candidate value, “1” or An electronic watermark embedding program for causing a computer to execute an electronic watermark embedding process procedure for embedding an electronic watermark that is 1-bit information of “0” . A signal storage processing procedure for storing a signal divided into a plurality of blocks, a complexity calculation processing procedure for calculating a complexity that is an index indicating the complexity of each block of the signal stored by the signal storage processing procedure, When the number of bits of the embedded digital watermark is m bits, the complexity in each block calculated by the complexity calculation processing procedure is compared, and the top m blocks having the highest complexity from the plurality of blocks The block selection processing procedure for selecting the block and the signals in the block selected by the block selection processing procedure are rearranged according to a certain rule, and the rearmost non-zero signal in the rearranged signal A digital watermark detection program for causing a computer to execute a digital watermark decoding processing procedure for decoding a digital watermark embedded from the signal value of the digital watermark.

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